[v3,10/21] mtd: support BB SRAM on ICP DAS LP-8x4x

This provides an MTD device driver for 512kB of battery backed up SRAM
on ICPDAS LP-8X4X programmable automation controllers.

SRAM chip is connected via FPGA and is not accessible without a driver,
unlike flash memory which is wired to CPU MMU.

This SRAM becomes an excellent persisent storage of volatile process
data like counter values and sensor statuses. Storing those data in
flash or mmc card is not a viable solution.

Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
---
   v2..v3
   * no changes (except number 08/16 -> 10/21)

   v0..v2
   * use device tree
   * use devm helpers where possible

 arch/arm/boot/dts/pxa27x-lp8x4x.dts |   6 +
 arch/arm/configs/lp8x4x_defconfig   |   1 +
 drivers/mtd/devices/Kconfig         |  14 +++
 drivers/mtd/devices/Makefile        |   1 +
 drivers/mtd/devices/sram_lp8x4x.c   | 227 ++++++++++++++++++++++++++++++++++++
 5 files changed, 249 insertions(+)
 create mode 100644 drivers/mtd/devices/sram_lp8x4x.c

Hi Sergei,

On Tue, Dec 17, 2013 at 11:37:40PM +0400, Sergei Ianovich wrote:
> This provides an MTD device driver for 512kB of battery backed up SRAM
> on ICPDAS LP-8X4X programmable automation controllers.
> 
> SRAM chip is connected via FPGA and is not accessible without a driver,
> unlike flash memory which is wired to CPU MMU.
> 
> This SRAM becomes an excellent persisent storage of volatile process
> data like counter values and sensor statuses. Storing those data in
> flash or mmc card is not a viable solution.
> 
> Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
> ---
>    v2..v3
>    * no changes (except number 08/16 -> 10/21)
> 
>    v0..v2
>    * use device tree
>    * use devm helpers where possible

What's the status of this series? Is the rest of this platform support
going in via other trees yet? I have a few trivial comments, but this
driver mostly looks good as-is.

>  arch/arm/boot/dts/pxa27x-lp8x4x.dts |   6 +
>  arch/arm/configs/lp8x4x_defconfig   |   1 +
>  drivers/mtd/devices/Kconfig         |  14 +++
>  drivers/mtd/devices/Makefile        |   1 +
>  drivers/mtd/devices/sram_lp8x4x.c   | 227 ++++++++++++++++++++++++++++++++++++
>  5 files changed, 249 insertions(+)
>  create mode 100644 drivers/mtd/devices/sram_lp8x4x.c
> 
> diff --git a/arch/arm/boot/dts/pxa27x-lp8x4x.dts b/arch/arm/boot/dts/pxa27x-lp8x4x.dts
> index 872c386..07856e0 100644
> --- a/arch/arm/boot/dts/pxa27x-lp8x4x.dts
> +++ b/arch/arm/boot/dts/pxa27x-lp8x4x.dts
> @@ -161,6 +161,12 @@
>  				reg = <0x901c 0x1>;
>  				status = "okay";
>  			};
> +
> +			sram@a000 {
> +				compatible = "icpdas,sram-lp8x4x";
> +				reg = <0xa000 0x1000
> +				       0x901e 0x1>;
> +			};

You'll need a (trivial) DT binding doc in
Documentation/devicetree/bindings/ to go with this. You might also need
to split the arch/arm/boot/dts/ stuff out to a separate patch, so the
MTD driver can go in the MTD tree separate from the ARM tree bits.

