Message-ID: <a414ebd5-82ff-4b43-0fd8-6d1045eb2308@kontron.de>
Date:   Fri, 7 Dec 2018 09:27:11 +0000
From:   Schrempf Frieder <frieder.schrempf@...tron.de>
To:     Yogesh Narayan Gaur <yogeshnarayan.gaur@....com>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "boris.brezillon@...tlin.com" <boris.brezillon@...tlin.com>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        Marek Vasut <marek.vasut@...il.com>,
        Mark Brown <broonie@...nel.org>, Han Xu <han.xu@....com>
CC:     "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "richard@....at" <richard@....at>,
        "miquel.raynal@...tlin.com" <miquel.raynal@...tlin.com>,
        David Wolfe <david.wolfe@....com>,
        Fabio Estevam <fabio.estevam@....com>,
        "Prabhakar Kushwaha" <prabhakar.kushwaha@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 3/9] spi: Add a driver for the Freescale/NXP QuadSPI
 controller

On 07.12.18 06:46, Yogesh Narayan Gaur wrote:
> Hi Frieder,
> 
>> -----Original Message-----
>> From: Schrempf Frieder [mailto:frieder.schrempf@...tron.de]
>> Sent: Tuesday, December 4, 2018 7:45 PM
>> To: linux-mtd@...ts.infradead.org; boris.brezillon@...tlin.com; linux-
>> spi@...r.kernel.org; Marek Vasut <marek.vasut@...il.com>; Mark Brown
>> <broonie@...nel.org>; Han Xu <han.xu@....com>
>> Cc: dwmw2@...radead.org; computersforpeace@...il.com; richard@....at;
>> miquel.raynal@...tlin.com; David Wolfe <david.wolfe@....com>; Fabio
>> Estevam <fabio.estevam@....com>; Prabhakar Kushwaha
>> <prabhakar.kushwaha@....com>; Yogesh Narayan Gaur
>> <yogeshnarayan.gaur@....com>; shawnguo@...nel.org; Schrempf Frieder
>> <frieder.schrempf@...tron.de>; linux-kernel@...r.kernel.org
>> Subject: [PATCH v7 3/9] spi: Add a driver for the Freescale/NXP QuadSPI
>> controller
>>
>> From: Frieder Schrempf <frieder.schrempf@...tron.de>
>>
>> This driver is derived from the SPI NOR driver at mtd/spi-nor/fsl-quadspi.c. It
>> uses the new SPI memory interface of the SPI framework to issue flash memory
>> operations to up to four connected flash chips (2 buses with 2 CS each).
>>
>> The controller does not support generic SPI messages.
>>
>> This patch also disables the build of the "old" driver and reuses its Kconfig option
>> CONFIG_SPI_FSL_QUADSPI to replace it.
>>
>> Signed-off-by: Frieder Schrempf <frieder.schrempf@...tron.de>
>> ---
>>   drivers/mtd/spi-nor/Kconfig  |   9 -
>>   drivers/mtd/spi-nor/Makefile |   1 -
>>   drivers/spi/Kconfig          |  11 +
>>   drivers/spi/Makefile         |   1 +
>>   drivers/spi/spi-fsl-qspi.c   | 966 ++++++++++++++++++++++++++++++++++++++
>>   5 files changed, 978 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/mtd/spi-nor/Kconfig b/drivers/mtd/spi-nor/Kconfig index
>> 6cc9c92..d1ca307 100644
>> --- a/drivers/mtd/spi-nor/Kconfig
>> +++ b/drivers/mtd/spi-nor/Kconfig
>> @@ -59,15 +59,6 @@ config SPI_CADENCE_QUADSPI
>>   	  device with a Cadence QSPI controller and want to access the
>>   	  Flash as an MTD device.
>>
>> -config SPI_FSL_QUADSPI
>> -	tristate "Freescale Quad SPI controller"
>> -	depends on ARCH_MXC || SOC_LS1021A || ARCH_LAYERSCAPE ||
>> COMPILE_TEST
>> -	depends on HAS_IOMEM
>> -	help
>> -	  This enables support for the Quad SPI controller in master mode.
>> -	  This controller does not support generic SPI. It only supports
>> -	  SPI NOR.
