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Date:   Thu, 3 Nov 2016 04:53:16 +0000
From:   Vadim Pasternak <vadimp@...lanox.com>
To:     Vladimir Zapolskiy <vz@...ia.com>,
        "wsa@...-dreams.de" <wsa@...-dreams.de>
CC:     "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        Michael Shych <michaelsh@...lanox.com>
Subject: RE: [patch v2] i2c: add master driver for mellanox systems



> -----Original Message-----
> From: Vladimir Zapolskiy [mailto:vz@...ia.com]
> Sent: Thursday, November 03, 2016 1:09 AM
> To: Vadim Pasternak <vadimp@...lanox.com>; wsa@...-dreams.de
> Cc: linux-i2c@...r.kernel.org; linux-kernel@...r.kernel.org; jiri@...nulli.us;
> Michael Shych <michaelsh@...lanox.com>
> Subject: Re: [patch v2] i2c: add master driver for mellanox systems
> 
> Hi Vadim,

Hi Vladimir,

Thank you very much for you review.

> 
> On 19.09.2016 18:00, vadimp@...lanox.com wrote:
> > From: Vadim Pasternak <vadimp@...lanox.com>
> >
> > Device driver for Mellanox I2C controller logic, implemented in
> > Lattice CPLD device.
> > Device supports:
> >  - Master mode
> >  - One physical bus
> >  - Polling mode
> >
> > The Kconfig currently controlling compilation of this code is:
> > drivers/i2c/busses/Kconfig:config I2C_MLXCPLD
> >
> > Signed-off-by: Michael Shych <michaelsh@...lanox.com>
> > Signed-off-by: Vadim Pasternak <vadimp@...lanox.com>
> > Reviewed-by: Jiri Pirko <jiri@...lanox.com>
> > v1->v2
> >  Fixes added by Vadim:
> >  - Put new record in Makefile in alphabetic order;
> >  - Remove http://www.mellanox.com from MAINTAINERS record;
> 
> the change does not apply cleanly on top of the recent source, please consider
> to rebase it.

I suppose this is because the patch has been sent quite long time ago and it was created in 4.8 i2c/for-next. I'll redo it in latest i2c/for-next branch.
I suppose this is also the reason of checkpatch warnings, since it passed clean the validation in 4.8.

> 
> Anyway please consider to check some review points found below.
> 
> > ---
> >  Documentation/i2c/busses/i2c-mlxcpld |  47 +++
> >  MAINTAINERS                          |   8 +
> >  drivers/i2c/busses/Kconfig           |  12 +
> >  drivers/i2c/busses/Makefile          |   1 +
> >  drivers/i2c/busses/i2c-mlxcpld.c     | 597
> +++++++++++++++++++++++++++++++++++
> >  5 files changed, 665 insertions(+)
> >  create mode 100644 Documentation/i2c/busses/i2c-mlxcpld
> >  create mode 100644 drivers/i2c/busses/i2c-mlxcpld.c
> >
> > diff --git a/Documentation/i2c/busses/i2c-mlxcpld
> > b/Documentation/i2c/busses/i2c-mlxcpld
> > new file mode 100644
> > index 0000000..0f8678a
> > --- /dev/null
> > +++ b/Documentation/i2c/busses/i2c-mlxcpld
> > @@ -0,0 +1,47 @@
> > +Driver i2c-mlxcpld
> > +
> > +Author: Michael Shych <michaelsh@...lanox.com>
> > +
> > +This is a for Mellanox I2C controller logic, implemented in Lattice
> > +CPLD device.
> > +Device supports:
> > + - Master mode.
> > + - One physical bus.
> > + - Polling mode.
> > +
> > +This controller is equipped within the next Mellanox systems:
> > +"msx6710", "msx6720", "msb7700", "msn2700", "msx1410", "msn2410",
> > +"msb7800", "msn2740", "msn2100".
> > +
> > +The next transaction types are supported:
> > + - Receive Byte/Block.
> > + - Send Byte/Block.
> > + - Read Byte/Block.
> > + - Write Byte/Block.
> > +
> > +Registers:
> > +CTRL		0x1 - control reg.
> > +			Resets all the registers.
> > +HALF_CYC	0x4 - cycle reg.
> > +			Configure the width of I2C SCL half clock cycle (in 4
> LPC_CLK
> > +			units).
> > +I2C_HOLD	0x5 - hold reg.
> > +			OE (output enable) is delayed by value set to this
> register
> > +			(in LPC_CLK units)
> > +CMD			0x6 - command reg.
> > +			Bit 7(lsb), 0 = write, 1 = read.
> > +			Bits [6:0] - the 7bit Address of the I2C device.
> > +			It should be written last as it triggers an I2C transaction.
> > +NUM_DATA	0x7 - data size reg.
> > +			Number of address bytes to write in read transaction
> > +NUM_ADDR	0x8 - address reg.
> > +			Number of address bytes to write in read transaction.
