Message-ID: <AANLkTikobsdDp98m7SRmtzeDQxsTzgTXib-j2SQoPpdn@mail.gmail.com>
Date:	Fri, 27 Aug 2010 11:15:03 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Masayuki Ohtake <masa-korg@....okisemi.com>
Cc:	meego-dev@...go.com, LKML <linux-kernel@...r.kernel.org>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	spi-devel-general@...ts.sourceforge.net,
	"Wang, Qi" <qi.wang@...el.com>,
	"Wang, Yong Y" <yong.y.wang@...el.com>,
	andrew.chih.howe.khor@...el.com, arjan@...ux.intel.com,
	gregkh@...e.de
Subject: Re: [PATCH] Topcliff: Update PCH_SPI driver to 2.6.35

Hi Ohtake-san,

Thanks for the reply.  Some more comments below.

On Fri, Aug 27, 2010 at 7:30 AM, Masayuki Ohtake
<masa-korg@....okisemi.com> wrote:
> ----- Original Message -----
> From: "Grant Likely" <grant.likely@...retlab.ca>
> To: "Masayuki Ohtak" <masa-korg@....okisemi.com>
> Cc: <meego-dev@...go.com>; "LKML" <linux-kernel@...r.kernel.org>; "David Brownell" <dbrownell@...rs.sourceforge.net>;
> <spi-devel-general@...ts.sourceforge.net>; <qi.wang@...el.com>; <yong.y.wang@...el.com>;
> <andrew.chih.howe.khor@...el.com>; <arjan@...ux.intel.com>; <gregkh@...e.de>
> Sent: Saturday, August 14, 2010 3:49 PM
> Subject: Re: [PATCH] Topcliff: Update PCH_SPI driver to 2.6.35
>
>
>> 2010/8/10 Masayuki Ohtak <masa-korg@....okisemi.com>:
>> > SPI driver of Topcliff PCH
>> >
>> > Topcliff PCH is the platform controller hub that is going to be used in
>> > Intel's upcoming general embedded platform. All IO peripherals in
>> > Topcliff PCH are actually devices sitting on AMBA bus.
>> > Topcliff PCH has SPI I/F. Using this I/F, it is able to access system
>> > devices connected to SPI.
>> >
>> > Signed-off-by: Masayuki Ohtake <masa-korg@....okisemi.com>
>>
>> Hi Masayuki.  Thanks for the patch.  The driver is mostly structured
>> well and looks fairly good.  However, there are quite a few stylistic
>> issues that should be easy to clean up, and a few technical concerns.
>> Comments below.
>>
>> BTW, please make sure patches get sent out as plain-text, not html formatted.
>>
>> > ---
>> >  drivers/spi/Kconfig                    |   26 +
>> >  drivers/spi/Makefile                   |    4 +
>> >  drivers/spi/pch_spi.h                  |  177 +++
>> >  drivers/spi/pch_spi_main.c             | 1823
>> > ++++++++++++++++++++++++++++++++
>> >  drivers/spi/pch_spi_platform_devices.c |   56 +
>> >  5 files changed, 2086 insertions(+), 0 deletions(-)
>> >  create mode 100644 drivers/spi/pch_spi.h
>> >  create mode 100644 drivers/spi/pch_spi_main.c
>> >  create mode 100644 drivers/spi/pch_spi_platform_devices.c
>> >
>> > diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
>> > index f55eb01..b6ae72a 100644
>> > --- a/drivers/spi/Kconfig
>> > +++ b/drivers/spi/Kconfig
>> > @@ -53,6 +53,32 @@ if SPI_MASTER
>> >
>> >  comment "SPI Master Controller Drivers"
>> >
>> > +config PCH_SPI_PLATFORM_DEVICE
>> > + boolean
>> > + default y if PCH_SPI
>> > + help
>> > +   This driver is for PCH SPI of Topcliff which is an IOH for x86
>> > +   embedded processor.
>>
>> What is IOH and abbreviation for?
>>
>> > +   This registers SPI devices for a given board.
>> > +
>> > +config PCH_SPI_PLATFORM_DEVICE_COUNT
>> > + int "PCH SPI Bus count"
>> > + range 1 2
>> > + depends on PCH_SPI_PLATFORM_DEVICE
>> > + help
>> > +   This driver is for PCH SPI of Topcliff which is an IOH for x86
>> > +   embedded processor.
>> > +   The number of SPI buses/channels supported by the PCH SPI controller.
>> > +   PCH SPI of Topcliff supports only one channel.
>>
>> Being required to specific this at kernel config time isn't
>> multiplatform friendly.  Can the driver detect the number of busses at
>> runtime.
>
> How can the driver detect ?
> Could you show reference driver ?

