Date:   Thu, 21 Jun 2018 23:33:21 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Piotr Bugalski <bugalski.piotr@...il.com>
Cc:     Mark Brown <broonie@...nel.org>, linux-spi@...r.kernel.org,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        Richard Weinberger <richard@....at>,
        linux-mtd@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Cyrille Pitchen <cyrille.pitchen@...rochip.com>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Piotr Bugalski <pbu@...ptera.com>
Subject: Re: [RFC PATCH 1/2] spi: Add QuadSPI driver for Atmel SAMA5D2

Hi Piotr,

On Mon, 18 Jun 2018 18:21:23 +0200
Piotr Bugalski <bugalski.piotr@...il.com> wrote:

> Kernel contains QSPI driver strongly tied to MTD and nor-flash memory.
> New spi-mem interface allows usage also other memory types, especially
> much larger NAND with SPI interface. This driver works as SPI controller
> and is not related to MTD, however can work with NAND-flash or other
> peripherals using spi-mem interface.

Thanks for working on that.

> 
> Suggested-by: Boris Brezillon <boris.brezillon@...tlin.com>
> Signed-off-by: Piotr Bugalski <pbu@...ptera.com>
> 
> ---
>  drivers/spi/Kconfig          |   9 +
>  drivers/spi/Makefile         |   1 +
>  drivers/spi/spi-atmel-qspi.c | 480 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 490 insertions(+)
>  create mode 100644 drivers/spi/spi-atmel-qspi.c
> 
> diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
> index 4a77cfa3213d..4f70a7005997 100644
> --- a/drivers/spi/Kconfig
> +++ b/drivers/spi/Kconfig
> @@ -84,6 +84,15 @@ config SPI_ATMEL
>  	  This selects a driver for the Atmel SPI Controller, present on
>  	  many AT91 ARM chips.
>  
> +config SPI_ATMEL_QSPI
> +	tristate "Atmel QuadSPI Controller"
> +	depends on ARCH_AT91 || (ARM && COMPILE_TEST)
> +	depends on OF && HAS_IOMEM
> +	help
> +	  This selects a driver for the Atmel QSPI Controller on SAMA5D2.
> +	  This controller does not support generic SPI, it supports only
> +	  spi-mem interface.
> +
>  config SPI_AU1550
>  	tristate "Au1550/Au1200/Au1300 SPI Controller"
>  	depends on MIPS_ALCHEMY
> diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
> index fe54d787cf4d..6245a5693b16 100644
> --- a/drivers/spi/Makefile
> +++ b/drivers/spi/Makefile
> @@ -16,6 +16,7 @@ obj-$(CONFIG_SPI_LOOPBACK_TEST)		+= spi-loopback-test.o
>  obj-$(CONFIG_SPI_ALTERA)		+= spi-altera.o
>  obj-$(CONFIG_SPI_ARMADA_3700)		+= spi-armada-3700.o
>  obj-$(CONFIG_SPI_ATMEL)			+= spi-atmel.o
> +obj-$(CONFIG_SPI_ATMEL_QSPI)    += spi-atmel-qspi.o
>  obj-$(CONFIG_SPI_ATH79)			+= spi-ath79.o
>  obj-$(CONFIG_SPI_AU1550)		+= spi-au1550.o
>  obj-$(CONFIG_SPI_AXI_SPI_ENGINE)	+= spi-axi-spi-engine.o
> diff --git a/drivers/spi/spi-atmel-qspi.c b/drivers/spi/spi-atmel-qspi.c
> new file mode 100644
> index 000000000000..1ee626201b0d
> --- /dev/null
> +++ b/drivers/spi/spi-atmel-qspi.c
> @@ -0,0 +1,480 @@

SPDX header here please:

// SPDX-License-Identifier: GPL-2.0

> +/*
> + * Atmel SAMA5D2 QuadSPI driver.
> + *
> + * Copyright (C) 2018 Cryptera A/S

A non-negligible portion of this code has been copied from the existing
driver. Please keep the existing copyright (you can still add Cryptera's
one).