> > +STATUS		0x9 - status reg.
> > +			Bit 0 - transaction is completed.
> > +			Bit 4 - ACK/NACK.
> > +DATAx		0xa - 0x54  - 68 bytes data buffer regs.
> > +			For write transaction address is specified in four first
> bytes
> > +			(DATA1 - DATA4), data starting from DATA4.
> > +			For read transactions address is send in separate
> transaction and
> > +			specified in four first bytes (DATA0 - DATA3). Data is
> reading
> > +			starting from DATA0.
> > diff --git a/MAINTAINERS b/MAINTAINERS index 6781a3f..dc31231 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -7667,6 +7667,14 @@ W:	http://www.mellanox.com
> >  Q:	http://patchwork.ozlabs.org/project/netdev/list/
> >  F:	drivers/net/ethernet/mellanox/mlxsw/
> >
> > +MELLANOX MLXCPLD I2C DRIVER
> > +M:	Vadim Pasternak <vadimp@...lanox.com>
> > +M:	Michael Shych <michaelsh@...lanox.com>
> > +L:	linux-i2c@...r.kernel.org
> > +S:	Supported
> > +F:	drivers/i2c/busses/i2c-mlxcpld.c
> > +F:	Documentation/i2c/busses/i2c-mlxcpld
> > +
> >  SOFT-ROCE DRIVER (rxe)
> >  M:	Moni Shoua <monis@...lanox.com>
> >  L:	linux-rdma@...r.kernel.org
> > diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> > index 5c3993b..1126142a 100644
> > --- a/drivers/i2c/busses/Kconfig
> > +++ b/drivers/i2c/busses/Kconfig
> > @@ -1203,4 +1203,16 @@ config I2C_OPAL
> >  	  This driver can also be built as a module. If so, the module will be
> >  	  called as i2c-opal.
> >
> > +config I2C_MLXCPLD
> > +        tristate "Mellanox I2C driver"
> > +        depends on X86_64
> > +        default y
> > +        help
> 
> Please use one tab symbol as indentation above.
> 
> Please add the section preserving the alphabetical order.
> 
> > +	  This exposes the Mellanox platform I2C busses to the linux I2C layer
> > +	  for X86 based systems.
> > +	  Controller is implemented as CPLD logic.
> > +
> > +	  This driver can also be built as a module. If so, the module will be
> > +	  called as i2c-mlxcpld.
> > +
> >  endmenu
> > diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> > index 37f2819..4df3578 100644
> > --- a/drivers/i2c/busses/Makefile
> > +++ b/drivers/i2c/busses/Makefile
> > @@ -118,5 +118,6 @@ obj-$(CONFIG_I2C_PCA_ISA)	+= i2c-pca-isa.o
> >  obj-$(CONFIG_I2C_SIBYTE)	+= i2c-sibyte.o
> >  obj-$(CONFIG_I2C_XGENE_SLIMPRO) += i2c-xgene-slimpro.o
> >  obj-$(CONFIG_SCx200_ACB)	+= scx200_acb.o
> > +obj-$(CONFIG_I2C_MLXCPLD)	+= i2c-mlxcpld.o
> 
> Please add the line preserving the alphabetical order.
> 
> >
> >  ccflags-$(CONFIG_I2C_DEBUG_BUS) := -DDEBUG diff --git
> > a/drivers/i2c/busses/i2c-mlxcpld.c b/drivers/i2c/busses/i2c-mlxcpld.c
> > new file mode 100644
> > index 0000000..dd62190
> > --- /dev/null
> > +++ b/drivers/i2c/busses/i2c-mlxcpld.c
> > @@ -0,0 +1,597 @@
> > +/*
> > + * drivers/i2c/busses/i2c-mlxcpld.c
> > + * Copyright (c) 2016 Mellanox Technologies. All rights reserved.
> > + * Copyright (c) 2016 Michael Shych <michaels@...lanox.com>
> > + *
> > + * Redistribution and use in source and binary forms, with or without
> > + * modification, are permitted provided that the following conditions are
> met:
> > + *
> > + * 1. Redistributions of source code must retain the above copyright
> > + *    notice, this list of conditions and the following disclaimer.
> > + * 2. Redistributions in binary form must reproduce the above copyright
> > + *    notice, this list of conditions and the following disclaimer in the
> > + *    documentation and/or other materials provided with the distribution.
> > + * 3. Neither the names of the copyright holders nor the names of its
> > + *    contributors may be used to endorse or promote products derived from
> > + *    this software without specific prior written permission.
> > + *
> > + * Alternatively, this software may be distributed under the terms of
> > +the
> > + * GNU General Public License ("GPL") version 2 as published by the
> > +Free
> > + * Software Foundation.