>  		};
>  	};
>  };
> diff --git a/arch/arm/configs/lp8x4x_defconfig b/arch/arm/configs/lp8x4x_defconfig
> index d60e37a..17a4e6f 100644
> --- a/arch/arm/configs/lp8x4x_defconfig
> +++ b/arch/arm/configs/lp8x4x_defconfig
> @@ -57,6 +57,7 @@ CONFIG_MTD_CFI_ADV_OPTIONS=y
>  CONFIG_MTD_CFI_GEOMETRY=y
>  CONFIG_MTD_CFI_INTELEXT=y
>  CONFIG_MTD_PHYSMAP_OF=y
> +CONFIG_MTD_SRAM_LP8X4X=y
>  CONFIG_PROC_DEVICETREE=y
>  CONFIG_BLK_DEV_LOOP=y
>  CONFIG_BLK_DEV_LOOP_MIN_COUNT=2
> diff --git a/drivers/mtd/devices/Kconfig b/drivers/mtd/devices/Kconfig
> index 0128138..95f2075 100644
> --- a/drivers/mtd/devices/Kconfig
> +++ b/drivers/mtd/devices/Kconfig
> @@ -217,4 +217,18 @@ config BCH_CONST_T
>  	default 4
>  endif
>  
> +config MTD_SRAM_LP8X4X
> +	tristate "SRAM on ICPDAS LP-8X4X"
> +	depends on OF && ARCH_PXA
> +       ---help---
> +	 This provides an MTD device driver for 512kiB of battery backed up SRAM
> +	 on ICPDAS LP-8X4X programmable automation controllers.
> +
> +	 SRAM chip is connected via FPGA and is not accessible without a driver,
> +	 unlike flash memory which is wired to CPU MMU.
> +
> +	 Say N, unless you plan to run this kernel on LP-8X4X.
> +
> +	 If you say M, the module will be called sram_lp8x4x.
> +
>  endmenu
> diff --git a/drivers/mtd/devices/Makefile b/drivers/mtd/devices/Makefile
> index d83bd73..56a74c9 100644
> --- a/drivers/mtd/devices/Makefile
> +++ b/drivers/mtd/devices/Makefile
> @@ -16,6 +16,7 @@ obj-$(CONFIG_MTD_NAND_OMAP_BCH)	+= elm.o
>  obj-$(CONFIG_MTD_SPEAR_SMI)	+= spear_smi.o
>  obj-$(CONFIG_MTD_SST25L)	+= sst25l.o
>  obj-$(CONFIG_MTD_BCM47XXSFLASH)	+= bcm47xxsflash.o
> +obj-$(CONFIG_MTD_SRAM_LP8X4X)	+= sram_lp8x4x.o
>  
>  
>  CFLAGS_docg3.o			+= -I$(src)
> diff --git a/drivers/mtd/devices/sram_lp8x4x.c b/drivers/mtd/devices/sram_lp8x4x.c
> new file mode 100644
> index 0000000..9dc7149
> --- /dev/null
> +++ b/drivers/mtd/devices/sram_lp8x4x.c
> @@ -0,0 +1,227 @@
> +/*
> + *  linux/drivers/mtd/devices/lp8x4x_sram.c
> + *
> + *  MTD Driver for SRAM on ICPDAS LP-8x4x
> + *  Copyright (C) 2013 Sergei Ianovich <ynvich@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 or any later version.
> + */
> +
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/mtd/map.h>
> +#include <linux/mtd/mtd.h>
> +#include <linux/mtd/partitions.h>
> +#include <linux/platform_device.h>
> +#include <linux/of_device.h>
> +#include <linux/slab.h>
> +#include <linux/string_helpers.h>
> +#include <linux/types.h>
> +
> +#include <asm/mach/flash.h>

Do you need this? It looks unused.