>> -
>>   config SPI_HISI_SFC
>>   	tristate "Hisilicon SPI-NOR Flash Controller(SFC)"
>>   	depends on ARCH_HISI || COMPILE_TEST
>> diff --git a/drivers/mtd/spi-nor/Makefile b/drivers/mtd/spi-nor/Makefile index
>> f4c61d2..3f160c2e3 100644
>> --- a/drivers/mtd/spi-nor/Makefile
>> +++ b/drivers/mtd/spi-nor/Makefile
>> @@ -3,7 +3,6 @@ obj-$(CONFIG_MTD_SPI_NOR)	+= spi-nor.o
>>   obj-$(CONFIG_SPI_ASPEED_SMC)	+= aspeed-smc.o
>>   obj-$(CONFIG_SPI_ATMEL_QUADSPI)	+= atmel-quadspi.o
>>   obj-$(CONFIG_SPI_CADENCE_QUADSPI)	+= cadence-quadspi.o
>> -obj-$(CONFIG_SPI_FSL_QUADSPI)	+= fsl-quadspi.o
>>   obj-$(CONFIG_SPI_HISI_SFC)	+= hisi-sfc.o
>>   obj-$(CONFIG_MTD_MT81xx_NOR)    += mtk-quadspi.o
>>   obj-$(CONFIG_SPI_NXP_SPIFI)	+= nxp-spifi.o
>> diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig index 7d3a5c9..8c84186
>> 100644
>> --- a/drivers/spi/Kconfig
>> +++ b/drivers/spi/Kconfig
>> @@ -259,6 +259,17 @@ config SPI_FSL_LPSPI
>>   	help
>>   	  This enables Freescale i.MX LPSPI controllers in master mode.
>>
>> +config SPI_FSL_QUADSPI
>> +	tristate "Freescale QSPI controller"
>> +	depends on ARCH_MXC || SOC_LS1021A || ARCH_LAYERSCAPE ||
>> COMPILE_TEST
>> +	depends on HAS_IOMEM
>> +	help
>> +	  This enables support for the Quad SPI controller in master mode.
>> +	  Up to four flash chips can be connected on two buses with two
>> +	  chipselects each.
>> +	  This controller does not support generic SPI messages. It only
>> +	  supports the high-level SPI memory interface.
>> +
>>   config SPI_GPIO
>>   	tristate "GPIO-based bitbanging SPI Master"
>>   	depends on GPIOLIB || COMPILE_TEST
>> diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile index 3575205..5377e61
>> 100644
>> --- a/drivers/spi/Makefile
>> +++ b/drivers/spi/Makefile
>> @@ -44,6 +44,7 @@ obj-$(CONFIG_SPI_FSL_DSPI)		+= spi-fsl-
>> dspi.o
>>   obj-$(CONFIG_SPI_FSL_LIB)		+= spi-fsl-lib.o
>>   obj-$(CONFIG_SPI_FSL_ESPI)		+= spi-fsl-espi.o
>>   obj-$(CONFIG_SPI_FSL_LPSPI)		+= spi-fsl-lpspi.o
>> +obj-$(CONFIG_SPI_FSL_QUADSPI)		+= spi-fsl-qspi.o
>>   obj-$(CONFIG_SPI_FSL_SPI)		+= spi-fsl-spi.o
>>   obj-$(CONFIG_SPI_GPIO)			+= spi-gpio.o
>>   obj-$(CONFIG_SPI_IMG_SPFI)		+= spi-img-spfi.o
>> diff --git a/drivers/spi/spi-fsl-qspi.c b/drivers/spi/spi-fsl-qspi.c new file mode
>> 100644 index 0000000..f0a3400
>> --- /dev/null
>> +++ b/drivers/spi/spi-fsl-qspi.c
>> @@ -0,0 +1,966 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +
>> +/*
>> + * Freescale QuadSPI driver.
>> + *
>> + * Copyright (C) 2013 Freescale Semiconductor, Inc.
>> + * Copyright (C) 2018 Bootlin
>> + * Copyright (C) 2018 exceet electronics GmbH
>> + * Copyright (C) 2018 Kontron Electronics GmbH
>> + *
>> + * Transition to SPI MEM interface:
>> + * Authors:
>> + *     Boris Brezillion <boris.brezillon@...tlin.com>
>> + *     Frieder Schrempf <frieder.schrempf@...tron.de>
>> + *     Yogesh Gaur <yogeshnarayan.gaur@....com>
>> + *     Suresh Gupta <suresh.gupta@....com>
>> + *
>> + * Based on the original fsl-quadspi.c spi-nor driver:
>> + * Author: Freescale Semiconductor, Inc.