> > + *
> > + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
> CONTRIBUTORS "AS IS"
> > + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
> LIMITED
> > +TO, THE
> > + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
> PARTICULAR
> > +PURPOSE
> > + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
> > +CONTRIBUTORS BE
> > + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
> > +OR
> > + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
> PROCUREMENT
> > +OF
> > + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
> > +BUSINESS
> > + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
> > +WHETHER IN
> > + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
> > +OTHERWISE)
> > + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
> > +ADVISED OF THE
> > + * POSSIBILITY OF SUCH DAMAGE.
> 
> So the code is dual licensed under BSD 3-Clause / GPLv2.
> 
> > + */
> > +
> > +#include <linux/delay.h>
> > +#include <linux/i2c.h>
> > +#include <linux/init.h>
> > +#include <linux/io.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/platform_device.h>
> > +
> > +/* General defines */
> > +#define MLXPLAT_CPLD_LPC_I2C_BASE_ADRR	0x2000
> 
> s/ADRR/ADDR/
> 
> > +#define MLXCPLD_I2C_DEVICE_NAME		"i2c_mlxcpld"
> > +#define MLXCPLD_I2C_VALID_FLAG		(I2C_M_RECV_LEN |
> I2C_M_RD)
> > +#define MLXCPLD_I2C_BUS_NUM		1
> > +#define MLXCPLD_I2C_DATA_REG_SZ		36
> > +#define MLXCPLD_I2C_MAX_ADDR_LEN	4
> > +#define MLXCPLD_I2C_RETR_NUM		2
> > +#define MLXCPLD_I2C_XFER_TO		500000 /* msec */
> > +#define MLXCPLD_I2C_POLL_TIME		2000   /* msec */
> > +
> > +/* LPC I2C registers */
> > +#define MLXCPLD_LPCI2C_LPF_REG		0x0
> > +#define MLXCPLD_LPCI2C_CTRL_REG		0x1
> > +#define MLXCPLD_LPCI2C_HALF_CYC_REG	0x4
> > +#define MLXCPLD_LPCI2C_I2C_HOLD_REG	0x5
> > +#define MLXCPLD_LPCI2C_CMD_REG		0x6
> > +#define MLXCPLD_LPCI2C_NUM_DAT_REG	0x7
> > +#define MLXCPLD_LPCI2C_NUM_ADDR_REG	0x8
> > +#define MLXCPLD_LPCI2C_STATUS_REG	0x9
> > +#define MLXCPLD_LPCI2C_DATA_REG		0xa
> > +
> > +/* LPC I2C masks and parametres */
> > +#define MLXCPLD_LPCI2C_RST_SEL_MASK	0x1
> 
> This macro is not used.
> 
> > +#define MLXCPLD_LPCI2C_LPF_DFLT		0x2
> 
> This macro is not used.
> 
> > +#define MLXCPLD_LPCI2C_HALF_CYC_100	0x1f
> 
> This macro is not used.
> 
> > +#define MLXCPLD_LPCI2C_I2C_HOLD_100	0x3c
> 
> This macro is not used.
> 
> > +#define MLXCPLD_LPCI2C_TRANS_END	0x1
> > +#define MLXCPLD_LPCI2C_STATUS_NACK	0x10
> 
> This macro is not used.
> 
> > +#define MLXCPLD_LPCI2C_ERR_IND		-1
> 
> This macro is not used.
> 
> > +#define MLXCPLD_LPCI2C_NO_IND		0
> > +#define MLXCPLD_LPCI2C_ACK_IND		1
> > +#define MLXCPLD_LPCI2C_NACK_IND		2
> > +
> > +/**
> > + * mlxcpld_i2c_regs - controller registers:
> > + * @half_cyc - half cycle register
> > + * @i2c_hold - hold register
> > + * @config - config register
> > + * @cmd - command register
> > + * @cmd - status register
> > + * @data - register data
> > +**/
> 
> checkpatch warning:
> 
> WARNING: Block comments should align the * on each line
> #85: FILE: drivers/i2c/busses/i2c-mlxcpld.c:85:
> + * @data - register data
> +**/
> 
> Also for improving readability please add an empty line before the following
> struct declaration.
> 
> > +struct mlxcpld_i2c_regs {
> > +	u8 half_cyc;
> > +	u8 i2c_hold;
> > +	u8 config;
> > +	u8 cmd;
> > +	u8 status;
> > +	u8 data[MLXCPLD_I2C_DATA_REG_SZ];
> > +};
> > +
> 
> This structure is not used, please remove it.
> 
> > +/**
> > + * mlxcpld_i2c_curr_transf - current transaction parameters:
> > + * @cmd - command
> > + * @addr_width - address width
> > + * @data_len - data length
> > + * @cmd - command register
> > + * @msg_num - message number
> > + * @msg - pointer to message buffer
> > +**/
> 
> checkpatch warning:
> 
> WARNING: Block comments should align the * on each line
> #103: FILE: drivers/i2c/busses/i2c-mlxcpld.c:103:
> + * @msg - pointer to message buffer
> +**/
> 
> Also for improving readability please add an empty line before the following
> struct declaration.