You know the hardware better than I.  Is there a configuration or
identification register that will tell you how many spi bus instances
there are?  Regardless, then number of instances the driver can
support should not be hard coded into the kernel config.  If it is
hard coded, then the driver will not support running a single kernel
on both kinds of hardware.

>
>>
>> > +
>> > +config PCH_SPI
>> > + tristate "PCH SPI Controller"
>> > + depends on PCI
>> > + help
>> > +   This driver is for PCH SPI of Topcliff which is an IOH for x86
>> > +   embedded processor.
>> > +   This driver can access PCH SPI bus device.
>>
>> Put config PCH_SPI above PCH_SPI_PLATFORM_DEVICE and make
>> PCH_SPI_PLATFORM_DEVICE depend on PCH_SPI.  (In fact, since
>> PCH_SPI_PLATFORM_DEVICE is always yes when PCH_SPI is selected, then
>> you probably don't need two configuration signals).
>>
>> > +
>> >  config SPI_ATMEL
>> >  tristate "Atmel SPI Controller"
>> >  depends on (ARCH_AT91 || AVR32)
>> > diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
>> > index f3d2810..aecc873 100644
>> > --- a/drivers/spi/Makefile
>> > +++ b/drivers/spi/Makefile
>> > @@ -59,3 +59,7 @@ obj-$(CONFIG_SPI_TLE62X0) += tle62x0.o
>> >
>> >  # SPI slave drivers (protocol for that link)
>> >  # ... add above this line ...
>> > +obj-$(CONFIG_PCH_SPI_PLATFORM_DEVICE) += pch_spi_platform_devices.o
>> > +obj-$(CONFIG_PCH_SPI) += pch_spi.o
>> > +pch_spi-objs := pch_spi_main.o
>>
>> No need to use pch_spi-objs when there is only one .o file.  Just name
>> the .c file what you want the resulting kernel module to be named.
>> Also, please rename the modules to "spi_pch_platform_device.o" and
>> "spi_pch.o" (I'm enforcing all new spi drivers to start with the
>> prefix "spi_").
>>
>> Finally, do pch_spi_platform_devices.o and pch_spi_main.o really need
>> to be in separate modules?
>
> "spi_pch_platform_device.o" must be installed than spidev.o.
> In case,  spi_pch and spidev is integrated as module,
> it seems spidev is installed firstly.
> If you know the install order control, please how to control install ordering.

I'm not sure what you mean.  It sounds like you're talking about the
case where both this driver and spidev are compiled into the kernel
(not modules).  Am I correct?

What is the problem that you're seeing with the init order?  What is
the problem when spidev gets initialized before the driver?

Regardless, init order should not be an issue with merging
pch_spi_platform_devices and pch_spi_main into a single module.

>
>>
>> > +
>> > diff --git a/drivers/spi/pch_spi.h b/drivers/spi/pch_spi.h
>> > new file mode 100644
>> > index 0000000..b40377a
>> > --- /dev/null
>> > +++ b/drivers/spi/pch_spi.h
>> > @@ -0,0 +1,177 @@
>> > +/*
>> > + * Copyright (C) 2010 OKI SEMICONDUCTOR Co., LTD.
>> > + *
>>
>> It is helpful to have a one line description of what this file is for
>> in at the top of the header comment block.
>>
>> [...]
>> > +#define PCH_SET_BITMSK(var, bitmask) ((var) |= (bitmask))
>> > +#define PCH_CLR_BITMSK(var, bitmask) ((var) &= (~(bitmask)))
>>
>> Because the macro has side-effects, I'd prefer to see static inlines
>> used here with an all lowercase name.
>
> I understand your saying.
> But this macro uses for both setting value and returned value.
> If replacing inline function, we should make 4 functions(set/clear * void/u32)
> Thus, I want to use these macros.

which also loses any form of typechecking.  Use a static inlines
please, even if it does mean 4 functions.  Hmmm.... Actually, given
that this is just set/clear bit operation, I'd prefer to see the
macros removed entirely and the |= and &=~ written directly in the
code.

