[v2,1/2] nvmem: add driver for JZ4780 efuse
diff mbox series

Message ID 20171228212954.2922-2-malat@debian.org
State New, archived
Headers show
Series
  • Add efuse driver for Ingenic JZ4780 SoC
Related show

Commit Message

Mathieu Malaterre Dec. 28, 2017, 9:29 p.m. UTC
From: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>

This patch brings support for the JZ4780 efuse. Currently it only expose
a read only access to the entire 8K bits efuse memory.

Tested-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Signed-off-by: Mathieu Malaterre <malat@debian.org>
---
 .../ABI/testing/sysfs-driver-jz4780-efuse          |  16 ++
 .../bindings/nvmem/ingenic,jz4780-efuse.txt        |  17 ++
 MAINTAINERS                                        |   5 +
 arch/mips/boot/dts/ingenic/jz4780.dtsi             |  40 ++-
 drivers/nvmem/Kconfig                              |  10 +
 drivers/nvmem/Makefile                             |   2 +
 drivers/nvmem/jz4780-efuse.c                       | 305 +++++++++++++++++++++
 7 files changed, 383 insertions(+), 12 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-driver-jz4780-efuse
 create mode 100644 Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
 create mode 100644 drivers/nvmem/jz4780-efuse.c

Comments

Marcin Nowakowski Dec. 29, 2017, 12:35 p.m. UTC | #1
Hi Mathieu,

On 28.12.2017 22:29, Mathieu Malaterre wrote:

> --- /dev/null
> +++ b/drivers/nvmem/jz4780-efuse.c
> @@ -0,0 +1,305 @@
> +/*
> + * JZ4780 EFUSE Memory Support driver
> + *
> + * Copyright (c) 2017 PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
> + *
> + * 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.
> + */
> +

Can you use SPDX identifier instead?

> +/*
> + * 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/delay.h>
> +#include <linux/device.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/nvmem-provider.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/timer.h>
> +
> +#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_SEG1_OFF		0x00	/* 64 bit Random Number */
> +#define JZ_EFUSE_SEG2_OFF		0x08	/* 128 bit Ingenic Chip ID */
> +#define JZ_EFUSE_SEG3_OFF		0x18	/* 128 bit Customer ID */
> +#define JZ_EFUSE_SEG4_OFF		0x28	/* 3520 bit Reserved */
> +#define JZ_EFUSE_SEG5_OFF		0x1E0	/* 8 bit Protect Segment */
> +#define JZ_EFUSE_SEG6_OFF		0x1E1	/* 2296 bit HDMI Key */
> +#define JZ_EFUSE_SEG7_OFF		0x300	/* 2048 bit Security boot key */
> +#define JZ_EFUSE_END_ADDR		0x5FF
> +
> +#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
> +#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)
> +
> +#define JZ_EFUSE_WORD_SIZE		16
> +#define JZ_EFUSE_STRIDE			8
> +
> +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;
> +	int timeout = 1000;
> +	int size = 32;
> +
> +	/* 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);
> +	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))
> +			 = readl(efuse->iomem + JZ_EFUDATA(i));
> +
> +	return 0;
> +}
> +
> +static unsigned int segments[][2] = {

const?

> +		/* offset	, size in bytes */
> +		{ JZ_EFUSE_SEG1_OFF,   64 >> 3 }, /* bit Random Number */
> +		{ JZ_EFUSE_SEG2_OFF,  128 >> 3 }, /* bit Ingenic Chip ID */
> +		{ JZ_EFUSE_SEG3_OFF,  128 >> 3 }, /* bit Customer ID */
> +		{ JZ_EFUSE_SEG4_OFF, 3520 >> 3 }, /* bit Reserved */
> +		{ JZ_EFUSE_SEG5_OFF,    8 >> 3 }, /* bit Protect Segment */
> +		{ JZ_EFUSE_SEG6_OFF, 2296 >> 3 }, /* bit HDMI Key */
> +		{ JZ_EFUSE_SEG7_OFF, 2048 >> 3 }  /* bit Security boot key */
> +};
> +
> +#define MAX(x, y) (((x) > (y)) ? (x) : (y))
> +#define MIN(x, y) (((x) < (y)) ? (x) : (y))
> +
> +/* PM recommends read/write each segment separately */
> +static int jz4780_efuse_read_segment(struct jz4780_efuse *efuse, int segid,
> +	unsigned int *offset, char *out, size_t *bytes)
> +{
> +	char buf[32];
> +	unsigned int lpos, buflen, ncount, remain;
> +	unsigned int *segment = segments[segid];
> +	int j;
> +	char *cur = out;
> +	int ret;
> +
> +	if (*bytes == 0 ||
> +		(*offset < segment[0] || *offset >= segment[0] + segment[1])) {
> +		// nothing to see, move along
> +		return 0;
> +	}
> +	lpos = MAX(segment[0], *offset);
> +	buflen = MIN(segment[1], *bytes);

if *offset > segment[0] then you may read past the current segment.
On the other hand some segments are smaller than 32 bytes, so when 
jz4780_efuse_read_32bytes() is used, there will often be accesses across 
segment boundaries.
For this reason I don't see much point in having this split for segment 
reads. If it is really recommended/required (I haven't read the SoC's 
PM) then the read_32bytes() method needs to be changed to allow reads of 
any length (which would allow simplifying this method a lot).
Alternatively if there isn't really such requirement, you could just 
read the whole memory without worrying about segment boundaries.

> +	ncount = buflen / 32;
> +	remain = buflen % 32;
> +
> +	for (j = 0; j < ncount ; ++j) {
> +		ret = jz4780_efuse_read_32bytes(efuse, buf, lpos);
> +		if (ret < 0)
> +			return ret;
> +
> +		memcpy(cur, buf, sizeof(buf));
> +		cur += sizeof(buf);
> +		lpos += sizeof(buf);
> +		}
> +	if (remain) {
> +		ret = jz4780_efuse_read_32bytes(efuse, buf, lpos);
> +		if (ret < 0)
> +			return ret;
> +
> +		memcpy(cur, buf, remain);
> +		cur += remain;
> +		}
> +	*offset += buflen;
> +	*bytes -= buflen;
> +	return buflen;
> +}
> +
> +/* main entry point */
> +static int jz4780_efuse_read(void *context, unsigned int offset,
> +					void *val, size_t bytes)
> +{
> +	static const int nsegments = sizeof(segments) / sizeof(*segments);

any particular reason nsegments is static?

> +	struct jz4780_efuse *efuse = context;
> +	char *cur = val;
> +	int i, ret;
> +
> +	for (i = 0; i < nsegments; ++i) {
> +		ret = jz4780_efuse_read_segment(efuse, i, &offset, cur, &bytes);
> +		if (ret < 0)
> +			return ret;
> +		cur += ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static struct nvmem_config jz4780_efuse_nvmem_config = {
> +	.name = "jz4780-efuse",
> +	.read_only = true,
> +	.word_size = JZ_EFUSE_WORD_SIZE,
> +	.stride = JZ_EFUSE_STRIDE,
> +	.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);
> +
> +	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.size = 1024;
> +	jz4780_efuse_nvmem_config.dev = &pdev->dev;
> +	jz4780_efuse_nvmem_config.priv = efuse;
> +
> +	nvmem = nvmem_register(&jz4780_efuse_nvmem_config);
> +	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);
> +
> +	return nvmem_unregister(nvmem);
> +}
> +
> +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@gmail.com>");
> +MODULE_DESCRIPTION("Ingenic JZ4780 efuse driver");
> +MODULE_LICENSE("GPL v2");
>
Srinivas Kandagatla Jan. 2, 2018, 12:02 p.m. UTC | #2
On 28/12/17 21:29, Mathieu Malaterre wrote:
> From: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
> 
> This patch brings support for the JZ4780 efuse. Currently it only expose
> a read only access to the entire 8K bits efuse memory.
> 
> Tested-by: Mathieu Malaterre <malat@debian.org>
> Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
> Signed-off-by: Mathieu Malaterre <malat@debian.org>
> ---
Please split this patch, as you are mixing code, documentation, dts and 
MAINTAINER changes here.