> 
> > +struct mlxcpld_i2c_curr_transf {
> > +	u8 cmd;
> > +	u8 addr_width;
> > +	u8 data_len;
> > +	u8 msg_num;
> > +	struct i2c_msg *msg;
> > +};
> > +
> > +/**
> > + * mlxcpld_i2c_priv - private controller data:
> > + * @lpc_gen_dec_reg - register space
> > + * @adap - i2c adapter
> > + * @dev_id - device id
> > + * @base_addr - base IO address
> > + * @poll_time - polling time
> > + * @xfer_to - transfer timeout in microsec (500000)
> > + * @retr_num - access retries number (2)
> > + * @block_sz - maximum data block size (36),
> > + * @lock - bus access lock
> > + * @lpc_i2c_res - lpc i2c resourse
> > + * @lpc_cpld_res - lpc cpld resource
> > + * @xfer - current i2c transfer block
> > + * @pdev - platform device
> > +**/
> 
> WARNING: Block comments should align the * on each line
> #127: FILE: drivers/i2c/busses/i2c-mlxcpld.c:127:
> + * @pdev - platform device
> +**/
> 
> Also for improving readability please add an empty line before the following
> struct declaration.
> 
> > +struct mlxcpld_i2c_priv {
> > +	struct i2c_adapter adap;
> > +	u16 dev_id;
> > +	u16 base_addr;
> > +	u16 poll_time;
> > +	int xfer_to;
> > +	int retr_num;
> 
> Remove 'retr_num', set MLXCPLD_I2C_RETR_NUM directly.
> 
> Alsoe see my comment for .probe() function.
> 
> > +	int block_sz;
> > +	struct mutex lock;
> > +	struct mlxcpld_i2c_curr_transf xfer;
> > +	struct platform_device *pdev;
> > +};
> 
> checkpatch complains:
> 
> CHECK: Please use a blank line after function/struct/union/enum declarations
> #140: FILE: drivers/i2c/busses/i2c-mlxcpld.c:140:
> +};
> +struct platform_device *mlxcpld_i2c_plat_dev;
> 
> > +struct platform_device *mlxcpld_i2c_plat_dev;
> > +
> > +static void mlxcpld_i2c_lpc_write_buf(u8 *data, u8 len, u32 addr) {
> > +	int i, nbyte, ndword;
> > +
> > +	nbyte = len % 4;
> > +	ndword = len / 4;
> > +	for (i = 0; i < ndword; i++)
> > +		outl(*((u32 *)data + i), addr + i * 4);
> > +	ndword *= 4;
> > +	addr += ndword;
> > +	data += ndword;
> > +	for (i = 0; i < nbyte; i++)
> > +		outb(*(data + i), addr + i);
> > +}
> > +
> > +static void mlxcpld_i2c_lpc_read_buf(u8 *data, u8 len, u32 addr) {
> > +	int i, nbyte, ndword;
> > +
> > +	nbyte = len % 4;
> > +	ndword = len / 4;
> > +	for (i = 0; i < ndword; i++)
> > +		*((u32 *)data + i) = inl(addr + i * 4);
> > +	ndword *= 4;
> > +	addr += ndword;
> > +	data += ndword;
> > +	for (i = 0; i < nbyte; i++)
> > +		*(data + i) = inb(addr + i);
> > +}
> > +
> > +static void mlxcpld_i2c_read_comm(struct mlxcpld_i2c_priv *priv, u8 offs,
> > +				  u8 *data, u8 datalen)
> > +{
> > +	u32 addr = priv->base_addr + offs;
> > +
> > +	switch (datalen) {
> > +	case 1:
> > +		*(data) = inb(addr);
> > +		break;
> > +	case 2:
> > +		*((u16 *)data) = inw(addr);
> > +		break;
> > +	case 3:
> > +		*((u16 *)data) = inw(addr);
> > +		*(data + 2) = inb(addr + 2);
> > +		break;
> > +	case 4:
> > +		*((u32 *)data) = inl(addr);
> > +		break;
> > +	default:
> > +		mlxcpld_i2c_lpc_read_buf(data, datalen, addr);
> > +		break;
> > +	}
> > +}
> > +
> > +static void mlxcpld_i2c_write_comm(struct mlxcpld_i2c_priv *priv, u8 offs,
> > +				   u8 *data, u8 datalen)
> > +{
> > +	u32 addr = priv->base_addr + offs;
> > +
> > +	switch (datalen) {
> > +	case 1:
> > +		outb(*(data), addr);
> > +		break;
> > +	case 2:
> > +		outw(*((u16 *)data), addr);
> > +		break;
> > +	case 3:
> > +		outw(*((u16 *)data), addr);
> > +		outb(*(data + 2), addr + 2);
> > +		break;
> > +	case 4:
> > +		outl(*((u32 *)data), addr);
> > +		break;
> > +	default:
> > +		mlxcpld_i2c_lpc_write_buf(data, datalen, addr);
> > +		break;
> > +	}
> > +}
> > +
> > +/* Check validity of current i2c message and all transfer.
