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Date:   Mon, 17 Feb 2020 11:58:34 -0300
From:   Paul Cercueil <paul@...pouillou.net>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     "H. Nikolaus Schaller" <hns@...delico.com>,
        PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>,
        Mathieu Malaterre <malat@...ian.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paulburton@...nel.org>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        linux-mips@...r.kernel.org, letux-kernel@...nphoenux.org,
        kernel@...a-handheld.com
Subject: Re: [RFC v3 1/9] nvmem: add driver for JZ4780 efuse

Hi Srinivas,


Le lun., févr. 17, 2020 at 11:36, Srinivas Kandagatla 
<srinivas.kandagatla@...aro.org> a écrit :
> 
> 
> On 16/02/2020 19:20, H. Nikolaus Schaller wrote:
>> From: PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>
>> 
>> This patch brings support for the JZ4780 efuse. Currently it only 
>> exposes
>> a read only access to the entire 8K bits efuse memory and nvmem 
>> cells.
>> 
>> Tested-by: Mathieu Malaterre <malat@...ian.org>
>> Signed-off-by: PrasannaKumar Muralidharan 
>> <prasannatsmkumar@...il.com>
>> Signed-off-by: Mathieu Malaterre <malat@...ian.org>
>> Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
>> (Signed-off-by: Paul Cercueil <paul@...pouillou.net>)
>> ---
>>   drivers/nvmem/Kconfig        |  10 ++
>>   drivers/nvmem/Makefile       |   2 +
>>   drivers/nvmem/jz4780-efuse.c | 249 
>> +++++++++++++++++++++++++++++++++++
>>   3 files changed, 261 insertions(+)
>>   create mode 100644 drivers/nvmem/jz4780-efuse.c
>> 
> 
> This patch along with 2/9 should be merged into single patch.
> Also please make sure you run checkpatch.pl before sending!
> 
>> diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
>> index 35efab1ba8d9..10f8e08f5e31 100644
>> --- a/drivers/nvmem/Kconfig
>> +++ b/drivers/nvmem/Kconfig
>> @@ -55,6 +55,16 @@ config NVMEM_IMX_OCOTP_SCU
>>   	  This is a driver for the SCU On-Chip OTP Controller (OCOTP)
>>   	  available on i.MX8 SoCs.
>>   +config JZ4780_EFUSE
>> +	tristate "JZ4780 EFUSE Memory Support"
>> +	depends on MACH_JZ4780 || COMPILE_TEST
> 
> what is that this driver depends on MACH_JZ4780 board?
> 
> 
>> +	depends on HAS_IOMEM
>> +	help
>> +	  Say Y here to include support for JZ4780 efuse memory found on
>> +	  all JZ4780 SoC based devices.
>> +	  To compile this driver as a module, choose M here: the module
>> +	  will be called nvmem_jz4780_efuse.
>> +
>>   config NVMEM_LPC18XX_EEPROM
>>   	tristate "NXP LPC18XX EEPROM Memory Support"
>>   	depends on ARCH_LPC18XX || COMPILE_TEST
>> diff --git a/drivers/nvmem/Makefile b/drivers/nvmem/Makefile
>> index 6b466cd1427b..65a268d17807 100644
>> --- a/drivers/nvmem/Makefile
>> +++ b/drivers/nvmem/Makefile
>> @@ -18,6 +18,8 @@ obj-$(CONFIG_NVMEM_IMX_OCOTP)	+= nvmem-imx-ocotp.o
>>   nvmem-imx-ocotp-y		:= imx-ocotp.o
>>   obj-$(CONFIG_NVMEM_IMX_OCOTP_SCU)	+= nvmem-imx-ocotp-scu.o
>>   nvmem-imx-ocotp-scu-y		:= imx-ocotp-scu.o
>> +obj-$(CONFIG_JZ4780_EFUSE)		+= nvmem_jz4780_efuse.o
>> +nvmem_jz4780_efuse-y		:= jz4780-efuse.o