>> + *
>> + */
>> +
>> +#include <linux/bitops.h>
>> +#include <linux/clk.h>
>> +#include <linux/completion.h>
>> +#include <linux/delay.h>
>> +#include <linux/err.h>
>> +#include <linux/errno.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/io.h>
>> +#include <linux/iopoll.h>
>> +#include <linux/jiffies.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/mutex.h>
>> +#include <linux/of.h>
>> +#include <linux/of_device.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/pm_qos.h>
>> +#include <linux/sizes.h>
>> +
>> +#include <linux/spi/spi.h>
>> +#include <linux/spi/spi-mem.h>
>> +
>> +/*
>> + * The driver only uses one single LUT entry, that is updated on
>> + * each call of exec_op(). Index 0 is preset at boot with a basic
>> + * read operation, so let's use the last entry (15).
>> + */
>> +#define	SEQID_LUT			15
>> +
>> +/* Registers used by the driver */
>> +#define QUADSPI_MCR			0x00
>> +#define QUADSPI_MCR_RESERVED_MASK	GENMASK(19, 16)
>> +#define QUADSPI_MCR_MDIS_MASK		BIT(14)
>> +#define QUADSPI_MCR_CLR_TXF_MASK	BIT(11)
>> +#define QUADSPI_MCR_CLR_RXF_MASK	BIT(10)
>> +#define QUADSPI_MCR_DDR_EN_MASK		BIT(7)
>> +#define QUADSPI_MCR_END_CFG_MASK	GENMASK(3, 2)
>> +#define QUADSPI_MCR_SWRSTHD_MASK	BIT(1)
>> +#define QUADSPI_MCR_SWRSTSD_MASK	BIT(0)
>> +
>> +#define QUADSPI_IPCR			0x08
>> +#define QUADSPI_IPCR_SEQID(x)		((x) << 24)
>> +
>> +#define QUADSPI_BUF3CR			0x1c
>> +#define QUADSPI_BUF3CR_ALLMST_MASK	BIT(31)
>> +#define QUADSPI_BUF3CR_ADATSZ(x)	((x) << 8)
>> +#define QUADSPI_BUF3CR_ADATSZ_MASK	GENMASK(15, 8)
>> +
>> +#define QUADSPI_BFGENCR			0x20
>> +#define QUADSPI_BFGENCR_SEQID(x)	((x) << 12)
>> +
>> +#define QUADSPI_BUF0IND			0x30
>> +#define QUADSPI_BUF1IND			0x34
>> +#define QUADSPI_BUF2IND			0x38
>> +#define QUADSPI_SFAR			0x100
>> +
>> +#define QUADSPI_SMPR			0x108
>> +#define QUADSPI_SMPR_DDRSMP_MASK	GENMASK(18, 16)
>> +#define QUADSPI_SMPR_FSDLY_MASK		BIT(6)
>> +#define QUADSPI_SMPR_FSPHS_MASK		BIT(5)
>> +#define QUADSPI_SMPR_HSENA_MASK		BIT(0)
>> +
>> +#define QUADSPI_RBCT			0x110
>> +#define QUADSPI_RBCT_WMRK_MASK		GENMASK(4, 0)
>> +#define QUADSPI_RBCT_RXBRD_USEIPS	BIT(8)
>> +
>> +#define QUADSPI_TBDR			0x154
>> +
>> +#define QUADSPI_SR			0x15c
>> +#define QUADSPI_SR_IP_ACC_MASK		BIT(1)
>> +#define QUADSPI_SR_AHB_ACC_MASK		BIT(2)
>> +
>> +#define QUADSPI_FR			0x160
>> +#define QUADSPI_FR_TFF_MASK		BIT(0)
>> +
>> +#define QUADSPI_SPTRCLR			0x16c
>> +#define QUADSPI_SPTRCLR_IPPTRC		BIT(8)
>> +#define QUADSPI_SPTRCLR_BFPTRC		BIT(0)
>> +
>> +#define QUADSPI_SFA1AD			0x180
>> +#define QUADSPI_SFA2AD			0x184
>> +#define QUADSPI_SFB1AD			0x188
>> +#define QUADSPI_SFB2AD			0x18c
>> +#define QUADSPI_RBDR(x)			(0x200 + ((x) * 4))
>> +
>> +#define QUADSPI_LUTKEY			0x300