Without which patch can not be reviewed!!


Thanks,
Srini

>   .../ABI/testing/sysfs-driver-jz4780-efuse          |  16 ++

>   .../bindings/nvmem/ingenic,jz4780-efuse.txt        |  17 ++
>   MAINTAINERS                                        |   5 +
>   arch/mips/boot/dts/ingenic/jz4780.dtsi             |  40 ++-
>   drivers/nvmem/Kconfig                              |  10 +
>   drivers/nvmem/Makefile                             |   2 +
>   drivers/nvmem/jz4780-efuse.c                       | 305 +++++++++++++++++++++
>   7 files changed, 383 insertions(+), 12 deletions(-)
...
PrasannaKumar Muralidharan Jan. 2, 2018, 4:17 p.m. UTC | #3
Hi Srini,

On 2 January 2018 at 17:32, Srinivas Kandagatla
<srinivas.kandagatla@linaro.org> wrote:
>
>
> On 28/12/17 21:29, Mathieu Malaterre wrote:
>>
>> From: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>>
>> This patch brings support for the JZ4780 efuse. Currently it only expose
>> a read only access to the entire 8K bits efuse memory.
>>
>> Tested-by: Mathieu Malaterre <malat@debian.org>
>> Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>> Signed-off-by: Mathieu Malaterre <malat@debian.org>
>> ---
>
> Please split this patch, as you are mixing code, documentation, dts and
> MAINTAINER changes here.
>
> Without which patch can not be reviewed!!

Sure, will do it soon.

>
> Thanks,
> Srini
>
>>   .../ABI/testing/sysfs-driver-jz4780-efuse          |  16 ++
>
>
>>   .../bindings/nvmem/ingenic,jz4780-efuse.txt        |  17 ++
>>   MAINTAINERS                                        |   5 +
>>   arch/mips/boot/dts/ingenic/jz4780.dtsi             |  40 ++-
>>   drivers/nvmem/Kconfig                              |  10 +
>>   drivers/nvmem/Makefile                             |   2 +
>>   drivers/nvmem/jz4780-efuse.c                       | 305
>> +++++++++++++++++++++
>>   7 files changed, 383 insertions(+), 12 deletions(-)
>
> ...

Regards,
PrasannaKumar
Rob Herring Jan. 3, 2018, 8:02 p.m. UTC | #4
On Thu, Dec 28, 2017 at 10:29:52PM +0100, Mathieu Malaterre wrote:
> From: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
> 
> This patch brings support for the JZ4780 efuse. Currently it only expose
> a read only access to the entire 8K bits efuse memory.
> 
> Tested-by: Mathieu Malaterre <malat@debian.org>
> Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
> Signed-off-by: Mathieu Malaterre <malat@debian.org>
> ---
>  .../ABI/testing/sysfs-driver-jz4780-efuse          |  16 ++
>  .../bindings/nvmem/ingenic,jz4780-efuse.txt        |  17 ++

Please split bindings to separate patch.

>  MAINTAINERS                                        |   5 +
>  arch/mips/boot/dts/ingenic/jz4780.dtsi             |  40 ++-

dts files should also be separate.

>  drivers/nvmem/Kconfig                              |  10 +
>  drivers/nvmem/Makefile                             |   2 +
>  drivers/nvmem/jz4780-efuse.c                       | 305 +++++++++++++++++++++
>  7 files changed, 383 insertions(+), 12 deletions(-)
>  create mode 100644 Documentation/ABI/testing/sysfs-driver-jz4780-efuse
>  create mode 100644 Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
>  create mode 100644 drivers/nvmem/jz4780-efuse.c
> 
> diff --git a/Documentation/ABI/testing/sysfs-driver-jz4780-efuse b/Documentation/ABI/testing/sysfs-driver-jz4780-efuse
> new file mode 100644
> index 000000000000..bb6f5d6ceea0
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-driver-jz4780-efuse
> @@ -0,0 +1,16 @@
> +What:		/sys/devices/*/<our-device>/nvmem
> +Date:		December 2017
> +Contact:	PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
> +Description:	read-only access to the efuse on the Ingenic JZ4780 SoC
> +		The SoC has a one time programmable 8K efuse that is
> +		split into segments. The driver supports read only.
> +		The segments are
> +		0x000   64 bit Random Number
> +		0x008  128 bit Ingenic Chip ID
> +		0x018  128 bit Customer ID
> +		0x028 3520 bit Reserved
> +		0x1E0    8 bit Protect Segment
> +		0x1E1 2296 bit HDMI Key
> +		0x300 2048 bit Security boot key

Why do these need to be exposed to userspace?

sysfs is 1 value per file and this is lots of different things. 

We already have ways to feed random data (entropy) to the system. And we 
have a way to expose SoC ID info to userspace (socdev).

> +Users:		any user space application which wants to read the Chip
> +		and Customer ID
> diff --git a/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt b/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
> new file mode 100644
> index 000000000000..cd6d67ec22fc
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
> @@ -0,0 +1,17 @@
> +Ingenic JZ EFUSE driver bindings
> +
> +Required properties:
> +- "compatible"		Must be set to "ingenic,jz4780-efuse"
> +- "reg"			Register location and length
> +- "clocks"		Handle for the ahb clock for the efuse.
> +- "clock-names"		Must be "bus_clk"
> +
> +Example:
> +
> +efuse: efuse@134100d0 {
> +	compatible = "ingenic,jz4780-efuse";
> +	reg = <0x134100D0 0xFF>;
> +
> +	clocks = <&cgu JZ4780_CLK_AHB2>;
> +	clock-names = "bus_clk";
> +};
> diff --git a/MAINTAINERS b/MAINTAINERS
> index a6e86e20761e..7a050c20c533 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -6902,6 +6902,11 @@ M:	Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
>  S:	Maintained
>  F:	drivers/dma/dma-jz4780.c
>  
> +INGENIC JZ4780 EFUSE Driver
> +M:	PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
> +S:	Maintained
> +F:	drivers/nvmem/jz4780-efuse.c

Binding file?

> +
>  INGENIC JZ4780 NAND DRIVER
>  M:	Harvey Hunt <harveyhuntnexus@gmail.com>
>  L:	linux-mtd@lists.infradead.org
> diff --git a/arch/mips/boot/dts/ingenic/jz4780.dtsi b/arch/mips/boot/dts/ingenic/jz4780.dtsi
> index 9b5794667aee..3fb9d916a2ea 100644
> --- a/arch/mips/boot/dts/ingenic/jz4780.dtsi
> +++ b/arch/mips/boot/dts/ingenic/jz4780.dtsi
> @@ -224,21 +224,37 @@
>  		reg = <0x10002000 0x100>;
>  	};
>  
> -	nemc: nemc@13410000 {
> -		compatible = "ingenic,jz4780-nemc";
> -		reg = <0x13410000 0x10000>;
> -		#address-cells = <2>;
> +
> +	ahb2: ahb2 {
> +		compatible = "simple-bus";

This is an unrelated change and should be its own patch.