>>   obj-$(CONFIG_NVMEM_LPC18XX_EEPROM)	+= nvmem_lpc18xx_eeprom.o
>>   nvmem_lpc18xx_eeprom-y	:= lpc18xx_eeprom.o
>>   obj-$(CONFIG_NVMEM_LPC18XX_OTP)	+= nvmem_lpc18xx_otp.o
>> diff --git a/drivers/nvmem/jz4780-efuse.c 
>> b/drivers/nvmem/jz4780-efuse.c
>> new file mode 100644
>> index 000000000000..ac03e1900ef9
>> --- /dev/null
>> +++ b/drivers/nvmem/jz4780-efuse.c
>> @@ -0,0 +1,249 @@
>> +// SPDX-License-Identifier: GPL-2.0-or-later
>> +/*
>> + * JZ4780 EFUSE Memory Support driver
>> + *
>> + * Copyright (c) 2017 PrasannaKumar Muralidharan 
>> <prasannatsmkumar@...il.com>
>> + * Copyright (c) 2020 H. Nikolaus Schaller <hns@...delico.com>
>> + */
>> +
>> +/*
>> + * Currently supports JZ4780 efuse which has 8K programmable bit.
>> + * Efuse is separated into seven segments as below:
>> + *
>> + * 
>> -----------------------------------------------------------------------
>> + * | 64 bit | 128 bit | 128 bit | 3520 bit | 8 bit | 2296 bit | 
>> 2048 bit |
>> + * 
>> -----------------------------------------------------------------------
>> + *
>> + * The rom itself is accessed using a 9 bit address line and an 8 
>> word wide bus
>> + * which reads/writes based on strobes. The strobe is configured in 
>> the config
>> + * register and is based on number of cycles of the bus clock.
>> + *
>> + * Driver supports read only as the writes are done in the Factory.
>> + */
>> +
>> +#include <linux/bitops.h>
>> +#include <linux/clk.h>
>> +#include <linux/module.h>
>> +#include <linux/nvmem-provider.h>
>> +#include <linux/of.h>
>> +#include <linux/platform_device.h>
> 
> 
>> +#include <linux/regmap.h>
>> +#include <linux/timer.h>
> ?? why do we need these two headers in this patch
> 
> 
>> +
>> +#define JZ_EFUCTRL			(0x0)	/* Control Register */
>> +#define JZ_EFUCFG			(0x4)	/* Configure Register*/
>> +#define JZ_EFUSTATE			(0x8)	/* Status Register */
>> +#define JZ_EFUDATA(n)			(0xC + (n)*4)
>> +
>> +#define JZ_EFUSE_START_ADDR		0x200
>> +
>> +#define JZ_EFUSE_EFUCTRL_CS		BIT(30)
>> +#define JZ_EFUSE_EFUCTRL_ADDR_MASK	0x1FF
>> +#define JZ_EFUSE_EFUCTRL_ADDR_SHIFT	21
>> +#define JZ_EFUSE_EFUCTRL_LEN_MASK	0x1F
>> +#define JZ_EFUSE_EFUCTRL_LEN_SHIFT	16
>> +#define JZ_EFUSE_EFUCTRL_PG_EN		BIT(15)
>> +#define JZ_EFUSE_EFUCTRL_WR_EN		BIT(1)
>> +#define JZ_EFUSE_EFUCTRL_RD_EN		BIT(0)
>> +
>> +#define JZ_EFUSE_EFUCFG_INT_EN		BIT(31)
>> +#define JZ_EFUSE_EFUCFG_RD_ADJ_MASK	0xF
> 
> consider using GENMASK for these masks here.
> 
>> +#define JZ_EFUSE_EFUCFG_RD_ADJ_SHIFT	20
>> +#define JZ_EFUSE_EFUCFG_RD_STR_MASK	0xF
>> +#define JZ_EFUSE_EFUCFG_RD_STR_SHIFT	16
>> +#define JZ_EFUSE_EFUCFG_WR_ADJ_MASK	0xF
>> +#define JZ_EFUSE_EFUCFG_WR_ADJ_SHIFT	12
>> +#define JZ_EFUSE_EFUCFG_WR_STR_MASK	0xFFF
>> +#define JZ_EFUSE_EFUCFG_WR_STR_SHIFT	0
>> +
>> +#define JZ_EFUSE_EFUSTATE_WR_DONE	BIT(1)
>> +#define JZ_EFUSE_EFUSTATE_RD_DONE	BIT(0)
>> +
>> +struct jz4780_efuse {
>> +	struct device *dev;
>> +	void __iomem *iomem;
>> +	struct clk *clk;
>> +	unsigned int rd_adj;
>> +	unsigned int rd_strobe;
>> +};
>> +
>> +/* We read 32 byte chunks to avoid complexity in the driver. */
>> +static int jz4780_efuse_read_32bytes(struct jz4780_efuse *efuse, 
>> char *buf,