> + * All Rights Reserved
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 (GPL v2)
> + * as published by the Free Software Foundation.
> + *
> + * 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.

Drop the license text. The SPDX header is here to replace it.

> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/of_device.h>
> +#include <linux/clk.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/spi/spi-mem.h>
> +#include <linux/delay.h>
> +
> +#define QSPI_CR         0x0000
> +#define QSPI_MR         0x0004
> +#define QSPI_RDR        0x0008
> +#define QSPI_TDR        0x000c
> +#define QSPI_SR         0x0010
> +#define QSPI_IER        0x0014
> +#define QSPI_IDR        0x0018
> +#define QSPI_IMR        0x001c
> +#define QSPI_SCR        0x0020
> +
> +#define QSPI_IAR        0x0030
> +#define QSPI_ICR        0x0034
> +#define QSPI_IFR        0x0038
> +
> +#define QSPI_WPMR       0x00e4
> +#define QSPI_WPSR       0x00e8
> +
> +/* Bitfields in QSPI_CR (Control Register) */

I personally prefer when reg offsets are declared next to the reg fields.

> +#define QSPI_CR_QSPIEN                  BIT(0)
> +#define QSPI_CR_QSPIDIS                 BIT(1)
> +#define QSPI_CR_SWRST                   BIT(7)
> +#define QSPI_CR_LASTXFER                BIT(24)
> +
> +/* Bitfields in QSPI_ICR (Instruction Code Register) */
> +#define QSPI_ICR_INST_MASK              GENMASK(7, 0)
> +#define QSPI_ICR_INST(inst)             (((inst) << 0) & QSPI_ICR_INST_MASK)
> +#define QSPI_ICR_OPT_MASK               GENMASK(23, 16)
> +#define QSPI_ICR_OPT(opt)               (((opt) << 16) & QSPI_ICR_OPT_MASK)
> +
> +/* Bitfields in QSPI_MR (Mode Register) */
> +#define QSPI_MR_SMM                     BIT(0)
> +#define QSPI_MR_LLB                     BIT(1)
> +#define QSPI_MR_WDRBT                   BIT(2)
> +#define QSPI_MR_SMRM                    BIT(3)
> +#define QSPI_MR_CSMODE_MASK             GENMASK(5, 4)
> +#define QSPI_MR_CSMODE_NOT_RELOADED     (0 << 4)
> +#define QSPI_MR_CSMODE_LASTXFER         (1 << 4)
> +#define QSPI_MR_CSMODE_SYSTEMATICALLY   (2 << 4)
> +#define QSPI_MR_NBBITS_MASK             GENMASK(11, 8)
> +#define QSPI_MR_NBBITS(n)               ((((n) - 8) << 8) & QSPI_MR_NBBITS_MASK)