> +		#address-cells = <1>;
>  		#size-cells = <1>;
> -		ranges = <1 0 0x1b000000 0x1000000
> -			  2 0 0x1a000000 0x1000000
> -			  3 0 0x19000000 0x1000000
> -			  4 0 0x18000000 0x1000000
> -			  5 0 0x17000000 0x1000000
> -			  6 0 0x16000000 0x1000000>;
> +		ranges = <>;
> +
> +		nemc: nemc@13410000 {
> +			compatible = "ingenic,jz4780-nemc";
> +			reg = <0x13410000 0x10000>;
> +			#address-cells = <2>;
> +			#size-cells = <1>;
> +			ranges = <1 0 0x1b000000 0x1000000
> +				  2 0 0x1a000000 0x1000000
> +				  3 0 0x19000000 0x1000000
> +				  4 0 0x18000000 0x1000000
> +				  5 0 0x17000000 0x1000000
> +				  6 0 0x16000000 0x1000000>;
> +
> +			clocks = <&cgu JZ4780_CLK_NEMC>;
> +
> +			status = "disabled";
> +		};
>  
> -		clocks = <&cgu JZ4780_CLK_NEMC>;
> +		efuse: efuse@134100d0 {
> +			compatible = "ingenic,jz4780-efuse";
> +			reg = <0x134100d0 0xff>;

You are creating an overlapping region here with nemc above. Don't do 
that.

>  
> -		status = "disabled";
> +			clocks = <&cgu JZ4780_CLK_AHB2>;
> +			clock-names = "bus_clk";
> +		};
>  	};
>  
>  	bch: bch@134d0000 {
PrasannaKumar Muralidharan Jan. 6, 2018, 12:43 p.m. UTC | #5
Hi Rob,

On 4 January 2018 at 01:32, Rob Herring <robh@kernel.org> wrote:
> On Thu, Dec 28, 2017 at 10:29:52PM +0100, Mathieu Malaterre wrote:
>> From: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>>
>> This patch brings support for the JZ4780 efuse. Currently it only expose
>> a read only access to the entire 8K bits efuse memory.
>>
>> Tested-by: Mathieu Malaterre <malat@debian.org>
>> Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>> Signed-off-by: Mathieu Malaterre <malat@debian.org>
>> ---
>>  .../ABI/testing/sysfs-driver-jz4780-efuse          |  16 ++
>>  .../bindings/nvmem/ingenic,jz4780-efuse.txt        |  17 ++
>
> Please split bindings to separate patch.
>
>>  MAINTAINERS                                        |   5 +
>>  arch/mips/boot/dts/ingenic/jz4780.dtsi             |  40 ++-
>
> dts files should also be separate.
>
>>  drivers/nvmem/Kconfig                              |  10 +
>>  drivers/nvmem/Makefile                             |   2 +
>>  drivers/nvmem/jz4780-efuse.c                       | 305 +++++++++++++++++++++
>>  7 files changed, 383 insertions(+), 12 deletions(-)
>>  create mode 100644 Documentation/ABI/testing/sysfs-driver-jz4780-efuse
>>  create mode 100644 Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
>>  create mode 100644 drivers/nvmem/jz4780-efuse.c
>>
>> diff --git a/Documentation/ABI/testing/sysfs-driver-jz4780-efuse b/Documentation/ABI/testing/sysfs-driver-jz4780-efuse
>> new file mode 100644
>> index 000000000000..bb6f5d6ceea0
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/sysfs-driver-jz4780-efuse
>> @@ -0,0 +1,16 @@
>> +What:                /sys/devices/*/<our-device>/nvmem
>> +Date:                December 2017
>> +Contact:     PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>> +Description: read-only access to the efuse on the Ingenic JZ4780 SoC
>> +             The SoC has a one time programmable 8K efuse that is
>> +             split into segments. The driver supports read only.
>> +             The segments are
>> +             0x000   64 bit Random Number
>> +             0x008  128 bit Ingenic Chip ID
>> +             0x018  128 bit Customer ID
>> +             0x028 3520 bit Reserved
>> +             0x1E0    8 bit Protect Segment
>> +             0x1E1 2296 bit HDMI Key
>> +             0x300 2048 bit Security boot key
>
> Why do these need to be exposed to userspace?
>
> sysfs is 1 value per file and this is lots of different things.
>
> We already have ways to feed random data (entropy) to the system. And we
> have a way to expose SoC ID info to userspace (socdev).

Currently ingenic chip id is not used anywhere. The vendor BSP exposed
only chip id and customer id. Should we do the same? Please provide
your suggestion.

>> +Users:               any user space application which wants to read the Chip
>> +             and Customer ID
>> diff --git a/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt b/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
>> new file mode 100644
>> index 000000000000..cd6d67ec22fc
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
>> @@ -0,0 +1,17 @@
>> +Ingenic JZ EFUSE driver bindings
>> +
>> +Required properties:
>> +- "compatible"               Must be set to "ingenic,jz4780-efuse"
>> +- "reg"                      Register location and length
>> +- "clocks"           Handle for the ahb clock for the efuse.
>> +- "clock-names"              Must be "bus_clk"
>> +
>> +Example:
>> +
>> +efuse: efuse@134100d0 {
>> +     compatible = "ingenic,jz4780-efuse";
>> +     reg = <0x134100D0 0xFF>;
>> +
>> +     clocks = <&cgu JZ4780_CLK_AHB2>;
>> +     clock-names = "bus_clk";
>> +};
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index a6e86e20761e..7a050c20c533 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -6902,6 +6902,11 @@ M:     Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
>>  S:   Maintained
>>  F:   drivers/dma/dma-jz4780.c
>>
>> +INGENIC JZ4780 EFUSE Driver
>> +M:   PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>> +S:   Maintained
>> +F:   drivers/nvmem/jz4780-efuse.c
>
> Binding file?

Sorry, missed it. Will add it.

>> +
>>  INGENIC JZ4780 NAND DRIVER
>>  M:   Harvey Hunt <harveyhuntnexus@gmail.com>
>>  L:   linux-mtd@lists.infradead.org
>> diff --git a/arch/mips/boot/dts/ingenic/jz4780.dtsi b/arch/mips/boot/dts/ingenic/jz4780.dtsi
>> index 9b5794667aee..3fb9d916a2ea 100644
>> --- a/arch/mips/boot/dts/ingenic/jz4780.dtsi
>> +++ b/arch/mips/boot/dts/ingenic/jz4780.dtsi
>> @@ -224,21 +224,37 @@
>>               reg = <0x10002000 0x100>;
>>       };
>>
>> -     nemc: nemc@13410000 {
>> -             compatible = "ingenic,jz4780-nemc";
>> -             reg = <0x13410000 0x10000>;
>> -             #address-cells = <2>;
>> +
>> +     ahb2: ahb2 {
>> +             compatible = "simple-bus";
>
> This is an unrelated change and should be its own patch.

The efuse register address range is a subset of address range of nemc.
So decided to make nemc and efuse as nodes with parent node ahb2. This
is required for efuse driver to work. I am not able to understand what
you mean by unrelated change. Can you please explain it?