>> +#define QUADSPI_LUTKEY_VALUE		0x5AF05AF0
>> +
>> +#define QUADSPI_LCKCR			0x304
>> +#define QUADSPI_LCKER_LOCK		BIT(0)
>> +#define QUADSPI_LCKER_UNLOCK		BIT(1)
>> +
>> +#define QUADSPI_RSER			0x164
>> +#define QUADSPI_RSER_TFIE		BIT(0)
>> +
>> +#define QUADSPI_LUT_BASE		0x310
>> +#define QUADSPI_LUT_OFFSET		(SEQID_LUT * 4 * 4)
>> +#define QUADSPI_LUT_REG(idx) \
>> +	(QUADSPI_LUT_BASE + QUADSPI_LUT_OFFSET + (idx) * 4)
>> +
>> +/* Instruction set for the LUT register */
>> +#define LUT_STOP		0
>> +#define LUT_CMD			1
>> +#define LUT_ADDR		2
>> +#define LUT_DUMMY		3
>> +#define LUT_MODE		4
>> +#define LUT_MODE2		5
>> +#define LUT_MODE4		6
>> +#define LUT_FSL_READ		7
>> +#define LUT_FSL_WRITE		8
>> +#define LUT_JMP_ON_CS		9
>> +#define LUT_ADDR_DDR		10
>> +#define LUT_MODE_DDR		11
>> +#define LUT_MODE2_DDR		12
>> +#define LUT_MODE4_DDR		13
>> +#define LUT_FSL_READ_DDR	14
>> +#define LUT_FSL_WRITE_DDR	15
>> +#define LUT_DATA_LEARN		16
>> +
>> +/*
>> + * The PAD definitions for LUT register.
>> + *
>> + * The pad stands for the number of IO lines [0:3].
>> + * For example, the quad read needs four IO lines,
>> + * so you should use LUT_PAD(4).
>> + */
>> +#define LUT_PAD(x) (fls(x) - 1)
>> +
>> +/*
>> + * Macro for constructing the LUT entries with the following
>> + * register layout:
>> + *
>> + *  ---------------------------------------------------
>> + *  | INSTR1 | PAD1 | OPRND1 | INSTR0 | PAD0 | OPRND0 |
>> + *  ---------------------------------------------------
>> + */
>> +#define LUT_DEF(idx, ins, pad, opr)					\
>> +	((((ins) << 10) | ((pad) << 8) | (opr)) << (((idx) % 2) * 16))
>> +
>> +/* Controller needs driver to swap endianness */
>> +#define QUADSPI_QUIRK_SWAP_ENDIAN	BIT(0)
>> +
>> +/* Controller needs 4x internal clock */
>> +#define QUADSPI_QUIRK_4X_INT_CLK	BIT(1)
>> +
>> +/*
>> + * TKT253890, the controller needs the driver to fill the txfifo with
>> + * 16 bytes at least to trigger a data transfer, even though the extra
>> + * data won't be transferred.
>> + */
>> +#define QUADSPI_QUIRK_TKT253890		BIT(2)
>> +
>> +/* TKT245618, the controller cannot wake up from wait mode */
>> +#define QUADSPI_QUIRK_TKT245618		BIT(3)
>> +
>> +/*
>> + * Controller adds QSPI_AMBA_BASE (base address of the mapped memory)
>> + * internally. No need to add it when setting SFXXAD and SFAR registers
>> +*/
>> +#define QUADSPI_QUIRK_BASE_INTERNAL	BIT(4)
>> +
>> +struct fsl_qspi_devtype_data {
>> +	unsigned int rxfifo;
>> +	unsigned int txfifo;
>> +	unsigned int ahb_buf_size;
>> +	unsigned int quirks;
>> +	bool little_endian;
>> +};
>> +
>> +static const struct fsl_qspi_devtype_data vybrid_data = {
>> +	.rxfifo = SZ_128,
>> +	.txfifo = SZ_64,
>> +	.ahb_buf_size = SZ_1K,
>> +	.quirks = QUADSPI_QUIRK_SWAP_ENDIAN,
