Subject: [PATCH v2 2/4] nvmem: NXP LPC18xx EEPROM memory NVMEM driver

From: [email-masked] (Srinivas Kandagatla)
Date: Mon, 26 Oct 2015 14:23:54 +0000

On 19/10/15 18:32, Ariel D'Alessandro wrote:
> This commit adds support for NXP LPC18xx EEPROM memory found in NXP
s/commit/patch

> LPC185x/3x and LPC435x/3x/2x/1x devices.
>
> EEPROM size is 16384 bytes and it can be entirely read and
> written/erased with 1 word (4 bytes) granularity. The last page
> (128 bytes) contains the EEPROM initialization data and is not writable.
>
> Erase/program time is less than 3ms. The EEPROM device requires a
> ~1500 kHz clock (min 800 kHz, max 1600 kHz) that is generated dividing
> the system bus clock by the division factor, contained in the divider
> register (minus 1 encoded).
>
> Signed-off-by: Ariel D'Alessandro <[email-masked]>
> ---
>   drivers/nvmem/Kconfig          |   9 ++
>   drivers/nvmem/Makefile         |   2 +
>   drivers/nvmem/lpc18xx_eeprom.c | 266 +++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 277 insertions(+)
>   create mode 100644 drivers/nvmem/lpc18xx_eeprom.c
>
> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
> index bc4ea58..6ff1b50 100644
> --- a/drivers/nvmem/Kconfig
> +++ b/drivers/nvmem/Kconfig
> @@ -25,6 +25,15 @@ config NVMEM_IMX_OCOTP
>   	  This driver can also be built as a module. If so, the module
>   	  will be called nvmem-imx-ocotp.
>
> +config NVMEM_LPC18XX_EEPROM
> +	tristate "NXP LPC18XX EEPROM Memory Support"
> +	depends on ARCH_LPC18XX || COMPILE_TEST
> +	help
> +	  Say Y here to include support for NXP LPC18xx EEPROM memory found in
> +	  NXP LPC185x/3x and LPC435x/3x/2x/1x devices.
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called nvmem_lpc18xx_eeprom.
> +
>   config NVMEM_MXS_OCOTP
>   	tristate "Freescale MXS On-Chip OTP Memory Support"
>   	depends on ARCH_MXS || COMPILE_TEST
> diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
> index 95dde3f..c14a556 100644
> --- a/drivers/nvmem/Makefile
> +++ b/drivers/nvmem/Makefile
> @@ -8,6 +8,8 @@ nvmem_core-y			:= core.o
>   # Devices
>   obj-$(CONFIG_NVMEM_IMX_OCOTP)	+= nvmem-imx-ocotp.o
>   nvmem-imx-ocotp-y		:= imx-ocotp.o
> +obj-$(CONFIG_NVMEM_LPC18XX_EEPROM)	+= nvmem_lpc18xx_eeprom.o
> +nvmem_lpc18xx_eeprom-y	:= lpc18xx_eeprom.o
>   obj-$(CONFIG_NVMEM_MXS_OCOTP)	+= nvmem-mxs-ocotp.o
>   nvmem-mxs-ocotp-y		:= mxs-ocotp.o
>   obj-$(CONFIG_QCOM_QFPROM)	+= nvmem_qfprom.o
> diff --git a/drivers/nvmem/lpc18xx_eeprom.c b/drivers/nvmem/lpc18xx_eeprom.c
> new file mode 100644
> index 0000000..ccdda66
> --- /dev/null
> +++ b/drivers/nvmem/lpc18xx_eeprom.c
> @@ -0,0 +1,266 @@
> +/*
> + * NXP LPC18xx/LPC43xx EEPROM memory NVMEM driver
> + *
> + * Copyright (c) 2015 Ariel D'Alessandro <[email-masked]>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published by
> + * the Free Software Foundation.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/device.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/nvmem-provider.h>
> +#include <linux/of_device.h>
Why do you need above?

Also you should probably include

  #include <linux/platform_device.h>

> +#include <linux/regmap.h>
> +#include <linux/reset.h>
> +
> +/* Registers */
> +#define LPC18XX_EEPROM_AUTOPROG		0x00c
> +#define LPC18XX_EEPROM_AUTOPROG_WORD	0x1
> +
> +#define LPC18XX_EEPROM_CLKDIV		0x014
> +
> +#define LPC18XX_EEPROM_PWRDWN		0x018
> +#define LPC18XX_EEPROM_PWRDWN_NO	0x0
> +#define LPC18XX_EEPROM_PWRDWN_YES	0x1
> +
> +/* Fixed page size (bytes) */
> +#define LPC18XX_EEPROM_PAGE_SIZE	0x80
> +
> +/* EEPROM device requires a ~1500 kHz clock (min 800 kHz, max 1600 kHz) */
> +#define LPC18XX_EEPROM_CLOCK_HZ		1500000
> +
> +struct lpc18xx_eeprom_dev {
> +	struct clk *clk;
> +	void __iomem *reg_base;
> +	void __iomem *mem_base;
> +	struct nvmem_device *nvmem;
> +	unsigned reg_bytes;
> +	unsigned val_bytes;
> +};
> +
> +static inline void lpc18xx_eeprom_writel(struct lpc18xx_eeprom_dev *eeprom,
> +					 u32 reg, u32 val)
> +{
> +	writel(val, eeprom->reg_base + reg);
> +}
I don't have a strong feeling but, I see no point to have a wrapper for 
writel which is only used in probe function.