> +
> +struct lp8x4x_sram_info {
> +	void __iomem	*bank;
> +	void __iomem	*virt;
> +	struct mutex	lock;
> +	unsigned	active_bank;
> +	struct mtd_info	mtd;
> +};
> +
> +static int
> +lp8x4x_sram_erase(struct mtd_info *mtd, struct erase_info *instr)
> +{
> +	struct lp8x4x_sram_info *info = mtd->priv;
> +	unsigned bank = instr->addr >> 11;
> +	unsigned offset = (instr->addr & 0x7ff) << 1;
> +	loff_t i;
> +
> +	mutex_lock(&info->lock);
> +	if (unlikely(bank != info->active_bank)) {
> +		info->active_bank = bank;
> +		iowrite8(bank, info->bank);
> +	}
> +	for (i = 0; i < instr->len; i++) {
> +		iowrite8(0xff, info->virt + offset);
> +		offset += 2;
> +		if (unlikely(offset == 0)) {
> +			info->active_bank++;
> +			iowrite8(info->active_bank, info->bank);
> +		}
> +	}
> +	mutex_unlock(&info->lock);
> +	instr->state = MTD_ERASE_DONE;
> +	mtd_erase_callback(instr);
> +
> +	return 0;
> +}
> +
> +static int
> +lp8x4x_sram_write(struct mtd_info *mtd, loff_t to, size_t len,
> +		size_t *retlen, const u_char *b)
> +{
> +	struct lp8x4x_sram_info *info = mtd->priv;
> +	unsigned bank = to >> 11;
> +	unsigned offset = (to & 0x7ff) << 1;
> +	loff_t i;
> +
> +	mutex_lock(&info->lock);
> +	if (unlikely(bank != info->active_bank)) {
> +		info->active_bank = bank;
> +		iowrite8(bank, info->bank);
> +	}
> +	for (i = 0; i < len; i++) {
> +		iowrite8(b[i], info->virt + offset);
> +		offset += 2;
> +		if (unlikely(offset == 0)) {
> +			info->active_bank++;
> +			iowrite8(info->active_bank, info->bank);
> +		}
> +	}
> +	mutex_unlock(&info->lock);
> +	*retlen = len;
> +	return 0;
> +}
> +
> +static int
> +lp8x4x_sram_read(struct mtd_info *mtd, loff_t from, size_t len,
> +		size_t *retlen, u_char *b)
> +{
> +	struct lp8x4x_sram_info *info = mtd->priv;
> +	unsigned bank = from >> 11;
> +	unsigned offset = (from & 0x7ff) << 1;
> +	loff_t i;
> +
> +	mutex_lock(&info->lock);
> +	if (unlikely(bank != info->active_bank)) {
> +		info->active_bank = bank;
> +		iowrite8(bank, info->bank);
> +	}
> +	for (i = 0; i < len; i++) {
> +		b[i] = ioread8(info->virt + offset);
> +		offset += 2;
> +		if (unlikely(offset == 0)) {
> +			info->active_bank++;
> +			iowrite8(info->active_bank, info->bank);
> +		}
> +	}
> +	mutex_unlock(&info->lock);
> +	*retlen = len;
> +	return 0;
> +}
> +
> +static void
> +lp8x4x_sram_sync(struct mtd_info *mtd)
> +{
> +}

You don't need the empty call-back. See mtd_sync(), which only calls the
_sync callback if it's filled in.

> +
> +static struct of_device_id of_flash_match[] = {
> +	{
> +		.compatible	= "icpdas,sram-lp8x4x",
> +	},
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, of_flash_match);
> +
> +static const char * const probe_types[] = {
> +	"cmdlinepart", "RedBoot", "ofpart", "ofoldpart", NULL };

Please drop 'ofoldpart'; it is obsolte. And do you really want
'RedBoot'?

> +
> +static int
> +lp8x4x_sram_probe(struct platform_device *pdev)
> +{
> +	const struct of_device_id *match;
> +	struct lp8x4x_sram_info *info;
> +	struct resource *r1, *r2;
> +	char sz_str[16];
> +	struct mtd_part_parser_data ppdata;
> +	int err = 0;
> +
> +	match = of_match_device(of_flash_match, &pdev->dev);
> +	if (!match)
> +		return -EINVAL;
> +
> +	r1 = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	r2 = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> +	if (!r1 || !r2)
> +		return -ENODEV;

Move these next to the devm_ioremap_resource(), and then remove the
	if (!r1 || !r2)
checks, since devm_ioremap_resource() does them for you. (See
lib/devres.c.)

> +
> +	info = devm_kzalloc(&pdev->dev, sizeof(*info), GFP_KERNEL);
> +	if (!info)
> +		return -ENOMEM;
> +
> +	info->virt =  devm_ioremap_resource(&pdev->dev, r1);
> +	if (!info->virt) {
> +		dev_err(&pdev->dev, "Failed to ioremap %p\n",
> +		       info->virt);

You don't need the print message. devm_ioremap_resource() handles this
for you.

> +		return -EFAULT;
> +	}
> +
> +	info->bank = devm_ioremap_resource(&pdev->dev, r2);
> +	if (!info->bank) {
> +		dev_err(&pdev->dev, "Failed to ioremap %p\n",
> +		       info->bank);

Ditto.