>> +		unsigned int addr)
>> +{
>> +	unsigned int tmp = 0;
>> +	int i = 0;
> 
> unnecessary initialization of both variables.
> 
>> +	int timeout = 1000;
>> +	int size = 32;
> 
> better to #define this STRIDE/CHUNK size. this driver seems to use 
> this value in multiple places.
> 
>> +
>> +	/* 1. Set config register */
>> +	tmp = readl(efuse->iomem + JZ_EFUCFG);
>> +	tmp &= ~((JZ_EFUSE_EFUCFG_RD_ADJ_MASK << 
>> JZ_EFUSE_EFUCFG_RD_ADJ_SHIFT)
>> +	| (JZ_EFUSE_EFUCFG_RD_STR_MASK << JZ_EFUSE_EFUCFG_RD_STR_SHIFT));
>> +	tmp |= (efuse->rd_adj << JZ_EFUSE_EFUCFG_RD_ADJ_SHIFT)
>> +	| (efuse->rd_strobe << JZ_EFUSE_EFUCFG_RD_STR_SHIFT);
> 
> very odd indenting.
> 
>> +	writel(tmp, efuse->iomem + JZ_EFUCFG);
>> +
>> +	/*
>> +	 * 2. Set control register to indicate what to read data address,
>> +	 * read data numbers and read enable.
>> +	 */
>> +	tmp = readl(efuse->iomem + JZ_EFUCTRL);
>> +	tmp &= ~(JZ_EFUSE_EFUCFG_RD_STR_SHIFT
>> +		| (JZ_EFUSE_EFUCTRL_ADDR_MASK << JZ_EFUSE_EFUCTRL_ADDR_SHIFT)
>> +		| JZ_EFUSE_EFUCTRL_PG_EN | JZ_EFUSE_EFUCTRL_WR_EN
>> +		| JZ_EFUSE_EFUCTRL_WR_EN);
>> +
>> +	/* Need to select CS bit if address accesses upper 4Kbits memory */
>> +	if (addr >= (JZ_EFUSE_START_ADDR + 512))
>> +		tmp |= JZ_EFUSE_EFUCTRL_CS;
>> +
>> +	tmp |= (addr << JZ_EFUSE_EFUCTRL_ADDR_SHIFT)
>> +		| ((size - 1) << JZ_EFUSE_EFUCTRL_LEN_SHIFT)
>> +		| JZ_EFUSE_EFUCTRL_RD_EN;
>> +	writel(tmp, efuse->iomem + JZ_EFUCTRL);
>> +
>> +	/*
>> +	 * 3. Wait status register RD_DONE set to 1 or EFUSE interrupted,
>> +	 * software can read EFUSE data buffer 0 - 8 registers.
>> +	 */
>> +	do {
>> +		tmp = readl(efuse->iomem + JZ_EFUSTATE);
>> +		usleep_range(1000, 2000);
>> +		if (timeout--)
>> +			break;
>> +	} while (!(tmp & JZ_EFUSE_EFUSTATE_RD_DONE));
>> +
>> +	if (timeout <= 0) {
>> +		dev_err(efuse->dev, "Timed out while reading\n");
>> +		return -EAGAIN;
>> +	}
>> +
>> +	for (i = 0; i < (size / 4); i++)
>> +		*((unsigned int *)(buf + i * 4))
> 
> make "unsigned int *buf32" a local variable and use it here, makes it 
> much readable code.
> 
>> +			 = readl(efuse->iomem + JZ_EFUDATA(i));
>> +
>> +	return 0;
>> +}
>> +
>> +/* main entry point */
>> +static int jz4780_efuse_read(void *context, unsigned int offset,
>> +					void *val, size_t bytes)
>> +{
>> +	struct jz4780_efuse *efuse = context;
>> +	int ret;
>> +
>> +	while (bytes > 0) {
>> +		unsigned int start = offset & ~(32 - 1);
>> +		unsigned chunk = min(bytes, (start + 32 - offset));
>> +
>> +		if (start == offset && chunk == 32) {
>> +			ret = jz4780_efuse_read_32bytes(efuse, val, start);
>> +			if (ret < 0)
>> +				return ret;
>> +
>> +		} else {
>> +			char buf[32];
>> +			ret = jz4780_efuse_read_32bytes(efuse, buf, start);
>> +			if (ret < 0)
>> +				return ret;
>> +
>> +			memcpy(val, &buf[offset - start], chunk);
>> +		}
>> +
>> +		val += chunk;
>> +		offset += chunk;
>> +		bytes -= chunk;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static struct nvmem_config jz4780_efuse_nvmem_config = {
>> +	.name = "jz4780-efuse",
>> +	.read_only = true,
> 
> this value comes from device tree bindings, do we still need  to 
> specify this here?