>> +             #address-cells = <1>;
>>               #size-cells = <1>;
>> -             ranges = <1 0 0x1b000000 0x1000000
>> -                       2 0 0x1a000000 0x1000000
>> -                       3 0 0x19000000 0x1000000
>> -                       4 0 0x18000000 0x1000000
>> -                       5 0 0x17000000 0x1000000
>> -                       6 0 0x16000000 0x1000000>;
>> +             ranges = <>;
>> +
>> +             nemc: nemc@13410000 {
>> +                     compatible = "ingenic,jz4780-nemc";
>> +                     reg = <0x13410000 0x10000>;
>> +                     #address-cells = <2>;
>> +                     #size-cells = <1>;
>> +                     ranges = <1 0 0x1b000000 0x1000000
>> +                               2 0 0x1a000000 0x1000000
>> +                               3 0 0x19000000 0x1000000
>> +                               4 0 0x18000000 0x1000000
>> +                               5 0 0x17000000 0x1000000
>> +                               6 0 0x16000000 0x1000000>;
>> +
>> +                     clocks = <&cgu JZ4780_CLK_NEMC>;
>> +
>> +                     status = "disabled";
>> +             };
>>
>> -             clocks = <&cgu JZ4780_CLK_NEMC>;
>> +             efuse: efuse@134100d0 {
>> +                     compatible = "ingenic,jz4780-efuse";
>> +                     reg = <0x134100d0 0xff>;
>
> You are creating an overlapping region here with nemc above. Don't do
> that.

Should "reg = <0x13410000 0x10000>;" be used instead?

>
>>
>> -             status = "disabled";
>> +                     clocks = <&cgu JZ4780_CLK_AHB2>;
>> +                     clock-names = "bus_clk";
>> +             };
>>       };
>>
>>       bch: bch@134d0000 {

Thanks,
PrasannaKumar
Rob Herring Jan. 11, 2018, 3:08 p.m. UTC | #6
On Sat, Jan 6, 2018 at 6:43 AM, PrasannaKumar Muralidharan
<prasannatsmkumar@gmail.com> wrote:
> Hi Rob,
>
> On 4 January 2018 at 01:32, Rob Herring <robh@kernel.org> wrote:
>> On Thu, Dec 28, 2017 at 10:29:52PM +0100, Mathieu Malaterre wrote:
>>> From: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>>>
>>> This patch brings support for the JZ4780 efuse. Currently it only expose
>>> a read only access to the entire 8K bits efuse memory.
>>>
>>> Tested-by: Mathieu Malaterre <malat@debian.org>
>>> Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>>> Signed-off-by: Mathieu Malaterre <malat@debian.org>
>>> ---
>>>  .../ABI/testing/sysfs-driver-jz4780-efuse          |  16 ++
>>>  .../bindings/nvmem/ingenic,jz4780-efuse.txt        |  17 ++
>>
>> Please split bindings to separate patch.
>>
>>>  MAINTAINERS                                        |   5 +
>>>  arch/mips/boot/dts/ingenic/jz4780.dtsi             |  40 ++-
>>
>> dts files should also be separate.
>>
>>>  drivers/nvmem/Kconfig                              |  10 +
>>>  drivers/nvmem/Makefile                             |   2 +
>>>  drivers/nvmem/jz4780-efuse.c                       | 305 +++++++++++++++++++++
>>>  7 files changed, 383 insertions(+), 12 deletions(-)
>>>  create mode 100644 Documentation/ABI/testing/sysfs-driver-jz4780-efuse
>>>  create mode 100644 Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
>>>  create mode 100644 drivers/nvmem/jz4780-efuse.c
>>>
>>> diff --git a/Documentation/ABI/testing/sysfs-driver-jz4780-efuse b/Documentation/ABI/testing/sysfs-driver-jz4780-efuse
>>> new file mode 100644
>>> index 000000000000..bb6f5d6ceea0
>>> --- /dev/null
>>> +++ b/Documentation/ABI/testing/sysfs-driver-jz4780-efuse
>>> @@ -0,0 +1,16 @@
>>> +What:                /sys/devices/*/<our-device>/nvmem
>>> +Date:                December 2017
>>> +Contact:     PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>>> +Description: read-only access to the efuse on the Ingenic JZ4780 SoC
>>> +             The SoC has a one time programmable 8K efuse that is
>>> +             split into segments. The driver supports read only.
>>> +             The segments are
>>> +             0x000   64 bit Random Number
>>> +             0x008  128 bit Ingenic Chip ID
>>> +             0x018  128 bit Customer ID
>>> +             0x028 3520 bit Reserved
>>> +             0x1E0    8 bit Protect Segment
>>> +             0x1E1 2296 bit HDMI Key
>>> +             0x300 2048 bit Security boot key
>>
>> Why do these need to be exposed to userspace?
>>
>> sysfs is 1 value per file and this is lots of different things.
>>
>> We already have ways to feed random data (entropy) to the system. And we
>> have a way to expose SoC ID info to userspace (socdev).
>
> Currently ingenic chip id is not used anywhere. The vendor BSP exposed
> only chip id and customer id. Should we do the same? Please provide
> your suggestion.

No. Don't create an ABI if you don't really need it.

>
>>> +Users:               any user space application which wants to read the Chip
>>> +             and Customer ID
>>> diff --git a/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt b/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
>>> new file mode 100644
>>> index 000000000000..cd6d67ec22fc
>>> --- /dev/null
>>> +++ b/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
>>> @@ -0,0 +1,17 @@
>>> +Ingenic JZ EFUSE driver bindings
>>> +
>>> +Required properties:
>>> +- "compatible"               Must be set to "ingenic,jz4780-efuse"
>>> +- "reg"                      Register location and length
>>> +- "clocks"           Handle for the ahb clock for the efuse.
>>> +- "clock-names"              Must be "bus_clk"
>>> +
>>> +Example:
>>> +
>>> +efuse: efuse@134100d0 {
>>> +     compatible = "ingenic,jz4780-efuse";
>>> +     reg = <0x134100D0 0xFF>;
>>> +
>>> +     clocks = <&cgu JZ4780_CLK_AHB2>;
>>> +     clock-names = "bus_clk";
>>> +};
>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>> index a6e86e20761e..7a050c20c533 100644
>>> --- a/MAINTAINERS
>>> +++ b/MAINTAINERS
>>> @@ -6902,6 +6902,11 @@ M:     Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
>>>  S:   Maintained
>>>  F:   drivers/dma/dma-jz4780.c
>>>
>>> +INGENIC JZ4780 EFUSE Driver
>>> +M:   PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>>> +S:   Maintained
>>> +F:   drivers/nvmem/jz4780-efuse.c
>>
>> Binding file?
>
> Sorry, missed it. Will add it.
>
>>> +
>>>  INGENIC JZ4780 NAND DRIVER
>>>  M:   Harvey Hunt <harveyhuntnexus@gmail.com>
>>>  L:   linux-mtd@lists.infradead.org
>>> diff --git a/arch/mips/boot/dts/ingenic/jz4780.dtsi b/arch/mips/boot/dts/ingenic/jz4780.dtsi
>>> index 9b5794667aee..3fb9d916a2ea 100644
>>> --- a/arch/mips/boot/dts/ingenic/jz4780.dtsi
>>> +++ b/arch/mips/boot/dts/ingenic/jz4780.dtsi
>>> @@ -224,21 +224,37 @@
>>>               reg = <0x10002000 0x100>;
>>>       };
>>>
>>> -     nemc: nemc@13410000 {
>>> -             compatible = "ingenic,jz4780-nemc";
>>> -             reg = <0x13410000 0x10000>;
>>> -             #address-cells = <2>;
>>> +
>>> +     ahb2: ahb2 {
>>> +             compatible = "simple-bus";
>>
>> This is an unrelated change and should be its own patch.
>
> The efuse register address range is a subset of address range of nemc.
> So decided to make nemc and efuse as nodes with parent node ahb2. This
> is required for efuse driver to work. I am not able to understand what
> you mean by unrelated change. Can you please explain it?
>
>>> +             #address-cells = <1>;
>>>               #size-cells = <1>;
>>> -             ranges = <1 0 0x1b000000 0x1000000
>>> -                       2 0 0x1a000000 0x1000000
>>> -                       3 0 0x19000000 0x1000000
>>> -                       4 0 0x18000000 0x1000000
>>> -                       5 0 0x17000000 0x1000000
>>> -                       6 0 0x16000000 0x1000000>;
>>> +             ranges = <>;
>>> +
>>> +             nemc: nemc@13410000 {
>>> +                     compatible = "ingenic,jz4780-nemc";
>>> +                     reg = <0x13410000 0x10000>;
>>> +                     #address-cells = <2>;
>>> +                     #size-cells = <1>;
>>> +                     ranges = <1 0 0x1b000000 0x1000000
>>> +                               2 0 0x1a000000 0x1000000
>>> +                               3 0 0x19000000 0x1000000
>>> +                               4 0 0x18000000 0x1000000
>>> +                               5 0 0x17000000 0x1000000
>>> +                               6 0 0x16000000 0x1000000>;
>>> +
>>> +                     clocks = <&cgu JZ4780_CLK_NEMC>;
>>> +
>>> +                     status = "disabled";
>>> +             };
>>>
>>> -             clocks = <&cgu JZ4780_CLK_NEMC>;
>>> +             efuse: efuse@134100d0 {
>>> +                     compatible = "ingenic,jz4780-efuse";
>>> +                     reg = <0x134100d0 0xff>;
>>
>> You are creating an overlapping region here with nemc above. Don't do
>> that.
>
> Should "reg = <0x13410000 0x10000>;" be used instead?