> +#define QSPI_MR_DLYBCT_MASK             GENMASK(23, 16)
> +#define QSPI_MR_DLYBCT(n)               (((n) << 16) & QSPI_MR_DLYBCT_MASK)
> +#define QSPI_MR_DLYCS_MASK              GENMASK(31, 24)
> +#define QSPI_MR_DLYCS(n)                (((n) << 24) & QSPI_MR_DLYCS_MASK)
> +
> +/* Bitfields in QSPI_IFR (Instruction Frame Register) */
> +#define QSPI_IFR_WIDTH_MASK             GENMASK(2, 0)
> +#define QSPI_IFR_WIDTH_SINGLE_BIT_SPI   (0 << 0)
> +#define QSPI_IFR_WIDTH_DUAL_OUTPUT      (1 << 0)
> +#define QSPI_IFR_WIDTH_QUAD_OUTPUT      (2 << 0)
> +#define QSPI_IFR_WIDTH_DUAL_IO          (3 << 0)
> +#define QSPI_IFR_WIDTH_QUAD_IO          (4 << 0)
> +#define QSPI_IFR_WIDTH_DUAL_CMD         (5 << 0)
> +#define QSPI_IFR_WIDTH_QUAD_CMD         (6 << 0)
> +#define QSPI_IFR_INSTEN                 BIT(4)
> +#define QSPI_IFR_ADDREN                 BIT(5)
> +#define QSPI_IFR_OPTEN                  BIT(6)
> +#define QSPI_IFR_DATAEN                 BIT(7)
> +#define QSPI_IFR_OPTL_MASK              GENMASK(9, 8)
> +#define QSPI_IFR_OPTL_1BIT              (0 << 8)
> +#define QSPI_IFR_OPTL_2BIT              (1 << 8)
> +#define QSPI_IFR_OPTL_4BIT              (2 << 8)
> +#define QSPI_IFR_OPTL_8BIT              (3 << 8)
> +#define QSPI_IFR_ADDRL                  BIT(10)
> +#define QSPI_IFR_TFRTYP_MASK            GENMASK(13, 12)
> +#define QSPI_IFR_TFRTYP_TRSFR_READ      (0 << 12)
> +#define QSPI_IFR_TFRTYP_TRSFR_READ_MEM  (1 << 12)
> +#define QSPI_IFR_TFRTYP_TRSFR_WRITE     (2 << 12)
> +#define QSPI_IFR_TFRTYP_TRSFR_WRITE_MEM (3 << 13)
> +#define QSPI_IFR_CRM                    BIT(14)
> +#define QSPI_IFR_NBDUM_MASK             GENMASK(20, 16)
> +#define QSPI_IFR_NBDUM(n)               (((n) << 16) & QSPI_IFR_NBDUM_MASK)
> +
> +/* Bitfields in QSPI_SR/QSPI_IER/QSPI_IDR/QSPI_IMR  */
> +#define QSPI_SR_RDRF                    BIT(0)
> +#define QSPI_SR_TDRE                    BIT(1)
> +#define QSPI_SR_TXEMPTY                 BIT(2)
> +#define QSPI_SR_OVRES                   BIT(3)
> +#define QSPI_SR_CSR                     BIT(8)
> +#define QSPI_SR_CSS                     BIT(9)
> +#define QSPI_SR_INSTRE                  BIT(10)
> +#define QSPI_SR_QSPIENS                 BIT(24)
> +
> +#define QSPI_SR_CMD_COMPLETED           (QSPI_SR_INSTRE | QSPI_SR_CSR)