>
>>
>> > +
>> > +/**
>> > + * struct pch_spi_data - Holds the SPI channel specific details
>> > + * @io_remap_addr: The remapped PCI base address
>> > + * @p_master: Pointer to the SPI master structure
>> > + * @work: Reference to work queue handler
>> > + * @p_wk_q: Workqueue for carrying out execution of the
>> > + * requests
>> > + * @wait: Wait queue for waking up upon receiving an
>> > + * interrupt.
>> > + * @b_transfer_complete: Status of SPI Transfer
>> > + * @bcurrent_msg_processing: Status flag for message processing
>> > + * @lock: Lock for protecting this structure
>> > + * @queue: SPI Message queue
>> > + * @status: Status of the SPI driver
>> > + * @bpw_len: Length of data to be transferred in bits per
>> > + * word
>> > + * @b_transfer_active: Flag showing active transfer
>> > + * @tx_index: Transmit data count; for bookkeeping during
>> > + * transfer
>> > + * @rx_index: Receive data count; for bookkeeping during
>> > + * transfer
>> > + * @tx_buff: Buffer for data to be transmitted
>> > + * @rx_index: Buffer for Received data
>> > + * @n_curnt_chip: The chip number that this SPI driver currently
>> > + * operates on
>> > + * @p_current_chip: Reference to the current chip that this SPI
>> > + * driver currently operates on
>> > + * @p_current_msg: The current message that this SPI driver is
>> > + * handling
>> > + * @p_cur_trans: The current transfer that this SPI driver is
>> > + * handling
>> > + * @p_board_dat: Reference to the SPI device data structure
>> > + */
>> > +struct pch_spi_data {
>> > + void __iomem *io_remap_addr;
>> > + struct spi_master *p_master;
>> > + struct work_struct work;
>> > + struct workqueue_struct *p_wk_q;
>> > + wait_queue_head_t wait;
>> > + u8 b_transfer_complete;
>> > + u8 bcurrent_msg_processing;
>> > + spinlock_t lock;
>> > + struct list_head queue;
>> > + u8 status;
>> > + u32 bpw_len;
>> > + s8 b_transfer_active;
>> > + u32 tx_index;
>> > + u32 rx_index;
>> > + u16 *pkt_tx_buff;
>> > + u16 *pkt_rx_buff;
>> > + u8 n_curnt_chip;
>> > + struct spi_device *p_current_chip;
>> > + struct spi_message *p_current_msg;
>> > + struct spi_transfer *p_cur_trans;
>> > + struct pch_spi_board_data *p_board_dat;
>> > +};
>> > +
>> > +/**
>> > + * struct pch_spi_board_data - Holds the SPI device specific details
>> > + * @pdev: Pointer to the PCI device
>> > + * @irq_reg_sts: Status of IRQ registration
>> > + * @pci_req_sts: Status of pci_request_regions
>> > + * @suspend_sts: Status of suspend
>> > + * @p_data: Pointer to SPI channel data structure
>> > + */
>> > +struct pch_spi_board_data {
>> > + struct pci_dev *pdev;
>> > + u8 irq_reg_sts;
>> > + u8 pci_req_sts;
>> > + u8 suspend_sts;
>> > + struct pch_spi_data *p_data[PCH_MAX_DEV];
>> > +};
>> > +#endif
>> > diff --git a/drivers/spi/pch_spi_main.c b/drivers/spi/pch_spi_main.c
>> > new file mode 100644
>> > index 0000000..da87d92
>> > --- /dev/null
>> > +++ b/drivers/spi/pch_spi_main.c
>> > @@ -0,0 +1,1823 @@
>> > +/*
>> > + * Copyright (C) 2010 OKI SEMICONDUCTOR Co., LTD.
>> > + *
>> > + * This program is free software; you can redistribute it and/or modify
>> > + * it under the terms of the GNU General Public License as published by
>> > + * the Free Software Foundation; version 2 of the License.
>> > + *
>> > + * This program is distributed in the hope that it will be useful,
>> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> > + * GNU General Public License for more details.
>> > + *
>> > + * You should have received a copy of the GNU General Public License
>> > + * along with this program; if not, write to the Free Software
>> > + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307,
>> > USA.
>> > + */
>> > +
>> > +#include <linux/pci.h>
>> > +#include <linux/wait.h>
>> > +#include <linux/spi/spi.h>
>> > +#include <linux/interrupt.h>
>> > +#include <linux/sched.h>
>> > +#include <linux/spi/spidev.h>
>> > +#include <linux/module.h>
>> > +#include <linux/device.h>
>> > +#include <linux/mutex.h>
>> > +#include "pch_spi.h"
>> > +
>> > +static struct pci_device_id pch_spi_pcidev_id[] = {
>> > + {PCI_DEVICE(PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_GE_SPI)},
>> > + {0,}
>> > +};
>> > +
>> > +static void (*pch_spi_gcbptr) (struct pch_spi_data *);
>> > +static DEFINE_MUTEX(pch_spi_mutex);
>>
>> Are these statics really necessary?  I think the callback can be
>> removed (see my comment below).  The mutex should probably be a member
>> of the pch_spi_data structure.  Getting rid of the static symbols will
>> make it easier if the driver ever needs to support multiple instances
>> of the device.
>
> As to 'pch_spi_gcbptr', I agree with you.
>
> As to mutex, since many drivers accepted by upstream use 'static DEFINE_MUTEX',
> I think it is right to use it.

No.  Since each spi bus instance is separate without any shared data
between them, the mutex should be per-instance.  Move it into the
private data structure and initialize it in the probe routine with mutex_init().

g.
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