> > + * Calculate also coomon length of all i2c messages in transfer.
> > + */
> > +static int mlxcpld_i2c_invalid_len(struct mlxcpld_i2c_priv *priv,
> > +				   const struct i2c_msg *msg, u8 *comm_len) {
> > +	u8 max_len = msg->flags == I2C_M_RD ? priv->block_sz -
> > +		     MLXCPLD_I2C_MAX_ADDR_LEN : priv->block_sz;
> > +
> > +	if (msg->len < 0 || msg->len > max_len)
> > +		return -EINVAL;
> > +
> > +	*comm_len += msg->len;
> > +	if (*comm_len > priv->block_sz)
> > +		return -EINVAL;
> > +	else
> > +		return 0;
> 
> Just 'return 0;' without else and indentation.
> 
> > +}
> > +
> > +/* Check validity of received i2c messages parameters.
> > + *  Returns 0 if OK, other - in case of invalid parameters
> > + *  or common length of data that should be passed to CPLD  */ static
> > +int mlxcpld_i2c_check_msg_params(struct mlxcpld_i2c_priv *priv,
> > +					struct i2c_msg *msgs, int num,
> > +					u8 *comm_len)
> > +{
> > +	int i;
> > +
> > +	if (!num) {
> > +		dev_err(&priv->pdev->dev, "Incorrect 0 num of messages\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	if (unlikely(msgs[0].addr > 0x7f)) {
> > +		dev_err(&priv->pdev->dev, "Invalid address 0x%03x\n",
> > +			msgs[0].addr);
> > +		return -EINVAL;
> > +	}
> > +
> > +	for (i = 0; i < num; ++i) {
> > +		if (unlikely(!msgs[i].buf)) {
> > +			dev_err(&priv->pdev->dev, "Invalid buf in msg[%d]\n",
> > +				i);
> > +			return -EINVAL;
> > +		}
> > +		if (unlikely(msgs[0].addr != msgs[i].addr)) {
> > +			dev_err(&priv->pdev->dev, "Invalid addr in msg[%d]\n",
> > +				i);
> > +			return -EINVAL;
> > +		}
> > +		if (unlikely(mlxcpld_i2c_invalid_len(priv, &msgs[i],
> > +						     comm_len))) {
> > +			dev_err(&priv->pdev->dev, "Invalid len %d msg[%d],
> addr 0x%x, lag %u\n",
> > +				msgs[i].len, i, msgs[i].addr, msgs[i].flags);
> > +			return -EINVAL;
> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +/* Check if transfer is completed and status of operation.
> > + * Returns 0 - transfer completed (both ACK or NACK),
> > + * negative - transfer isn't finished.
> > + */
> > +static int mlxcpld_i2c_check_status(struct mlxcpld_i2c_priv *priv,
> > +int *status) {
> > +	u8 val;
> > +
> > +	mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_STATUS_REG, &val, 1);
> > +
> > +	if (val & MLXCPLD_LPCI2C_TRANS_END) {
> > +		if (val & MLXCPLD_LPCI2C_STATUS_NACK)
> > +			/* The slave is unable to accept the data. No such
> > +			 * slave, command not understood, or unable to accept
> > +			 * any more data.
> > +			 */
> > +			*status = MLXCPLD_LPCI2C_NACK_IND;
> > +		else
> > +			*status = MLXCPLD_LPCI2C_ACK_IND;
> > +		return 0;
> > +	}
> > +	*status = MLXCPLD_LPCI2C_NO_IND;
> > +
> > +	return -EIO;
> > +}
> > +
> > +static void mlxcpld_i2c_set_transf_data(struct mlxcpld_i2c_priv *priv,
> > +					struct i2c_msg *msgs, int num,
> > +					u8 comm_len)
> > +{
> > +	priv->xfer.msg = msgs;
> > +	priv->xfer.msg_num = num;
> > +
> > +	/*
> > +	 * All upper layers currently are never use transfer with more than
> > +	 * 2 messages. Actually, it's also not so relevant in Mellanox systems
> > +	 * because of HW limitation. Max size of transfer is o more than 20B
> > +	 * in current x86 LPCI2C bridge.
> > +	 */
> > +	priv->xfer.cmd = (msgs[num - 1].flags & I2C_M_RD);
> > +
> > +	if (priv->xfer.cmd == I2C_M_RD) {
> > +		if (comm_len == msgs[0].len) {
> > +			/* Special case of addr_width = 0 */
> > +			priv->xfer.addr_width = 0;
> > +			priv->xfer.data_len = comm_len;
> > +		} else {
> > +			priv->xfer.addr_width = msgs[0].len;
> > +			priv->xfer.data_len = comm_len - priv-
> >xfer.addr_width;
> > +		}
> > +	} else {
> > +		/* Width (I2C_NUM_ADDR reg) isn't used in write command. */
> > +		priv->xfer.addr_width = 0;
> > +		priv->xfer.data_len = comm_len;
> > +	}
> 
> 	if (priv->xfer.cmd == I2C_M_RD && comm_len != msgs[0].len) {
> 		priv->xfer.addr_width = msgs[0].len;
> 		priv->xfer.data_len = comm_len - priv->xfer.addr_width;
> 	} else {
> 		priv->xfer.addr_width = 0;
> 		priv->xfer.data_len = comm_len;
> 	}
> 
> 7 lines vs. 12 lines.