No, that still overlaps with nemc. What's in registers 0x00-0xcf and
0x1d0-0xffff? Either get rid of this node altogether and make the
driver for nemc also instantiate the efuse driver (DT is not the only
way to instantiate drivers), or create sub-nodes under nemc for each
distinct h/w block in the 13410000-13420000 address space.

Or a third option is make nemc reg:

reg = <0x13410000 0xd0>, <0x134101d0 0xfe30>;

But I suspect that is wrong and you probably have some other function in there.

Rob
PrasannaKumar Muralidharan Jan. 17, 2018, 5:31 p.m. UTC | #7
Hi Rob,

On 11 January 2018 at 20:38, Rob Herring <robh@kernel.org> wrote:
> On Sat, Jan 6, 2018 at 6:43 AM, PrasannaKumar Muralidharan
> <prasannatsmkumar@gmail.com> wrote:
>> Hi Rob,
>>
>> On 4 January 2018 at 01:32, Rob Herring <robh@kernel.org> wrote:
>>> On Thu, Dec 28, 2017 at 10:29:52PM +0100, Mathieu Malaterre wrote:
>>>> From: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>>>>
>>>> This patch brings support for the JZ4780 efuse. Currently it only expose
>>>> a read only access to the entire 8K bits efuse memory.
>>>>
>>>> Tested-by: Mathieu Malaterre <malat@debian.org>
>>>> Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>>>> Signed-off-by: Mathieu Malaterre <malat@debian.org>
>>>> ---
>>>>  .../ABI/testing/sysfs-driver-jz4780-efuse          |  16 ++
>>>>  .../bindings/nvmem/ingenic,jz4780-efuse.txt        |  17 ++
>>>
>>> Please split bindings to separate patch.
>>>
>>>>  MAINTAINERS                                        |   5 +
>>>>  arch/mips/boot/dts/ingenic/jz4780.dtsi             |  40 ++-
>>>
>>> dts files should also be separate.
>>>
>>>>  drivers/nvmem/Kconfig                              |  10 +
>>>>  drivers/nvmem/Makefile                             |   2 +
>>>>  drivers/nvmem/jz4780-efuse.c                       | 305 +++++++++++++++++++++
>>>>  7 files changed, 383 insertions(+), 12 deletions(-)
>>>>  create mode 100644 Documentation/ABI/testing/sysfs-driver-jz4780-efuse
>>>>  create mode 100644 Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
>>>>  create mode 100644 drivers/nvmem/jz4780-efuse.c
>>>>
>>>> diff --git a/Documentation/ABI/testing/sysfs-driver-jz4780-efuse b/Documentation/ABI/testing/sysfs-driver-jz4780-efuse
>>>> new file mode 100644
>>>> index 000000000000..bb6f5d6ceea0
>>>> --- /dev/null
>>>> +++ b/Documentation/ABI/testing/sysfs-driver-jz4780-efuse
>>>> @@ -0,0 +1,16 @@
>>>> +What:                /sys/devices/*/<our-device>/nvmem
>>>> +Date:                December 2017
>>>> +Contact:     PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>>>> +Description: read-only access to the efuse on the Ingenic JZ4780 SoC
>>>> +             The SoC has a one time programmable 8K efuse that is
>>>> +             split into segments. The driver supports read only.
>>>> +             The segments are
>>>> +             0x000   64 bit Random Number
>>>> +             0x008  128 bit Ingenic Chip ID
>>>> +             0x018  128 bit Customer ID
>>>> +             0x028 3520 bit Reserved
>>>> +             0x1E0    8 bit Protect Segment
>>>> +             0x1E1 2296 bit HDMI Key
>>>> +             0x300 2048 bit Security boot key
>>>
>>> Why do these need to be exposed to userspace?
>>>
>>> sysfs is 1 value per file and this is lots of different things.
>>>
>>> We already have ways to feed random data (entropy) to the system. And we
>>> have a way to expose SoC ID info to userspace (socdev).
>>
>> Currently ingenic chip id is not used anywhere. The vendor BSP exposed
>> only chip id and customer id. Should we do the same? Please provide
>> your suggestion.
>
> No. Don't create an ABI if you don't really need it.
>
>>
>>>> +Users:               any user space application which wants to read the Chip
>>>> +             and Customer ID
>>>> diff --git a/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt b/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
>>>> new file mode 100644
>>>> index 000000000000..cd6d67ec22fc
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
>>>> @@ -0,0 +1,17 @@
>>>> +Ingenic JZ EFUSE driver bindings
>>>> +
>>>> +Required properties:
>>>> +- "compatible"               Must be set to "ingenic,jz4780-efuse"
>>>> +- "reg"                      Register location and length
>>>> +- "clocks"           Handle for the ahb clock for the efuse.
>>>> +- "clock-names"              Must be "bus_clk"
>>>> +
>>>> +Example:
>>>> +
>>>> +efuse: efuse@134100d0 {
>>>> +     compatible = "ingenic,jz4780-efuse";
>>>> +     reg = <0x134100D0 0xFF>;
>>>> +
>>>> +     clocks = <&cgu JZ4780_CLK_AHB2>;
>>>> +     clock-names = "bus_clk";
>>>> +};
>>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>>> index a6e86e20761e..7a050c20c533 100644
>>>> --- a/MAINTAINERS
>>>> +++ b/MAINTAINERS
>>>> @@ -6902,6 +6902,11 @@ M:     Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
>>>>  S:   Maintained
>>>>  F:   drivers/dma/dma-jz4780.c
>>>>
>>>> +INGENIC JZ4780 EFUSE Driver
>>>> +M:   PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>>>> +S:   Maintained
>>>> +F:   drivers/nvmem/jz4780-efuse.c
>>>
>>> Binding file?
>>
>> Sorry, missed it. Will add it.
>>
>>>> +
>>>>  INGENIC JZ4780 NAND DRIVER
>>>>  M:   Harvey Hunt <harveyhuntnexus@gmail.com>
>>>>  L:   linux-mtd@lists.infradead.org
>>>> diff --git a/arch/mips/boot/dts/ingenic/jz4780.dtsi b/arch/mips/boot/dts/ingenic/jz4780.dtsi
>>>> index 9b5794667aee..3fb9d916a2ea 100644
>>>> --- a/arch/mips/boot/dts/ingenic/jz4780.dtsi
>>>> +++ b/arch/mips/boot/dts/ingenic/jz4780.dtsi
>>>> @@ -224,21 +224,37 @@
>>>>               reg = <0x10002000 0x100>;
>>>>       };
>>>>
>>>> -     nemc: nemc@13410000 {
>>>> -             compatible = "ingenic,jz4780-nemc";
>>>> -             reg = <0x13410000 0x10000>;
>>>> -             #address-cells = <2>;
>>>> +
>>>> +     ahb2: ahb2 {
>>>> +             compatible = "simple-bus";
>>>
>>> This is an unrelated change and should be its own patch.
>>
>> The efuse register address range is a subset of address range of nemc.
>> So decided to make nemc and efuse as nodes with parent node ahb2. This
>> is required for efuse driver to work. I am not able to understand what
>> you mean by unrelated change. Can you please explain it?
>>
>>>> +             #address-cells = <1>;
>>>>               #size-cells = <1>;
>>>> -             ranges = <1 0 0x1b000000 0x1000000
>>>> -                       2 0 0x1a000000 0x1000000
>>>> -                       3 0 0x19000000 0x1000000
>>>> -                       4 0 0x18000000 0x1000000
>>>> -                       5 0 0x17000000 0x1000000
>>>> -                       6 0 0x16000000 0x1000000>;
>>>> +             ranges = <>;
>>>> +
>>>> +             nemc: nemc@13410000 {
>>>> +                     compatible = "ingenic,jz4780-nemc";
>>>> +                     reg = <0x13410000 0x10000>;
>>>> +                     #address-cells = <2>;
>>>> +                     #size-cells = <1>;
>>>> +                     ranges = <1 0 0x1b000000 0x1000000
>>>> +                               2 0 0x1a000000 0x1000000
>>>> +                               3 0 0x19000000 0x1000000
>>>> +                               4 0 0x18000000 0x1000000
>>>> +                               5 0 0x17000000 0x1000000
>>>> +                               6 0 0x16000000 0x1000000>;
>>>> +
>>>> +                     clocks = <&cgu JZ4780_CLK_NEMC>;
>>>> +
>>>> +                     status = "disabled";
>>>> +             };
>>>>
>>>> -             clocks = <&cgu JZ4780_CLK_NEMC>;
>>>> +             efuse: efuse@134100d0 {
>>>> +                     compatible = "ingenic,jz4780-efuse";
>>>> +                     reg = <0x134100d0 0xff>;
>>>
>>> You are creating an overlapping region here with nemc above. Don't do
>>> that.
>>
>> Should "reg = <0x13410000 0x10000>;" be used instead?
>
> No, that still overlaps with nemc. What's in registers 0x00-0xcf and
> 0x1d0-0xffff? Either get rid of this node altogether and make the
> driver for nemc also instantiate the efuse driver (DT is not the only
> way to instantiate drivers), or create sub-nodes under nemc for each
> distinct h/w block in the 13410000-13420000 address space.