> +		return -EFAULT;
> +	}
> +
> +	info->mtd.priv = info;
> +	info->mtd.name = "SRAM";
> +	info->mtd.type = MTD_RAM;
> +	info->mtd.flags = MTD_CAP_RAM;
> +	info->mtd.size = resource_size(r1) << 7;
> +	info->mtd.erasesize = 512;
> +	info->mtd.writesize = 4;
> +	info->mtd._erase = lp8x4x_sram_erase;
> +	info->mtd._write = lp8x4x_sram_write;
> +	info->mtd._read = lp8x4x_sram_read;
> +	info->mtd._sync = lp8x4x_sram_sync;
> +	info->mtd.owner = THIS_MODULE;
> +
> +	mutex_init(&info->lock);
> +	iowrite8(info->active_bank, info->bank);
> +	platform_set_drvdata(pdev, info);
> +
> +	ppdata.of_node = pdev->dev.of_node;
> +	err = mtd_device_parse_register(&info->mtd, probe_types, &ppdata,
> +			NULL, 0);

If you don't need the other partition types (commented above), then you
can just use the defaults (drivers/mtd/mtdpart.c,
default_mtd_part_types) by dropping your 'probe_types' and making the
second argument NULL.

> +
> +	if (err < 0) {
> +		dev_err(&pdev->dev, "Failed to register platform device\n");

How about "failed to register MTD"?

> +		return err;
> +	}
> +
> +	string_get_size(info->mtd.size, STRING_UNITS_2, sz_str,
> +			sizeof(sz_str));
> +	dev_info(&pdev->dev, "using %s SRAM on LP-8X4X as %s\n", sz_str,
> +			dev_name(&info->mtd.dev));
> +	return 0;
> +}
> +
> +static int
> +lp8x4x_sram_remove(struct platform_device *dev)
> +{
> +	struct lp8x4x_sram_info *info = platform_get_drvdata(dev);
> +
> +	mtd_device_unregister(&info->mtd);

Please check the return code.

> +	platform_set_drvdata(dev, NULL);

I don't think you need to do this any more. The driver core takes care
of this on removal.

> +	return 0;

(So just: return mtd_device_unregister(&info->mtd);)

> +}
> +
> +static struct platform_driver lp8x4x_sram_driver = {
> +	.driver = {
> +		.name		= "sram-lp8x4x",
> +		.owner		= THIS_MODULE,
> +		.of_match_table = of_flash_match,
> +	},
> +	.probe		= lp8x4x_sram_probe,
> +	.remove		= lp8x4x_sram_remove,
> +};
> +
> +module_platform_driver(lp8x4x_sram_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Sergei Ianovich <ynvich@gmail.com>");
> +MODULE_DESCRIPTION("MTD driver for SRAM on ICPDAS LP-8x4x");

With that, you have my:

	Reviewed-by: Brian Norris <computersforpeace@gmail.com>

and I can merge this to the MTD tree if/when you'd like.

Brian

On Tue, 2014-04-15 at 22:04 -0700, Brian Norris wrote:
> Hi Sergei,
> 
> On Tue, Dec 17, 2013 at 11:37:40PM +0400, Sergei Ianovich wrote:
> > This provides an MTD device driver for 512kB of battery backed up SRAM
> > on ICPDAS LP-8X4X programmable automation controllers.
> > 
> > SRAM chip is connected via FPGA and is not accessible without a driver,
> > unlike flash memory which is wired to CPU MMU.
> > 
> > This SRAM becomes an excellent persisent storage of volatile process
> > data like counter values and sensor statuses. Storing those data in
> > flash or mmc card is not a viable solution.
> > 
> > Signed-off-by: Sergei Ianovich <ynvich@gmail.com>
> > ---
> >    v2..v3
> >    * no changes (except number 08/16 -> 10/21)
> > 
> >    v0..v2
> >    * use device tree
> >    * use devm helpers where possible
> 
> What's the status of this series? Is the rest of this platform support
> going in via other trees yet? I have a few trivial comments, but this
> driver mostly looks good as-is.

(...)

> You'll need a (trivial) DT binding doc in
> Documentation/devicetree/bindings/ to go with this. You might also need
> to split the arch/arm/boot/dts/ stuff out to a separate patch, so the
> MTD driver can go in the MTD tree separate from the ARM tree bits.

(...)

> With that, you have my:
> 
> 	Reviewed-by: Brian Norris <computersforpeace@gmail.com>
> 
> and I can merge this to the MTD tree if/when you'd like.

Thanks for response, the rest of the series is stuck on a DMA driver
with no development activity. I'll fix the comments, separate ARM staff
and refile the patch.