> 
> > +}
> > +
> > +/* Reset CPLD LPCI2C block */
> > +static void mlxcpld_i2c_reset(struct mlxcpld_i2c_priv *priv) {
> > +	u8 val;
> > +
> > +	mutex_lock(&priv->lock);
> > +	mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_CTRL_REG, &val, 1);
> > +	val &= ~MLXCPLD_LPCI2C_RST_SEL_MASK;
> > +	mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_CTRL_REG, &val, 1);
> > +	mutex_unlock(&priv->lock);
> 
> I would recomment to insert empty lines after mutex_lock() and before
> mutex_unlock().
> 
> > +}
> > +
> > +/* Make sure the CPLD is ready to start transmitting.
> > + * Return 0 if it is, -EBUSY if it is not.
> > + */
> > +static int mlxcpld_i2c_check_busy(struct mlxcpld_i2c_priv *priv) {
> > +	u8 val;
> > +
> > +	mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_STATUS_REG, &val, 1);
> > +
> > +	if (val & MLXCPLD_LPCI2C_TRANS_END)
> > +		return 0;
> > +
> > +	return -EIO;
> > +}
> > +
> > +static int mlxcpld_i2c_wait_for_free(struct mlxcpld_i2c_priv *priv) {
> > +	int timeout = 0;
> > +
> > +	do {
> > +		if (!mlxcpld_i2c_check_busy(priv))
> > +			break;
> > +		usleep_range(priv->poll_time/2, priv->poll_time);
> 
> checkpatch complains:
> 
> CHECK: spaces preferred around that '/' (ctx:VxV)
> #375: FILE: drivers/i2c/busses/i2c-mlxcpld.c:375:
> +		usleep_range(priv->poll_time/2, priv->poll_time);
>  		                            ^
> 
> > +		timeout += priv->poll_time;
> > +	} while (timeout < priv->xfer_to);
> > +
> > +	if (timeout > priv->xfer_to)
> 
> Corner case (timeout == priv->xfer_to) is missed here.
> 
> if (timeout >= priv->xfer_to)
> 
> > +		return -ETIMEDOUT;
> > +
> > +	return 0;
> > +}
> > +
> > +/*
> > + * Wait for master transfer to complete.
> > + * It puts current process to sleep until we get interrupt or timeout expires.
> > + * Returns the number of transferred or read bytes or error (<0).
> > + */
> > +static int mlxcpld_i2c_wait_for_tc(struct mlxcpld_i2c_priv *priv) {
> > +	int status, i = 1, timeout = 0;
> > +	u8 datalen;
> > +	int err = 0;
> 
> Just "int err;"
> 
> See "The Power of Undefined Values" https://rusty.ozlabs.org/?p=232
> 
> > +
> > +	do {
> > +		usleep_range(priv->poll_time / 2, priv->poll_time);
> > +		if (!mlxcpld_i2c_check_status(priv, &status))
> > +			break;
> > +		timeout += priv->poll_time;
> > +	} while (status == 0 && timeout < priv->xfer_to);
> > +
> > +	switch (status) {
> > +	case MLXCPLD_LPCI2C_NO_IND:
> > +		return -ETIMEDOUT;
> 
> Please insert an empty line here to improve readability.
> 
> > +	case MLXCPLD_LPCI2C_ACK_IND:
> > +		if (priv->xfer.cmd == I2C_M_RD) {
> > +			/*
> > +			 * Actual read data len will be always the same as
> > +			 * requested len. 0xff (line pull-up) will be returned
> > +			 * if slave has no data to return. Thus don't read
> > +			 * MLXCPLD_LPCI2C_NUM_DAT_REG reg from CPLD.
> > +			 */
> > +			err = datalen = priv->xfer.data_len;
> 
> checkpatch complains:
> 
> CHECK: multiple assignments should be avoided
> #414: FILE: drivers/i2c/busses/i2c-mlxcpld.c:414:
> +			err = datalen = priv->xfer.data_len;
> 
> > +			if (priv->xfer.msg_num == 1)
> > +				i = 0;
> > +
> > +			if (!priv->xfer.msg[i].buf)
> > +				err = -EINVAL;
> > +			else
> > +				mlxcpld_i2c_read_comm(priv,
> > +
> MLXCPLD_LPCI2C_DATA_REG,
> > +						      priv->xfer.msg[i].buf,
> > +						      datalen);
> > +		} else {
> > +			err = priv->xfer.addr_width + priv->xfer.data_len;
> > +		}
> 
> Please try to avoid unnecessary indendation of big code chunks.