Do you really to wait for both INSTRE and CSR to consider the command
as complete?

> +
> +

Drop a blank line here.

> +/* Bitfields in QSPI_SCR (Serial Clock Register) */
> +#define QSPI_SCR_CPOL                   BIT(0)
> +#define QSPI_SCR_CPHA                   BIT(1)
> +#define QSPI_SCR_SCBR_MASK              GENMASK(15, 8)
> +#define QSPI_SCR_SCBR(n)                (((n) << 8) & QSPI_SCR_SCBR_MASK)
> +#define QSPI_SCR_DLYBS_MASK             GENMASK(23, 16)
> +#define QSPI_SCR_DLYBS(n)               (((n) << 16) & QSPI_SCR_DLYBS_MASK)
> +
> +#define QSPI_WPMR_WPKEY_PASSWD          (0x515350u << 8)
> +
> +struct atmel_qspi {
> +	struct platform_device *pdev;
> +	void __iomem *iobase;
> +	void __iomem *ahb_addr;
> +	int irq;

This field is not used and should be killed.

> +	struct clk *clk;
> +	u32 clk_rate;

This field can be removed. The same information is already stored in
spi_device->max_speed_hz.

> +	struct completion cmd_done;
> +	u32 pending;
> +};
> +
> +struct qspi_mode {
> +	u8 cmd_buswidth;
> +	u8 addr_buswidth;
> +	u8 data_buswidth;
> +	u32 config;
> +};
> +
> +static const struct qspi_mode sama5d2_qspi_modes[] = {
> +	{ 1, 1, 1, QSPI_IFR_WIDTH_SINGLE_BIT_SPI },
> +	{ 1, 1, 2, QSPI_IFR_WIDTH_DUAL_OUTPUT },
> +	{ 1, 1, 4, QSPI_IFR_WIDTH_QUAD_OUTPUT },
> +	{ 1, 2, 2, QSPI_IFR_WIDTH_DUAL_IO },
> +	{ 1, 4, 4, QSPI_IFR_WIDTH_QUAD_IO },
> +	{ 2, 2, 2, QSPI_IFR_WIDTH_DUAL_CMD },
> +	{ 4, 4, 4, QSPI_IFR_WIDTH_QUAD_CMD },
> +};
> +
> +static inline u32 qspi_readl(struct atmel_qspi *aq, u32 reg)
> +{
> +	return readl_relaxed(aq->iobase + reg);
> +}
> +
> +static inline void qspi_writel(struct atmel_qspi *aq, u32 reg, u32 value)
> +{
> +	writel_relaxed(value, aq->iobase + reg);
> +}

Please drop those wrappers and use readl/write_relaxed() directly.

> +
> +static int atmel_qspi_init(struct atmel_qspi *aq)
> +{
> +	unsigned long rate;
> +	u32 scbr;
> +
> +	qspi_writel(aq, QSPI_WPMR, QSPI_WPMR_WPKEY_PASSWD);
> +
> +	/* software reset */
> +	qspi_writel(aq, QSPI_CR, QSPI_CR_SWRST);
> +
> +	/* set QSPI mode */
> +	qspi_writel(aq, QSPI_MR, QSPI_MR_SMM);

It's already done in ->exec_op(), I think you can remove it here.

> +
> +	rate = clk_get_rate(aq->clk);
> +	if (!rate)
> +		return -EINVAL;
> +
> +	/* set baudrate */
> +	scbr = DIV_ROUND_UP(rate, aq->clk_rate);
> +	if (scbr > 0)
> +		scbr--;

Add a blank line here.

> +	qspi_writel(aq, QSPI_SCR, QSPI_SCR_SCBR(scbr));

The baudrate setting should be done in an spi_controller->setup() hook,
and the expected rate is available in spi_device->max_speed_hz.

> +
> +	/* enable qspi controller */
> +	qspi_writel(aq, QSPI_CR, QSPI_CR_QSPIEN);
> +
> +	return 0;
> +}
> +
> +static int atmel_qspi_adjust_op_size(struct spi_mem *mem, struct spi_mem_op *op)
> +{
> +	return 0;
> +}
> +
> +static inline bool is_compatible(const struct spi_mem_op *op,
> +				 const struct qspi_mode *mode)
> +{
> +	if (op->cmd.buswidth != mode->cmd_buswidth)
> +		return false;

Add a blank line here

> +	if (op->addr.nbytes && op->addr.buswidth != mode->addr_buswidth)
> +		return false;

here

> +	if (op->data.nbytes && op->data.buswidth != mode->data_buswidth)
> +		return false;

and here.

> +	return true;
> +}
> +
> +static int find_mode(const struct spi_mem_op *op)
> +{
> +	u32 i;
> +
> +	for (i = 0; i < ARRAY_SIZE(sama5d2_qspi_modes); i++)
> +		if (is_compatible(op, &sama5d2_qspi_modes[i]))
> +			return i;
> +	return -1;

	return -ENOTSUPP;

> +}
> +
> +static bool atmel_qspi_supports_op(struct spi_mem *mem,
> +				   const struct spi_mem_op *op)
> +{
> +	if (find_mode(op) < 0)
> +		return false;
> +
> +	// special case not supported by hardware

We try to avoid using C++ style comments in the kernel. 