>> +	.little_endian = true,
>> +};
>> +
>> +static const struct fsl_qspi_devtype_data imx6sx_data = {
>> +	.rxfifo = SZ_128,
>> +	.txfifo = SZ_512,
>> +	.ahb_buf_size = SZ_1K,
>> +	.quirks = QUADSPI_QUIRK_4X_INT_CLK | QUADSPI_QUIRK_TKT245618,
>> +	.little_endian = true,
>> +};
>> +
>> +static const struct fsl_qspi_devtype_data imx7d_data = {
>> +	.rxfifo = SZ_512,
>> +	.txfifo = SZ_512,
>> +	.ahb_buf_size = SZ_1K,
>> +	.quirks = QUADSPI_QUIRK_TKT253890 | QUADSPI_QUIRK_4X_INT_CLK,
>> +	.little_endian = true,
>> +};
>> +
>> +static const struct fsl_qspi_devtype_data imx6ul_data = {
>> +	.rxfifo = SZ_128,
>> +	.txfifo = SZ_512,
>> +	.ahb_buf_size = SZ_1K,
>> +	.quirks = QUADSPI_QUIRK_TKT253890 | QUADSPI_QUIRK_4X_INT_CLK,
>> +	.little_endian = true,
>> +};
>> +
>> +static const struct fsl_qspi_devtype_data ls1021a_data = {
>> +	.rxfifo = SZ_128,
>> +	.txfifo = SZ_64,
>> +	.ahb_buf_size = SZ_1K,
>> +	.quirks = 0,
>> +	.little_endian = false,
>> +};
>> +
>> +static const struct fsl_qspi_devtype_data ls2080a_data = {
>> +	.rxfifo = SZ_128,
>> +	.txfifo = SZ_64,
>> +	.ahb_buf_size = SZ_1K,
>> +	.quirks = QUADSPI_QUIRK_TKT253890 |
>> QUADSPI_QUIRK_BASE_INTERNAL,
>> +	.little_endian = true,
>> +};
>> +
>> +struct fsl_qspi {
>> +	void __iomem *iobase;
>> +	void __iomem *ahb_addr;
>> +	u32 memmap_phy;
>> +	struct clk *clk, *clk_en;
>> +	struct device *dev;
>> +	struct completion c;
>> +	const struct fsl_qspi_devtype_data *devtype_data;
>> +	struct mutex lock;
>> +	struct pm_qos_request pm_qos_req;
>> +	int selected;
>> +};
>> +
>> +static inline int needs_swap_endian(struct fsl_qspi *q) {
>> +	return q->devtype_data->quirks & QUADSPI_QUIRK_SWAP_ENDIAN; }
>> +
>> +static inline int needs_4x_clock(struct fsl_qspi *q) {
>> +	return q->devtype_data->quirks & QUADSPI_QUIRK_4X_INT_CLK; }
>> +
>> +static inline int needs_fill_txfifo(struct fsl_qspi *q) {
>> +	return q->devtype_data->quirks & QUADSPI_QUIRK_TKT253890; }
>> +
>> +static inline int needs_wakeup_wait_mode(struct fsl_qspi *q) {
>> +	return q->devtype_data->quirks & QUADSPI_QUIRK_TKT245618; }
>> +
>> +static inline int needs_amba_base_offset(struct fsl_qspi *q) {
>> +	return !(q->devtype_data->quirks &
>> QUADSPI_QUIRK_BASE_INTERNAL); }
>> +
>> +/*
>> + * An IC bug makes it necessary to rearrange the 32-bit data.
>> + * Later chips, such as IMX6SLX, have fixed this bug.
>> + */
>> +static inline u32 fsl_qspi_endian_xchg(struct fsl_qspi *q, u32 a) {
>> +	return needs_swap_endian(q) ? __swab32(a) : a; }
>> +
>> +/*
>> + * R/W functions for big- or little-endian registers:
>> + * The QSPI controller's endianness is independent of
>> + * the CPU core's endianness. So far, although the CPU
>> + * core is little-endian the QSPI controller can use
>> + * big-endian or little-endian.