> 
> For example here you may consider to rewrite it as:
> 
> 	if (priv->xfer.cmd != I2C_M_RD)
> 		return (priv->xfer.addr_width + priv->xfer.data_len);
> 
> 	if (priv->xfer.msg_num == 1)
> 		i = 0;
> 	else
> 		i = 1;
> 
> 	if (!priv->xfer.msg[i].buf)
> 		return -EINVAL;
> 
> 	datalen = priv->xfer.data_len;
> 
> 	mlxcpld_i2c_read_comm(priv, MLXCPLD_LPCI2C_DATA_REG,
> 			      priv->xfer.msg[i].buf, datalen);
> 
> 	return datalen;
> 
> > +		break;
> > +	case MLXCPLD_LPCI2C_NACK_IND:
> > +		err = -EAGAIN;
> > +		break;
> > +	case MLXCPLD_LPCI2C_ERR_IND:
> > +		err = -EIO;
> > +		break;
> 
> This is dead code, from mlxcpld_i2c_check_status() function the 'status'
> variable can not be set to MLXCPLD_LPCI2C_ERR_IND.
> 
> > +	default:
> > +		break;
> > +	}
> > +
> > +	return err;
> > +}
> > +
> > +static void mlxcpld_i2c_xfer_msg(struct mlxcpld_i2c_priv *priv) {
> > +	int i, len = 0;
> > +	u8 cmd;
> > +
> > +	mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_NUM_DAT_REG,
> > +			       &priv->xfer.data_len, 1);
> > +	mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_NUM_ADDR_REG,
> > +			       &priv->xfer.addr_width, 1);
> > +
> > +	for (i = 0; i < priv->xfer.msg_num; i++) {
> > +		if ((priv->xfer.msg[i].flags & I2C_M_RD) != I2C_M_RD) {
> > +			/* Don't write to CPLD buffer in read transaction */
> > +			mlxcpld_i2c_write_comm(priv,
> MLXCPLD_LPCI2C_DATA_REG +
> > +					       len, priv->xfer.msg[i].buf,
> > +					       priv->xfer.msg[i].len);
> > +			len += priv->xfer.msg[i].len;
> > +		}
> > +	}
> > +
> > +	/* Set target slave address with command for master transfer.
> > +	 * It should be latest executed function before CPLD transaction.
> > +	 */
> > +	cmd = (priv->xfer.msg[0].addr << 1) | priv->xfer.cmd;
> > +	mlxcpld_i2c_write_comm(priv, MLXCPLD_LPCI2C_CMD_REG, &cmd, 1);
> }
> > +
> > +/* Generic lpc-i2c transfer.
> > + * Returns the number of processed messages or error (<0).
> > + */
> > +static int mlxcpld_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
> > +			    int num)
> > +{
> > +	struct mlxcpld_i2c_priv *priv = i2c_get_adapdata(adap);
> > +	u8 comm_len = 0;
> > +	int err;
> > +
> > +	err = mlxcpld_i2c_check_msg_params(priv, msgs, num, &comm_len);
> > +	if (err) {
> > +		dev_err(&priv->pdev->dev, "Incorrect message\n");
> > +		return err;
> > +	}
> > +
> > +	/* Check bus state */
> > +	if (mlxcpld_i2c_wait_for_free(priv)) {
> > +		dev_err(&priv->pdev->dev, "LPCI2C bridge is busy\n");
> > +
> > +		/*
> > +		 * Usually it means something serious has happened.
> > +		 * We can not have unfinished previous transfer
> > +		 * so it doesn't make any sense to try to stop it.
> > +		 * Probably we were not able to recover from the
> > +		 * previous error.
> > +		 * The only reasonable thing - is soft reset.
> > +		 */
> > +		mlxcpld_i2c_reset(priv);
> > +		if (mlxcpld_i2c_check_busy(priv)) {
> > +			dev_err(&priv->pdev->dev, "LPCI2C bridge is busy after
> reset\n");
> > +			return -EIO;
> > +		}
> > +	}
> > +
> > +	mlxcpld_i2c_set_transf_data(priv, msgs, num, comm_len);
> > +
> > +	mutex_lock(&priv->lock);
> 
> Please consider to insert an empty line here for readability.
> 
> > +	/* Do real transfer. Can't fail */
> > +	mlxcpld_i2c_xfer_msg(priv);
> 
> Please consider to insert an empty line here for readability.
> 
> > +	/* Wait for transaction complete */
> > +	err = mlxcpld_i2c_wait_for_tc(priv);
> 
> Please consider to insert an empty line here for readability.