> +	if ((op->addr.nbytes == 2) && (op->cmd.buswidth != op->addr.buswidth) &&

You don't need those extra parenthesis around each test.

> +		(op->dummy.nbytes == 0))

Always try to align on the open-parenthesis of the if () block:

	if (op->addr.nbytes == 2 && op->cmd.buswidth != op->addr.buswidth &&
	    op->dummy.nbytes == 0)

> +		return false;
> +
> +	return true;
> +}
> +
> +static irqreturn_t atmel_qspi_interrupt(int irq, void *dev_id)
> +{
> +	struct spi_controller *ctrl = dev_id;
> +	struct atmel_qspi *aq = spi_controller_get_devdata(ctrl);
> +	u32 status, mask, pending;
> +
> +	status = qspi_readl(aq, QSPI_SR);
> +	mask = qspi_readl(aq, QSPI_IMR);
> +	pending = status & mask;
> +
> +	if (!pending)
> +		return IRQ_NONE;
> +
> +	aq->pending |= pending;
> +	if ((aq->pending & QSPI_SR_CMD_COMPLETED) == QSPI_SR_CMD_COMPLETED)
> +		complete(&aq->cmd_done);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int atmel_qspi_exec_op(struct spi_mem *mem, const struct spi_mem_op *op)
> +{
> +	struct atmel_qspi *aq = spi_controller_get_devdata(mem->spi->master);
> +	int mode;
> +	u32 addr = 0;
> +	u32 dummy_cycles = 0;
> +	u32 ifr = QSPI_IFR_INSTEN;
> +	u32 icr = QSPI_ICR_INST(op->cmd.opcode);
> +
> +	qspi_writel(aq, QSPI_MR, QSPI_MR_SMM);
> +
> +	mode = find_mode(op);
> +	if (mode < 0)
> +		return -1;

		return mode;

Add a blank line here.

> +	ifr |= sama5d2_qspi_modes[mode].config;
> +
> +	if (op->dummy.buswidth && op->dummy.nbytes)
> +		dummy_cycles = op->dummy.nbytes * 8 / op->dummy.buswidth;
> +
> +	if (op->addr.buswidth) {
> +		switch (op->addr.nbytes) {
> +		case 0:
> +			break;
> +		case 1:
> +			ifr |= QSPI_IFR_OPTEN | QSPI_IFR_OPTL_8BIT;
> +			icr |= QSPI_ICR_OPT(op->addr.val & 0xff);
> +			break;
> +		case 2:
> +			if (dummy_cycles < 8 / op->addr.buswidth) {
> +				ifr &= ~QSPI_IFR_INSTEN;
> +				addr = (op->cmd.opcode << 16) |
> +					(op->addr.val & 0xffff);
> +				ifr |= QSPI_IFR_ADDREN;
> +			} else {
> +				addr = (op->addr.val << 8) & 0xffffff;
> +				dummy_cycles -= 8 / op->addr.buswidth;
> +				ifr |= QSPI_IFR_ADDREN;
> +			}
> +			break;
> +		case 3:
> +			addr = op->addr.val & 0xffffff;
> +			ifr |= QSPI_IFR_ADDREN;
> +			break;
> +		case 4:
> +			addr = op->addr.val;
> +			ifr |= QSPI_IFR_ADDREN | QSPI_IFR_ADDRL;
> +			break;
> +		default:
> +			return -1;

			return -ENOTSUPP;

This applies to other places where you return -1, you should always use
well-known error codes.

> +		}
> +	}

Add a blank line here.

> +	ifr |= QSPI_IFR_NBDUM(dummy_cycles);

Add a blank line here.

> +	if (op->data.nbytes == 0)
> +		qspi_writel(aq, QSPI_IAR, addr);

Is this really needed? You seem to write IAR a few lines below.