My idea was not to change nemc driver.

By "create sub-nodes under nemc" do you mean something like below?
nemc: nemc@13410000 {
                     compatible = "ingenic,jz4780-nemc";
                     reg = <0x13410000 0x10000>;
                     <...>
                     status = "disabled";

                     efuse: efuse@134101d0 {
                                          compatible = "ingenic,jz4780-efuse";
                                          reg = <0x134100d0 0xff>;
                     }
}

Will this instantiate efuse driver? I do not know how to do that with
sub-node. I will explore more on this.

> Or a third option is make nemc reg:
>
> reg = <0x13410000 0xd0>, <0x134101d0 0xfe30>;
>
> But I suspect that is wrong and you probably have some other function in there.
>
> Rob

If the efuse block were to use a different base register address (that
does not overlap with nemc register range) in future SoC how the node
should be? Using nemc to instantiate efuse won't be the best choice if
that happens.

Thanks,
PrasannaKumar
Rob Herring Jan. 18, 2018, 1:59 a.m. UTC | #8
On Wed, Jan 17, 2018 at 11:31 AM, PrasannaKumar Muralidharan
<prasannatsmkumar@gmail.com> wrote:
> Hi Rob,
>
> On 11 January 2018 at 20:38, Rob Herring <robh@kernel.org> wrote:
>> On Sat, Jan 6, 2018 at 6:43 AM, PrasannaKumar Muralidharan
>> <prasannatsmkumar@gmail.com> wrote:
>>> Hi Rob,
>>>
>>> On 4 January 2018 at 01:32, Rob Herring <robh@kernel.org> wrote:
>>>> On Thu, Dec 28, 2017 at 10:29:52PM +0100, Mathieu Malaterre wrote:
>>>>> From: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>

[...]

>>>>> +             nemc: nemc@13410000 {
>>>>> +                     compatible = "ingenic,jz4780-nemc";
>>>>> +                     reg = <0x13410000 0x10000>;
>>>>> +                     #address-cells = <2>;
>>>>> +                     #size-cells = <1>;
>>>>> +                     ranges = <1 0 0x1b000000 0x1000000
>>>>> +                               2 0 0x1a000000 0x1000000
>>>>> +                               3 0 0x19000000 0x1000000
>>>>> +                               4 0 0x18000000 0x1000000
>>>>> +                               5 0 0x17000000 0x1000000
>>>>> +                               6 0 0x16000000 0x1000000>;
>>>>> +
>>>>> +                     clocks = <&cgu JZ4780_CLK_NEMC>;
>>>>> +
>>>>> +                     status = "disabled";
>>>>> +             };
>>>>>
>>>>> -             clocks = <&cgu JZ4780_CLK_NEMC>;
>>>>> +             efuse: efuse@134100d0 {
>>>>> +                     compatible = "ingenic,jz4780-efuse";
>>>>> +                     reg = <0x134100d0 0xff>;
>>>>
>>>> You are creating an overlapping region here with nemc above. Don't do
>>>> that.
>>>
>>> Should "reg = <0x13410000 0x10000>;" be used instead?
>>
>> No, that still overlaps with nemc. What's in registers 0x00-0xcf and
>> 0x1d0-0xffff? Either get rid of this node altogether and make the
>> driver for nemc also instantiate the efuse driver (DT is not the only
>> way to instantiate drivers), or create sub-nodes under nemc for each
>> distinct h/w block in the 13410000-13420000 address space.
>
> My idea was not to change nemc driver.
>
> By "create sub-nodes under nemc" do you mean something like below?

Yes.

> nemc: nemc@13410000 {
>                      compatible = "ingenic,jz4780-nemc";
>                      reg = <0x13410000 0x10000>;
>                      <...>
>                      status = "disabled";

Though having disabled here is strange. We'd normally ignore all the
child nodes.

>
>                      efuse: efuse@134101d0 {
>                                           compatible = "ingenic,jz4780-efuse";
>                                           reg = <0x134100d0 0xff>;
>                      }
> }
>
> Will this instantiate efuse driver? I do not know how to do that with
> sub-node. I will explore more on this.

The nemc driver just needs to call of_platform_default_populate.

>> Or a third option is make nemc reg:
>>
>> reg = <0x13410000 0xd0>, <0x134101d0 0xfe30>;
>>
>> But I suspect that is wrong and you probably have some other function in there.
>>
>> Rob
>
> If the efuse block were to use a different base register address (that
> does not overlap with nemc register range) in future SoC how the node
> should be? Using nemc to instantiate efuse won't be the best choice if
> that happens.