> +
> +static int lpc18xx_eeprom_gather_write(void *context, const void *reg,
> +				       size_t reg_size, const void *val,
> +				       size_t val_size)
> +{
> +	struct lpc18xx_eeprom_dev *eeprom = context;
> +	unsigned int offset = *(u32 *)reg;
> +
> +	/* 3 ms of erase/program time between each writing */
> +	while (val_size) {
> +		writel(*(u32 *)val, eeprom->mem_base + offset);
> +		usleep_range(3000, 4000);
> +		val_size -= eeprom->val_bytes;
> +		val += eeprom->val_bytes;
> +		offset += eeprom->val_bytes;
> +	}
> +
> +	return 0;
> +}
> +
> +static int lpc18xx_eeprom_write(void *context, const void *data, size_t count)
> +{
> +	struct lpc18xx_eeprom_dev *eeprom = context;
> +	unsigned int offset = eeprom->reg_bytes;
> +
> +	if (count <= offset)
> +		return -EINVAL;
> +
> +
unnecessary new line.

> +	return lpc18xx_eeprom_gather_write(context, data, eeprom->reg_bytes,
> +					   data + offset, count - offset);
> +}
> +
> +static int lpc18xx_eeprom_read(void *context, const void *reg, size_t reg_size,
> +			       void *val, size_t val_size)
> +{
> +	struct lpc18xx_eeprom_dev *eeprom = context;
> +	unsigned int offset = *(u32 *)reg;
> +
> +	while (val_size) {
> +		*(u32 *)val = readl(eeprom->mem_base + offset);
> +		val_size -= eeprom->val_bytes;
> +		val += eeprom->val_bytes;
> +		offset += eeprom->val_bytes;
> +	}
> +
> +	return 0;
> +}
> +
> +static struct regmap_bus lpc18xx_eeprom_bus = {
> +	.write = lpc18xx_eeprom_write,
> +	.gather_write = lpc18xx_eeprom_gather_write,
> +	.read = lpc18xx_eeprom_read,
> +	.reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
> +	.val_format_endian_default = REGMAP_ENDIAN_NATIVE,
> +};
> +
> +static struct regmap_config lpc18xx_regmap_config = {
> +	.reg_bits = 32,
> +	.reg_stride = 4,
> +	.val_bits = 32,
> +};
> +
> +static bool lpc18xx_eeprom_writeable_reg(struct device *dev, unsigned int reg)
> +{
> +	/*
> +	 * The last page contains the EEPROM initialization data and is not
> +	 * writable.
> +	 */
> +	return reg <= lpc18xx_regmap_config.max_register -
> +						LPC18XX_EEPROM_PAGE_SIZE;
> +}
> +
> +static bool lpc18xx_eeprom_readable_reg(struct device *dev, unsigned int reg)
> +{
> +	return reg <= lpc18xx_regmap_config.max_register;
> +}
> +
> +static struct nvmem_config lpc18xx_nvmem_config = {
> +	.name = "lpc18xx-eeprom",
> +	.owner = THIS_MODULE,
> +};
> +
> +static const struct of_device_id lpc18xx_eeprom_of_match[] = {
> +	{ .compatible = "nxp,lpc1857-eeprom" },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, lpc18xx_eeprom_of_match);
> +
> +static int lpc18xx_eeprom_probe(struct platform_device *pdev)
> +{
> +	struct lpc18xx_eeprom_dev *eeprom;
> +	struct device *dev = &pdev->dev;
> +	struct reset_control *rst;
> +	unsigned long clk_rate;
> +	struct regmap *regmap;
> +	struct resource *res;
> +	int ret;
> +
> +	eeprom = devm_kzalloc(dev, sizeof(*eeprom), GFP_KERNEL);
> +	if (!eeprom)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "reg");
> +	eeprom->reg_base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(eeprom->reg_base))
> +		return PTR_ERR(eeprom->reg_base);
> +
> +	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "mem");
> +	eeprom->mem_base = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(eeprom->mem_base))
> +		return PTR_ERR(eeprom->mem_base);
> +
> +	eeprom->clk = devm_clk_get(&pdev->dev, "eeprom");
> +	if (IS_ERR(eeprom->clk)) {
> +		dev_err(&pdev->dev, "failed to get eeprom clock\n");
> +		return PTR_ERR(eeprom->clk);
> +	}
> +
> +	ret = clk_prepare_enable(eeprom->clk);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to prepare/enable eeprom clk: %d\n", ret);
> +		return ret;
> +	}
> +
> +	rst = devm_reset_control_get(dev, NULL);
> +	if (IS_ERR(rst)) {
> +		dev_err(dev, "failed to get reset: %ld\n", PTR_ERR(rst));
> +		ret = PTR_ERR(rst);
> +		goto err_clk;
> +	}
> +
> +	ret = reset_control_deassert(rst);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to deassert reset: %d\n", ret);
> +		goto err_clk;
> +	}
> +
> +	eeprom->val_bytes = lpc18xx_regmap_config.val_bits / 8;
> +	eeprom->reg_bytes = lpc18xx_regmap_config.reg_bits / 8;
> +
> +	/*
> +	 * Clock rate is generated by dividing the system bus clock by the
> +	 * division factor, contained in the divider register (minus 1 encoded).
> +	 */
> +	clk_rate = clk_get_rate(eeprom->clk);
> +	clk_rate = DIV_ROUND_UP(clk_rate, LPC18XX_EEPROM_CLOCK_HZ) - 1;
> +	lpc18xx_eeprom_writel(eeprom, LPC18XX_EEPROM_CLKDIV, clk_rate);
> +
> +	/*
> +	 * Writing a single word to the page will start the erase/program cycle
> +	 * automatically
> +	 */
> +	lpc18xx_eeprom_writel(eeprom, LPC18XX_EEPROM_AUTOPROG,
> +			      LPC18XX_EEPROM_AUTOPROG_WORD);
> +
> +	lpc18xx_eeprom_writel(eeprom, LPC18XX_EEPROM_PWRDWN,
> +			      LPC18XX_EEPROM_PWRDWN_NO);