> 
> > +	mutex_unlock(&priv->lock);
> > +
> > +	return err < 0 ? err : num;
> > +}
> > +
> > +static u32 mlxcpld_i2c_func(struct i2c_adapter *adap) {
> > +	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
> > +I2C_FUNC_SMBUS_BLOCK_DATA; }
> > +
> > +static const struct i2c_algorithm mlxcpld_i2c_algo = {
> > +	.master_xfer	= mlxcpld_i2c_xfer,
> > +	.functionality	= mlxcpld_i2c_func
> > +};
> > +
> > +static struct i2c_adapter mlxcpld_i2c_adapter = {
> > +	.owner          = THIS_MODULE,
> > +	.name           = "i2c-mlxcpld",
> > +	.class          = I2C_CLASS_HWMON | I2C_CLASS_SPD,
> > +	.algo           = &mlxcpld_i2c_algo,
> > +};
> > +
> > +static int mlxcpld_i2c_probe(struct platform_device *pdev) {
> > +	struct mlxcpld_i2c_priv *priv;
> > +	int err;
> > +
> > +	priv = devm_kzalloc(&pdev->dev, sizeof(struct mlxcpld_i2c_priv),
> > +			    GFP_KERNEL);
> > +	if (!priv)
> > +		return -ENOMEM;
> > +
> > +	mutex_init(&priv->lock);
> > +	platform_set_drvdata(pdev, priv);
> 
> Please insert an empty line here for readability.
> 
> > +	priv->pdev = pdev;
> 
> You store "pdev" in private data only to get &pdev->dev in runtime.
> Please store the pointer to that 'struct device' instead of pdev.
> 
> > +	priv->xfer_to = MLXCPLD_I2C_XFER_TO;
> > +	priv->retr_num = MLXCPLD_I2C_RETR_NUM;
> > +	priv->block_sz = MLXCPLD_I2C_DATA_REG_SZ;
> > +	priv->poll_time = MLXCPLD_I2C_POLL_TIME;
> 
> Why do you set all these constant values in runtime?
> Please consider to replace all of them in the code by the correspondent macros.
> 
> And also please insert an empty line here for readability.
> 
> > +	/* Register with i2c layer */
> > +	priv->adap = mlxcpld_i2c_adapter;
> > +	priv->adap.dev.parent = &pdev->dev;
> > +	i2c_set_adapdata(&priv->adap, priv);
> > +	priv->adap.retries = priv->retr_num;
> 
> priv->adap.retries = MLXCPLD_I2C_RETR_NUM;
> 
> > +	priv->adap.nr = MLXCPLD_I2C_BUS_NUM;
> > +	priv->adap.timeout = usecs_to_jiffies(priv->xfer_to);
> > +
> > +	err = i2c_add_numbered_adapter(&priv->adap);
> 
> Why do you use i2c_add_numbered_adapter() instead of i2c_add_adapter() ?

Here it is set to 1. On our systems we used to have i2c0 for Intel i801, and i2c1 for our CPLD LPC/I2C logic. 

After all I I want to enforce adapter id to pdev->id.
I already submitted code in module mlx-paltform.c  for next, which will set this id and will probe this driver. Since all this code new and going to different branches it is not so trivial to sync different modules. 

> 
> > +	if (err) {
> > +		dev_err(&pdev->dev, "Failed to add %s adapter (%d)\n",
> > +			MLXCPLD_I2C_DEVICE_NAME, err);
> > +		goto fail_adapter;
> > +	}
> > +
> > +	priv->base_addr = MLXPLAT_CPLD_LPC_I2C_BASE_ADRR;
> 
> Consider to move this assignment up to the rest of them.
> 
> > +	return 0;
> > +
> > +fail_adapter:
> > +	mutex_destroy(&priv->lock);
> > +	return err;
> > +}
> > +
> > +static int mlxcpld_i2c_remove(struct platform_device *pdev) {
> > +	struct mlxcpld_i2c_priv *priv = platform_get_drvdata(pdev);
> > +
> > +	i2c_del_adapter(&priv->adap);
> > +	mutex_destroy(&priv->lock);
> > +
> > +	return 0;
> > +}
> > +
> > +static struct platform_driver mlxcpld_i2c_driver = {
> > +	.probe		= mlxcpld_i2c_probe,
> > +	.remove		= mlxcpld_i2c_remove,
> > +	.driver = {
> > +		.name = MLXCPLD_I2C_DEVICE_NAME,
> > +	},
> > +};
> > +
> > +module_platform_driver(mlxcpld_i2c_driver);
> > +
> > +MODULE_AUTHOR("Michael Shych (michaels@...lanox.com)");
> 
> Consider to enclose email into <>, see RFC822.
> 
> > +MODULE_DESCRIPTION("Mellanox I2C-CPLD controller driver");
> > +MODULE_LICENSE("GPL v2");
> 
> MODULE_LICENSE("Dual BSD/GPL");
> 
> Correct?
> 
> > +MODULE_ALIAS("platform:i2c-mlxcpld");
> >
> 
> --
> With best wishes,
> Vladimir

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