I think its semantic is different - devicetree specifies that you want 
the nvmem to be readonly, this one specifies that the driver cannot do 
read-write anyway.

With that said, there is no .reg_write, so .read_only will be enforced 
to 'true' anyway, so it can be removed.

-Paul

> 
>> +	.size = 1024,
>> +	.word_size = 1,
>> +	.stride = 1,
>> +	.owner = THIS_MODULE,
>> +	.reg_read = jz4780_efuse_read,
>> +};
>> +
>> +static int jz4780_efuse_probe(struct platform_device *pdev)
>> +{
>> +	struct nvmem_device *nvmem;
>> +	struct jz4780_efuse *efuse;
>> +	struct resource *res;
>> +	unsigned long clk_rate;
>> +	struct device *dev = &pdev->dev;
>> +
>> +	efuse = devm_kzalloc(&pdev->dev, sizeof(*efuse), GFP_KERNEL);
>> +	if (!efuse)
>> +		return -ENOMEM;
>> +
>> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +	efuse->iomem = devm_ioremap(&pdev->dev, res->start, 
>> resource_size(res));
>> +	if (IS_ERR(efuse->iomem))
>> +		return PTR_ERR(efuse->iomem);
>> +
>> +	efuse->clk = devm_clk_get(&pdev->dev, "bus_clk");
>> +	if (IS_ERR(efuse->clk))
>> +		return PTR_ERR(efuse->clk);
> 
> Who is enabling this clk?
> 
> 
>> +
>> +	clk_rate = clk_get_rate(efuse->clk);
>> +	/*
>> +	 * rd_adj and rd_strobe are 4 bit values
>> +	 * bus clk period * (rd_adj + 1) > 6.5ns
>> +	 * bus clk period * (rd_adj + 5 + rd_strobe) > 35ns
>> +	 */
>> +	efuse->rd_adj = (((6500 * (clk_rate / 1000000)) / 1000000) + 1) - 
>> 1;
>> +	efuse->rd_strobe = ((((35000 * (clk_rate / 1000000)) / 1000000) + 
>> 1)
>> +						- 5 - efuse->rd_adj);
>> +
>> +	if ((efuse->rd_adj > 0x1F) || (efuse->rd_strobe > 0x1F)) {
>> +		dev_err(&pdev->dev, "Cannot set clock configuration\n");
>> +		return -EINVAL;
>> +	}
>> +	efuse->dev = dev;
>> +
>> +	jz4780_efuse_nvmem_config.dev = &pdev->dev;
>> +	jz4780_efuse_nvmem_config.priv = efuse;
>> +
>> +	nvmem = nvmem_register(&jz4780_efuse_nvmem_config);
> 
> devm variant here?
> 
> 
>> +	if (IS_ERR(nvmem))
>> +		return PTR_ERR(nvmem);
>> +
>> +	platform_set_drvdata(pdev, nvmem);
>> +
>> +	return 0;
>> +}
>> +
>> +static int jz4780_efuse_remove(struct platform_device *pdev)
>> +{
>> +	struct nvmem_device *nvmem = platform_get_drvdata(pdev);
>> +
>> +	nvmem_unregister(nvmem);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct of_device_id jz4780_efuse_match[] = {
>> +	{ .compatible = "ingenic,jz4780-efuse" },
>> +	{ /* sentinel */ },
>> +};
>> +MODULE_DEVICE_TABLE(of, jz4780_efuse_match);
>> +
>> +static struct platform_driver jz4780_efuse_driver = {
>> +	.probe  = jz4780_efuse_probe,
>> +	.remove = jz4780_efuse_remove,
>> +	.driver = {
>> +		.name = "jz4780-efuse",
>> +		.of_match_table = jz4780_efuse_match,
>> +	},
>> +};
>> +module_platform_driver(jz4780_efuse_driver);
>> +
>> +MODULE_AUTHOR("PrasannaKumar Muralidharan 
>> <prasannatsmkumar@...il.com>");
>> +MODULE_AUTHOR("H. Nikolaus Schaller <hns@...delico.com>");
>> +MODULE_DESCRIPTION("Ingenic JZ4780 efuse driver");
>> +MODULE_LICENSE("GPL v2");
>> 


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