Any reason not power up/dowm dynamically in 
lpc18xx_eeprom_write()/lpc18xx_eeprom_read().

This can potentially save some power.

> +
> +	lpc18xx_regmap_config.max_register = resource_size(res) - 1;
> +	lpc18xx_regmap_config.writeable_reg = lpc18xx_eeprom_writeable_reg;
> +	lpc18xx_regmap_config.readable_reg = lpc18xx_eeprom_readable_reg;
> +
> +	regmap = devm_regmap_init(dev, &lpc18xx_eeprom_bus, eeprom,
> +				  &lpc18xx_regmap_config);
> +	if (IS_ERR(regmap)) {
> +		dev_err(dev, "regmap init failed: %ld\n", PTR_ERR(regmap));
> +		ret = PTR_ERR(regmap);
> +		goto err_clk;
> +	}
> +
> +	lpc18xx_nvmem_config.dev = dev;
> +
> +	eeprom->nvmem = nvmem_register(&lpc18xx_nvmem_config);
> +	if (IS_ERR(eeprom->nvmem)) {
> +		ret = PTR_ERR(eeprom->nvmem);
> +		goto err_clk;
> +	}
> +
> +	platform_set_drvdata(pdev, eeprom);
> +
> +	return 0;
> +
> +err_clk:

Should this error path also include power down/reset assert the eeprom?

> +	clk_disable_unprepare(eeprom->clk);
> +
> +	return ret;
> +}
> +
> +static int lpc18xx_eeprom_remove(struct platform_device *pdev)
> +{
> +	struct lpc18xx_eeprom_dev *eeprom = platform_get_drvdata(pdev);
> +
> +	lpc18xx_eeprom_writel(eeprom, LPC18XX_EEPROM_PWRDWN,
> +			      LPC18XX_EEPROM_PWRDWN_YES);
> +
> +	clk_disable_unprepare(eeprom->clk);
> +
> +	return nvmem_unregister(eeprom->nvmem);

Same comment as Joachim, should the reset be asserted too?
> +}
> +
> +static struct platform_driver lpc18xx_eeprom_driver = {
> +	.probe = lpc18xx_eeprom_probe,
> +	.remove = lpc18xx_eeprom_remove,
> +	.driver = {
> +		.name = "lpc18xx-eeprom",
> +		.of_match_table = lpc18xx_eeprom_of_match,
> +	},
> +};
> +
> +module_platform_driver(lpc18xx_eeprom_driver);
> +
> +MODULE_AUTHOR("Ariel D'Alessandro <[email-masked]>");
> +MODULE_DESCRIPTION("NXP LPC18xx EEPROM memory Driver");
> +MODULE_LICENSE("GPL v2");
>