Then you will have a different compatible for nemc (because it is
different) and then the driver should skip the above step.

Rob
PrasannaKumar Muralidharan Jan. 20, 2018, 8:11 a.m. UTC | #9
On 11 January 2018 at 20:38, Rob Herring <robh@kernel.org> wrote:
> On Sat, Jan 6, 2018 at 6:43 AM, PrasannaKumar Muralidharan
> <prasannatsmkumar@gmail.com> wrote:
>> Hi Rob,
>>
>> On 4 January 2018 at 01:32, Rob Herring <robh@kernel.org> wrote:
>>> On Thu, Dec 28, 2017 at 10:29:52PM +0100, Mathieu Malaterre wrote:
>>>> From: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>>>>
>>>> This patch brings support for the JZ4780 efuse. Currently it only expose
>>>> a read only access to the entire 8K bits efuse memory.
>>>>
>>>> Tested-by: Mathieu Malaterre <malat@debian.org>
>>>> Signed-off-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>>>> Signed-off-by: Mathieu Malaterre <malat@debian.org>
>>>> ---
>>>>  .../ABI/testing/sysfs-driver-jz4780-efuse          |  16 ++
>>>>  .../bindings/nvmem/ingenic,jz4780-efuse.txt        |  17 ++
>>>
>>> Please split bindings to separate patch.
>>>
>>>>  MAINTAINERS                                        |   5 +
>>>>  arch/mips/boot/dts/ingenic/jz4780.dtsi             |  40 ++-
>>>
>>> dts files should also be separate.
>>>
>>>>  drivers/nvmem/Kconfig                              |  10 +
>>>>  drivers/nvmem/Makefile                             |   2 +
>>>>  drivers/nvmem/jz4780-efuse.c                       | 305 +++++++++++++++++++++
>>>>  7 files changed, 383 insertions(+), 12 deletions(-)
>>>>  create mode 100644 Documentation/ABI/testing/sysfs-driver-jz4780-efuse
>>>>  create mode 100644 Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
>>>>  create mode 100644 drivers/nvmem/jz4780-efuse.c
>>>>
>>>> diff --git a/Documentation/ABI/testing/sysfs-driver-jz4780-efuse b/Documentation/ABI/testing/sysfs-driver-jz4780-efuse
>>>> new file mode 100644
>>>> index 000000000000..bb6f5d6ceea0
>>>> --- /dev/null
>>>> +++ b/Documentation/ABI/testing/sysfs-driver-jz4780-efuse
>>>> @@ -0,0 +1,16 @@
>>>> +What:                /sys/devices/*/<our-device>/nvmem
>>>> +Date:                December 2017
>>>> +Contact:     PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
>>>> +Description: read-only access to the efuse on the Ingenic JZ4780 SoC
>>>> +             The SoC has a one time programmable 8K efuse that is
>>>> +             split into segments. The driver supports read only.
>>>> +             The segments are
>>>> +             0x000   64 bit Random Number
>>>> +             0x008  128 bit Ingenic Chip ID
>>>> +             0x018  128 bit Customer ID
>>>> +             0x028 3520 bit Reserved
>>>> +             0x1E0    8 bit Protect Segment
>>>> +             0x1E1 2296 bit HDMI Key
>>>> +             0x300 2048 bit Security boot key
>>>
>>> Why do these need to be exposed to userspace?
>>>
>>> sysfs is 1 value per file and this is lots of different things.
>>>
>>> We already have ways to feed random data (entropy) to the system. And we
>>> have a way to expose SoC ID info to userspace (socdev).
>>
>> Currently ingenic chip id is not used anywhere. The vendor BSP exposed
>> only chip id and customer id. Should we do the same? Please provide
>> your suggestion.
>
> No. Don't create an ABI if you don't really need it.

Rob,
MAC address of the ethernet device is stored in customer id segment of
efuse. So only customer id is needed. Do you think exposing customer
id would suffice?

Srini,
Only user would be dm900 ethernet driver (need to make changes to it
once the efuse driver goes in). There is no need to expose it to user
space. I am planning to modify nvmem core to not expose efuse if the
efuse driver chooses so. Do you think it makes sense? The need to
maintain ABI for user space disappears if such a change is introduced.

Thanks,
PrasannaKumar

Patch
diff mbox series

diff --git a/Documentation/ABI/testing/sysfs-driver-jz4780-efuse b/Documentation/ABI/testing/sysfs-driver-jz4780-efuse
new file mode 100644
index 000000000000..bb6f5d6ceea0
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-jz4780-efuse
@@ -0,0 +1,16 @@ 
+What:		/sys/devices/*/<our-device>/nvmem
+Date:		December 2017
+Contact:	PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
+Description:	read-only access to the efuse on the Ingenic JZ4780 SoC
+		The SoC has a one time programmable 8K efuse that is
+		split into segments. The driver supports read only.
+		The segments are
+		0x000   64 bit Random Number
+		0x008  128 bit Ingenic Chip ID
+		0x018  128 bit Customer ID
+		0x028 3520 bit Reserved
+		0x1E0    8 bit Protect Segment
+		0x1E1 2296 bit HDMI Key
+		0x300 2048 bit Security boot key
+Users:		any user space application which wants to read the Chip
+		and Customer ID
diff --git a/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt b/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
new file mode 100644
index 000000000000..cd6d67ec22fc
--- /dev/null
+++ b/Documentation/devicetree/bindings/nvmem/ingenic,jz4780-efuse.txt
@@ -0,0 +1,17 @@ 
+Ingenic JZ EFUSE driver bindings
+
+Required properties:
+- "compatible"		Must be set to "ingenic,jz4780-efuse"
+- "reg"			Register location and length
+- "clocks"		Handle for the ahb clock for the efuse.
+- "clock-names"		Must be "bus_clk"
+
+Example:
+
+efuse: efuse@134100d0 {
+	compatible = "ingenic,jz4780-efuse";
+	reg = <0x134100D0 0xFF>;
+
+	clocks = <&cgu JZ4780_CLK_AHB2>;
+	clock-names = "bus_clk";
+};
diff --git a/MAINTAINERS b/MAINTAINERS
index a6e86e20761e..7a050c20c533 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -6902,6 +6902,11 @@  M:	Zubair Lutfullah Kakakhel <Zubair.Kakakhel@imgtec.com>
 S:	Maintained
 F:	drivers/dma/dma-jz4780.c
 
+INGENIC JZ4780 EFUSE Driver
+M:	PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
+S:	Maintained
+F:	drivers/nvmem/jz4780-efuse.c
+
 INGENIC JZ4780 NAND DRIVER
 M:	Harvey Hunt <harveyhuntnexus@gmail.com>
 L:	linux-mtd@lists.infradead.org
diff --git a/arch/mips/boot/dts/ingenic/jz4780.dtsi b/arch/mips/boot/dts/ingenic/jz4780.dtsi
index 9b5794667aee..3fb9d916a2ea 100644
--- a/arch/mips/boot/dts/ingenic/jz4780.dtsi
+++ b/arch/mips/boot/dts/ingenic/jz4780.dtsi
@@ -224,21 +224,37 @@ 
 		reg = <0x10002000 0x100>;
 	};
 