> +	else
> +		ifr |= QSPI_IFR_DATAEN;
> +
> +	if ((op->data.dir == SPI_MEM_DATA_IN) && (op->data.nbytes > 0))

Drop the unneeded parenthesis.

> +		ifr |= QSPI_IFR_TFRTYP_TRSFR_READ;
> +	else
> +		ifr |= QSPI_IFR_TFRTYP_TRSFR_WRITE;

This should probably be embedded in the op->data.nbytes != 0 block:

	if (op->data.nbytes) {
		ifr |= QSPI_IFR_DATAEN;

		if (op->data.dir == SPI_MEM_DATA_IN)
			ifr |= QSPI_IFR_TFRTYP_TRSFR_READ;
		else
			ifr |= QSPI_IFR_TFRTYP_TRSFR_WRITE;
	}

> +
> +	qspi_writel(aq, QSPI_IAR, addr);
> +	qspi_writel(aq, QSPI_ICR, icr);
> +	qspi_writel(aq, QSPI_IFR, ifr);

You should probably read the _SR register before starting a new operation
to make sure all status flags have been cleared.

> +	qspi_readl(aq, QSPI_IFR);
> +
> +	if (op->data.nbytes > 0) {
> +		if (op->data.dir == SPI_MEM_DATA_IN)
> +			_memcpy_fromio(op->data.buf.in,
> +				aq->ahb_addr + addr, op->data.nbytes);
> +		else
> +			_memcpy_toio(aq->ahb_addr + addr,
> +				op->data.buf.out, op->data.nbytes);
> +
> +		qspi_writel(aq, QSPI_CR, QSPI_CR_LASTXFER);
> +	}
> +
> +	aq->pending = qspi_readl(aq, QSPI_SR) & QSPI_SR_CMD_COMPLETED;
> +	if (aq->pending == QSPI_SR_CMD_COMPLETED)
> +		return 0;

Add a blank line here.

> +	reinit_completion(&aq->cmd_done);
> +	qspi_writel(aq, QSPI_IER, QSPI_SR_CMD_COMPLETED);
> +	wait_for_completion(&aq->cmd_done);

You should use wait_for_completion_timeout() to avoid stalling the system
when the event you're waiting for never happens.

> +	qspi_writel(aq, QSPI_IDR, QSPI_SR_CMD_COMPLETED);
> +
> +	return 0;
> +}
> +
> +static const struct spi_controller_mem_ops atmel_qspi_mem_ops = {
> +	.adjust_op_size = atmel_qspi_adjust_op_size,
> +	.supports_op = atmel_qspi_supports_op,
> +	.exec_op = atmel_qspi_exec_op
> +};
> +
> +static int atmel_qspi_probe(struct platform_device *pdev)
> +{
> +	struct spi_controller *ctrl;
> +	struct atmel_qspi *aq;
> +	struct device_node *np = pdev->dev.of_node;
> +	struct device_node *child;
> +	struct resource *res;
> +	int irq, err = 0;
> +
> +	ctrl = spi_alloc_master(&pdev->dev, sizeof(*aq));
> +	if (!ctrl)
> +		return -ENOMEM;
> +
> +	ctrl->mode_bits = SPI_RX_DUAL | SPI_RX_QUAD | SPI_TX_DUAL | SPI_TX_QUAD;
> +	ctrl->bus_num = -1;
> +	ctrl->mem_ops = &atmel_qspi_mem_ops;
> +	ctrl->num_chipselect = 1;
> +	ctrl->dev.of_node = pdev->dev.of_node;
> +	platform_set_drvdata(pdev, ctrl);
> +
> +	aq = spi_controller_get_devdata(ctrl);
> +
> +	if (of_get_child_count(np) != 1)
> +		return -ENODEV;

Hm, I think the core already complains if there are more children than
->num_chipselect, so I'd say this is useless. Also, you can have a
controller without any devices under, so, nchildren == 0 is a valid
case.