>> + */
>> +static void qspi_writel(struct fsl_qspi *q, u32 val, void __iomem
>> +*addr) {
>> +	if (q->devtype_data->little_endian)
>> +		iowrite32(val, addr);
>> +	else
>> +		iowrite32be(val, addr);
>> +}
>> +
>> +static u32 qspi_readl(struct fsl_qspi *q, void __iomem *addr) {
>> +	if (q->devtype_data->little_endian)
>> +		return ioread32(addr);
>> +
>> +	return ioread32be(addr);
>> +}
>> +
>> +static irqreturn_t fsl_qspi_irq_handler(int irq, void *dev_id) {
>> +	struct fsl_qspi *q = dev_id;
>> +	u32 reg;
>> +
>> +	/* clear interrupt */
>> +	reg = qspi_readl(q, q->iobase + QUADSPI_FR);
>> +	qspi_writel(q, reg, q->iobase + QUADSPI_FR);
>> +
>> +	if (reg & QUADSPI_FR_TFF_MASK)
>> +		complete(&q->c);
>> +
>> +	dev_dbg(q->dev, "QUADSPI_FR : 0x%.8x:0x%.8x\n", 0, reg);
>> +	return IRQ_HANDLED;
>> +}
>> +
>> +static int fsl_qspi_check_buswidth(struct fsl_qspi *q, u8 width) {
>> +	switch (width) {
>> +	case 1:
>> +	case 2:
>> +	case 4:
>> +		return 0;
>> +	}
>> +
>> +	return -ENOTSUPP;
>> +}
>> +
>> +static bool fsl_qspi_supports_op(struct spi_mem *mem,
>> +				 const struct spi_mem_op *op)
>> +{
>> +	struct fsl_qspi *q = spi_controller_get_devdata(mem->spi->master);
>> +	int ret;
>> +
>> +	ret = fsl_qspi_check_buswidth(q, op->cmd.buswidth);
>> +
>> +	if (op->addr.nbytes)
>> +		ret |= fsl_qspi_check_buswidth(q, op->addr.buswidth);
>> +
>> +	if (op->dummy.nbytes)
>> +		ret |= fsl_qspi_check_buswidth(q, op->dummy.buswidth);
>> +
>> +	if (op->data.nbytes)
>> +		ret |= fsl_qspi_check_buswidth(q, op->data.buswidth);
>> +
>> +	if (ret)
>> +		return false;
>> +
>> +	/*
>> +	 * The number of instructions needed for the op, needs
>> +	 * to fit into a single LUT entry.
>> +	 */
>> +	if (op->addr.nbytes +
>> +	   (op->dummy.nbytes ? 1:0) +
>> +	   (op->data.nbytes ? 1:0) > 6)
>> +		return false;
>> +
>> +	/* Max 64 dummy clock cycles supported */
>> +	if (op->dummy.nbytes &&
>> +	    (op->dummy.nbytes * 8 / op->dummy.buswidth > 64))
>> +		return false;
>> +
>> +	/* Max data length, check controller limits and alignment */
>> +	if (op->data.dir == SPI_MEM_DATA_IN &&
>> +	    (op->data.nbytes > q->devtype_data->ahb_buf_size ||
>> +	     (op->data.nbytes > q->devtype_data->rxfifo - 4 &&
>> +	      !IS_ALIGNED(op->data.nbytes, 8))))
>> +		return false;
>> +
>> +	if (op->data.dir == SPI_MEM_DATA_OUT &&
>> +	    op->data.nbytes > q->devtype_data->txfifo)
>> +		return false;
>> +
>> +	return true;
>> +}
>> +
>> +static void fsl_qspi_prepare_lut(struct fsl_qspi *q,
>> +				 const struct spi_mem_op *op)
>> +{
>> +	void __iomem *base = q->iobase;
>> +	u32 lutval[4] = {};
>> +	int lutidx = 1, i;
>> +
>> +	lutval[0] |= LUT_DEF(0, LUT_CMD, LUT_PAD(op->cmd.buswidth),
>> +			     op->cmd.opcode);
>> +
>> +	/*
>> +	 * For some unknown reason, using LUT_ADDR doesn't work in some
>> +	 * cases (at least with only one byte long addresses), so
>> +	 * let's use LUT_MODE to write the address bytes one by one
>> +	 */
>> +	for (i = 0; i < op->addr.nbytes; i++) {
>> +		u8 addrbyte = op->addr.val >> (8 * (op->addr.nbytes - i - 1));
>> +
>> +		lutval[lutidx / 2] |= LUT_DEF(lutidx, LUT_MODE,
>> +					      LUT_PAD(op->addr.buswidth),
>> +					      addrbyte);
>> +		lutidx++;
>> +	}
>> +
>> +	if (op->dummy.nbytes) {
>> +		lutval[lutidx / 2] |= LUT_DEF(lutidx, LUT_DUMMY,
>> +					      LUT_PAD(op->dummy.buswidth),
>> +					      op->dummy.nbytes * 8 /
>> +					      op->dummy.buswidth);
>> +		lutidx++;
>> +	}
>> +
>> +	if (op->data.nbytes) {
>> +		lutval[lutidx / 2] |= LUT_DEF(lutidx,
>> +					      op->data.dir ==
>> SPI_MEM_DATA_IN ?