-	nemc: nemc@13410000 {
-		compatible = "ingenic,jz4780-nemc";
-		reg = <0x13410000 0x10000>;
-		#address-cells = <2>;
+
+	ahb2: ahb2 {
+		compatible = "simple-bus";
+		#address-cells = <1>;
 		#size-cells = <1>;
-		ranges = <1 0 0x1b000000 0x1000000
-			  2 0 0x1a000000 0x1000000
-			  3 0 0x19000000 0x1000000
-			  4 0 0x18000000 0x1000000
-			  5 0 0x17000000 0x1000000
-			  6 0 0x16000000 0x1000000>;
+		ranges = <>;
+
+		nemc: nemc@13410000 {
+			compatible = "ingenic,jz4780-nemc";
+			reg = <0x13410000 0x10000>;
+			#address-cells = <2>;
+			#size-cells = <1>;
+			ranges = <1 0 0x1b000000 0x1000000
+				  2 0 0x1a000000 0x1000000
+				  3 0 0x19000000 0x1000000
+				  4 0 0x18000000 0x1000000
+				  5 0 0x17000000 0x1000000
+				  6 0 0x16000000 0x1000000>;
+
+			clocks = <&cgu JZ4780_CLK_NEMC>;
+
+			status = "disabled";
+		};
 
-		clocks = <&cgu JZ4780_CLK_NEMC>;
+		efuse: efuse@134100d0 {
+			compatible = "ingenic,jz4780-efuse";
+			reg = <0x134100d0 0xff>;
 
-		status = "disabled";
+			clocks = <&cgu JZ4780_CLK_AHB2>;
+			clock-names = "bus_clk";
+		};
 	};
 
 	bch: bch@134d0000 {
diff --git a/drivers/nvmem/Kconfig b/drivers/nvmem/Kconfig
index ff505af064ba..75400982abac 100644
--- a/drivers/nvmem/Kconfig
+++ b/drivers/nvmem/Kconfig
@@ -36,6 +36,16 @@  config NVMEM_IMX_OCOTP
 	  This driver can also be built as a module. If so, the module
 	  will be called nvmem-imx-ocotp.
 
+config JZ4780_EFUSE
+	tristate "JZ4780 EFUSE Memory Support"
+	depends on MACH_JZ4780 || COMPILE_TEST
+	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 e54dcfa6565a..3b7c18df6771 100644
--- a/drivers/nvmem/Makefile
+++ b/drivers/nvmem/Makefile
@@ -13,6 +13,8 @@  obj-$(CONFIG_NVMEM_IMX_IIM)	+= nvmem-imx-iim.o
 nvmem-imx-iim-y			:= imx-iim.o
 obj-$(CONFIG_NVMEM_IMX_OCOTP)	+= nvmem-imx-ocotp.o
 nvmem-imx-ocotp-y		:= imx-ocotp.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..2490e5fc1a88
--- /dev/null
+++ b/drivers/nvmem/jz4780-efuse.c
@@ -0,0 +1,305 @@ 
+/*
+ * JZ4780 EFUSE Memory Support driver
+ *
+ * Copyright (c) 2017 PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
+ *
+ * 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.
+ */
+
+/*
+ * 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/delay.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/timer.h>
+
+#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_SEG1_OFF		0x00	/* 64 bit Random Number */
+#define JZ_EFUSE_SEG2_OFF		0x08	/* 128 bit Ingenic Chip ID */
+#define JZ_EFUSE_SEG3_OFF		0x18	/* 128 bit Customer ID */
+#define JZ_EFUSE_SEG4_OFF		0x28	/* 3520 bit Reserved */
+#define JZ_EFUSE_SEG5_OFF		0x1E0	/* 8 bit Protect Segment */
+#define JZ_EFUSE_SEG6_OFF		0x1E1	/* 2296 bit HDMI Key */
+#define JZ_EFUSE_SEG7_OFF		0x300	/* 2048 bit Security boot key */
+#define JZ_EFUSE_END_ADDR		0x5FF
+
+#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
+#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)
+
+#define JZ_EFUSE_WORD_SIZE		16
+#define JZ_EFUSE_STRIDE			8
+
+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;
+	int timeout = 1000;
+	int size = 32;
+
+	/* 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);
+	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))
+			 = readl(efuse->iomem + JZ_EFUDATA(i));
+
+	return 0;
+}
+
+static unsigned int segments[][2] = {
+		/* offset	, size in bytes */
+		{ JZ_EFUSE_SEG1_OFF,   64 >> 3 }, /* bit Random Number */
+		{ JZ_EFUSE_SEG2_OFF,  128 >> 3 }, /* bit Ingenic Chip ID */
+		{ JZ_EFUSE_SEG3_OFF,  128 >> 3 }, /* bit Customer ID */
+		{ JZ_EFUSE_SEG4_OFF, 3520 >> 3 }, /* bit Reserved */
+		{ JZ_EFUSE_SEG5_OFF,    8 >> 3 }, /* bit Protect Segment */
+		{ JZ_EFUSE_SEG6_OFF, 2296 >> 3 }, /* bit HDMI Key */
+		{ JZ_EFUSE_SEG7_OFF, 2048 >> 3 }  /* bit Security boot key */
+};
+
+#define MAX(x, y) (((x) > (y)) ? (x) : (y))
+#define MIN(x, y) (((x) < (y)) ? (x) : (y))
+
+/* PM recommends read/write each segment separately */
+static int jz4780_efuse_read_segment(struct jz4780_efuse *efuse, int segid,
+	unsigned int *offset, char *out, size_t *bytes)
+{
+	char buf[32];
+	unsigned int lpos, buflen, ncount, remain;
+	unsigned int *segment = segments[segid];
+	int j;
+	char *cur = out;
+	int ret;
+
+	if (*bytes == 0 ||
+		(*offset < segment[0] || *offset >= segment[0] + segment[1])) {
+		// nothing to see, move along
+		return 0;
+	}
+	lpos = MAX(segment[0], *offset);
+	buflen = MIN(segment[1], *bytes);
+	ncount = buflen / 32;
+	remain = buflen % 32;
+
+	for (j = 0; j < ncount ; ++j) {
+		ret = jz4780_efuse_read_32bytes(efuse, buf, lpos);
+		if (ret < 0)
+			return ret;
+
+		memcpy(cur, buf, sizeof(buf));
+		cur += sizeof(buf);
+		lpos += sizeof(buf);
+		}
+	if (remain) {
+		ret = jz4780_efuse_read_32bytes(efuse, buf, lpos);
+		if (ret < 0)
+			return ret;
+
+		memcpy(cur, buf, remain);
+		cur += remain;
+		}
+	*offset += buflen;
+	*bytes -= buflen;
+	return buflen;
+}
+
+/* main entry point */
+static int jz4780_efuse_read(void *context, unsigned int offset,
+					void *val, size_t bytes)
+{
+	static const int nsegments = sizeof(segments) / sizeof(*segments);
+	struct jz4780_efuse *efuse = context;
+	char *cur = val;
+	int i, ret;
+
+	for (i = 0; i < nsegments; ++i) {
+		ret = jz4780_efuse_read_segment(efuse, i, &offset, cur, &bytes);
+		if (ret < 0)
+			return ret;
+		cur += ret;
+	}
+
+	return 0;
+}
+
+static struct nvmem_config jz4780_efuse_nvmem_config = {
+	.name = "jz4780-efuse",
+	.read_only = true,
+	.word_size = JZ_EFUSE_WORD_SIZE,
+	.stride = JZ_EFUSE_STRIDE,
+	.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);
+
+	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.size = 1024;
+	jz4780_efuse_nvmem_config.dev = &pdev->dev;
+	jz4780_efuse_nvmem_config.priv = efuse;
+
+	nvmem = nvmem_register(&jz4780_efuse_nvmem_config);
+	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);
+
+	return nvmem_unregister(nvmem);
+}
+
+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@gmail.com>");
+MODULE_DESCRIPTION("Ingenic JZ4780 efuse driver");
+MODULE_LICENSE("GPL v2");