> +	child = of_get_next_child(np, NULL);
> +
> +	aq->pdev = pdev;
> +
> +	/* map registers */
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "qspi_base");
> +	aq->iobase = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(aq->iobase)) {
> +		dev_err(&pdev->dev, "missing registers\n");
> +		err = PTR_ERR(aq->iobase);
> +		goto err_put_ctrl;
> +	}
> +
> +	/* map AHB memory */
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "qspi_mmap");
> +	aq->ahb_addr = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(aq->ahb_addr)) {
> +		dev_err(&pdev->dev, "missing AHB memory\n");
> +		err = PTR_ERR(aq->ahb_addr);
> +		goto err_put_ctrl;
> +	}
> +
> +	/* get peripheral clock */
> +	aq->clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(aq->clk)) {
> +		dev_err(&pdev->dev, "missing peripheral clock\n");
> +		err = PTR_ERR(aq->clk);
> +		goto err_put_ctrl;
> +	}
> +
> +	err = clk_prepare_enable(aq->clk);
> +	if (err) {
> +		dev_err(&pdev->dev, "failed to enable peripheral clock\n");
> +		goto err_put_ctrl;
> +	}
> +
> +	/* request IRQ */
> +	irq = platform_get_irq(pdev, 0);
> +	if (irq < 0) {
> +		dev_err(&pdev->dev, "missing IRQ\n");
> +		err = irq;
> +		goto disable_clk;
> +	}
> +	err = devm_request_irq(&pdev->dev, irq, atmel_qspi_interrupt, 0,
> +		dev_name(&pdev->dev), ctrl);

Align dev_name() on the open-parenthesis (checkpatch --strict should
complain about that).

> +	if (err)
> +		goto disable_clk;
> +
> +	err = of_property_read_u32(child, "spi-max-frequency", &aq->clk_rate);

You should let the SPI core parse that for you (it's then stored in
spi_device->max_speed_hz and should be applied when ->setup() is called).

> +	if (err < 0)
> +		goto disable_clk;
> +
> +	init_completion(&aq->cmd_done);
> +
> +	err = atmel_qspi_init(aq);
> +	if (err)
> +		goto disable_clk;
> +
> +	of_node_put(child);
> +
> +	err = spi_register_controller(ctrl);
> +	if (err)
> +		goto disable_clk;
> +
> +	return 0;
> +
> +disable_clk:
> +	clk_disable_unprepare(aq->clk);
> +err_put_ctrl:
> +	spi_controller_put(ctrl);
> +	of_node_put(child);
> +	return err;
> +}
> +
> +static int atmel_qspi_remove(struct platform_device *pdev)
> +{
> +	struct spi_controller *ctrl = platform_get_drvdata(pdev);
> +	struct atmel_qspi *aq = spi_controller_get_devdata(ctrl);
> +
> +	qspi_writel(aq, QSPI_CR, QSPI_CR_QSPIDIS);
> +	clk_disable_unprepare(aq->clk);
> +
> +	spi_unregister_controller(ctrl);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id atmel_qspi_dt_ids[] = {
> +	{
> +		.compatible = "atmel,sama5d2-spi-qspi"
> +	},
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, atmel_qspi_dt_ids);
> +
> +static struct platform_driver atmel_qspi_driver = {
> +	.driver = {
> +		.name = "atmel_spi_qspi",

			"atmel-qspi",

> +		.of_match_table = atmel_qspi_dt_ids
> +	},
> +	.probe = atmel_qspi_probe,
> +	.remove = atmel_qspi_remove
> +};
> +
> +module_platform_driver(atmel_qspi_driver);
> +
> +
> +MODULE_DESCRIPTION("Atmel SAMA5D2 QuadSPI Driver");
> +MODULE_AUTHOR("Piotr Bugalski <pbu@...ptera.com");
> +MODULE_LICENSE("GPL v2");
> +

Drop this blank line.

Regards,

Boris

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