>> +					      LUT_FSL_READ : LUT_FSL_WRITE,
>> +					      LUT_PAD(op->data.buswidth),
>> +					      0);
>> +		lutidx++;
>> +	}
>> +
>> +	lutval[lutidx / 2] |= LUT_DEF(lutidx, LUT_STOP, 0, 0);
>> +
>> +	/* unlock LUT */
>> +	qspi_writel(q, QUADSPI_LUTKEY_VALUE, q->iobase + QUADSPI_LUTKEY);
>> +	qspi_writel(q, QUADSPI_LCKER_UNLOCK, q->iobase + QUADSPI_LCKCR);
>> +
>> +	/* fill LUT */
>> +	for (i = 0; i < ARRAY_SIZE(lutval); i++)
>> +		qspi_writel(q, lutval[i], base + QUADSPI_LUT_REG(i));
>> +
>> +	/* lock LUT */
>> +	qspi_writel(q, QUADSPI_LUTKEY_VALUE, q->iobase + QUADSPI_LUTKEY);
>> +	qspi_writel(q, QUADSPI_LCKER_LOCK, q->iobase + QUADSPI_LCKCR); }
>> +
>> +static int fsl_qspi_clk_prep_enable(struct fsl_qspi *q) {
>> +	int ret;
>> +
>> +	ret = clk_prepare_enable(q->clk_en);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = clk_prepare_enable(q->clk);
>> +	if (ret) {
>> +		clk_disable_unprepare(q->clk_en);
>> +		return ret;
>> +	}
>> +
>> +	if (needs_wakeup_wait_mode(q))
>> +		pm_qos_add_request(&q->pm_qos_req,
>> PM_QOS_CPU_DMA_LATENCY, 0);
>> +
>> +	return 0;
>> +}
>> +
>> +static void fsl_qspi_clk_disable_unprep(struct fsl_qspi *q) {
>> +	if (needs_wakeup_wait_mode(q))
>> +		pm_qos_remove_request(&q->pm_qos_req);
>> +
>> +	clk_disable_unprepare(q->clk);
>> +	clk_disable_unprepare(q->clk_en);
>> +}
>> +
>> +/*
>> + * If we have changed the content of the flash by writing or erasing,
>> +or if we
>> + * read from flash with a different offset into the page buffer, we
>> +need to
>> + * invalidate the AHB buffer. If we do not do so, we may read out the
>> +wrong
>> + * data. The spec tells us reset the AHB domain and Serial Flash domain
>> +at
>> + * the same time.
>> + */
>> +static void fsl_qspi_invalidate(struct fsl_qspi *q) {
>> +	u32 reg;
>> +
>> +	reg = qspi_readl(q, q->iobase + QUADSPI_MCR);
>> +	reg |= QUADSPI_MCR_SWRSTHD_MASK |
>> QUADSPI_MCR_SWRSTSD_MASK;
>> +	qspi_writel(q, reg, q->iobase + QUADSPI_MCR);
>> +
>> +	/*
>> +	 * The minimum delay : 1 AHB + 2 SFCK clocks.
>> +	 * Delay 1 us is enough.
>> +	 */
>> +	udelay(1);
>> +
>> +	reg &= ~(QUADSPI_MCR_SWRSTHD_MASK |
>> QUADSPI_MCR_SWRSTSD_MASK);
>> +	qspi_writel(q, reg, q->iobase + QUADSPI_MCR); }
>> +
>> +static void fsl_qspi_select_mem(struct fsl_qspi *q, struct spi_device
>> +*spi) {
>> +	unsigned long rate = spi->max_speed_hz;
>> +	int ret;
>> +
>> +	if (q->selected == spi->chip_select)
>> +		return;
>> +
>> +	if (needs_4x_clock(q))
>> +		rate *= 4;
>> +
>> +	fsl_qspi_clk_disable_unprep(q);
>> +
>> +	ret = clk_set_rate(q->clk, rate);
>> +	if (ret)
>> +		return;
>> +
>> +	ret = fsl_qspi_clk_prep_enable(q);
>> +	if (ret)
>> +		return;
>> +
>> +	q->selected = spi->chip_select;
>> +
>> +	fsl_qspi_invalidate(q);
>> +}
>> +
>> +static void fsl_qspi_read_ahb(struct fsl_qspi *q, const struct
>> +spi_mem_op *op) {
>> +	memcpy_fromio(op->data.buf.in,
>> +		      q->ahb_addr + q->selected * q->devtype_data-
>>> ahb_buf_size,
>> +		      op->data.nbytes);
>> +}
>> +
>> +static void fsl_qspi_fill_txfifo(struct fsl_qspi *q,
>> +				 const struct spi_mem_op *op)
>> +{
>> +	void __iomem *base = q->iobase;
>> +	int i;
>> +	u32 val;
>> +
>> +	for (i = 0; i < ALIGN_DOWN(op->data.nbytes, 4); i += 4) {
>> +		memcpy(&val, op->data.buf.out + i, 4);
>> +		val = fsl_qspi_endian_xchg(q, val);
>> +		qspi_writel(q, val, base + QUADSPI_TBDR);
>> +	}
>> +
>> +	if (i < op->data.nbytes) {
>> +		memcpy(&val, op->data.buf.out + i, op->data.nbytes - i);
>> +		val = fsl_qspi_endian_xchg(q, val);
>> +		qspi_writel(q, val, base + QUADSPI_TBDR);
>> +	}
>> +
>> +	if (needs_fill_txfifo(q)) {
>> +		for (i = op->data.nbytes; i < 16; i += 4)
>> +			qspi_writel(q, 0, base + QUADSPI_TBDR);
>> +	}
>> +}
>> +
>> +static void fsl_qspi_read_rxfifo(struct fsl_qspi *q,
>> +			  const struct spi_mem_op *op)
>> +{
>> +	void __iomem *base = q->iobase;
>> +	int i;
>> +	u8 *buf = op->data.buf.in;
>> +	u32 val;
>> +
>> +	for (i = 0; i < ALIGN_DOWN(op->data.nbytes, 4); i += 4) {
>> +		val = qspi_readl(q, base + QUADSPI_RBDR(i / 4));
>> +		val = fsl_qspi_endian_xchg(q, val);
>> +		memcpy(buf + i, &val, 4);
>> +	}
>> +
>> +	if (i < op->data.nbytes) {
>> +		val = qspi_readl(q, base + QUADSPI_RBDR(i / 4));
>> +		val = fsl_qspi_endian_xchg(q, val);
>> +		memcpy(buf + i, &val, op->data.nbytes - i);
>> +	}
>> +}
>> +
>> +static int fsl_qspi_do_op(struct fsl_qspi *q, const struct spi_mem_op
>> +*op) {
>> +	void __iomem *base = q->iobase;
>> +	int err = 0;
>> +
>> +	init_completion(&q->c);
>> +
>> +	/*
>> +	 * Always start the sequence at the same index since we update
>> +	 * the LUT at each exec_op() call. And also specify the DATA
>> +	 * length, since it's has not been specified in the LUT.
>> +	 */
>> +	qspi_writel(q, op->data.nbytes | QUADSPI_IPCR_SEQID(SEQID_LUT),
>> +		    base + QUADSPI_IPCR);
>> +
>> +	/* Wait for the interrupt. */
>> +	if (!wait_for_completion_timeout(&q->c, msecs_to_jiffies(1000)))
>> +		err = -ETIMEDOUT;
>> +
>> +	if (!err && op->data.nbytes && op->data.dir == SPI_MEM_DATA_IN)
>> +		fsl_qspi_read_rxfifo(q, op);
>> +
>> +	return err;
>> +}
>> +
>> +static int fsl_qspi_readl_poll_tout(struct fsl_qspi *q, void __iomem *base,
>> +				    u32 mask, u32 delay_us, u32 timeout_us) {
>> +	u32 reg;
>> +
>> +	if (!q->devtype_data->little_endian)
>> +		mask = (u32)cpu_to_be32(mask);
>> +
> 
> reg is being used as an un-initialized variable, didn't it needs to be initialized with some proper value?

No, it does not need to be initialized. This is only to assign some 
memory for the readx_poll_timeout() macro: [1].

[1] 
https://elixir.bootlin.com/linux/latest/source/include/linux/iopoll.h#L50

> 
>> +	return readl_poll_timeout(base, reg, !(reg & mask), delay_us,
>> +				  timeout_us);
>> +}
>> +
> 
> --
> Regards
> Yogesh Gaur.
> 
> [...]
> 

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