Subject: Re: [PATCH v3] mtd: rawnand: ams-delta: Drop board specific partition info

From: Janusz Krzysztofik <[email-masked]>
Date: Thu, 25 Apr 2019 20:42:22 +0200

Hi Ladislav,

On Thursday, April 25, 2019 12:14:28 AM CEST Ladislav Michl wrote:
> Hi Janusz,
> 
> On Wed, Apr 24, 2019 at 08:02:12PM +0200, Janusz Krzysztofik wrote:
> > After recent modifications, only a hardcoded partition info makes
> > the driver device specific.  Other than that, the driver uses GPIO
> > exclusively and can be used on any hardware.
> > 
> > Drop the partition info and use MTD partition parser with default list
> > of parser names instead.  For the OF parser to work correctly, pass
> > device of_node to mtd.
> > 
> > Amstrad Delta users should append the following partition info to their
> > kernel command line, possibly embedding it in CONFIG_CMDLINE:
> > 
> > mtdparts=ams-delta-nand:3584k(Kernel),256k(u-boot),256k(u-boot_params),\
> > 256k(Amstrad_LDR),27m(File_system),768k(PBL_reserved)
> 
> now, when driver is no longer Amstrad Delta specific, why would you want
> to have ams-delta-nand hardcoded on kernel cmdline? I'm assuming at some
> point this driver will become gpio-nand [*] or something like that and
> asking users to change their kernel cmdline twice is just unwise :)

Hmm, I have no idea of a good name for the driver if not "gpio-nand". Can you 
suggest one?
As a workaround, I can add a platform device id table to the driver with "ams-
delta-nand" as a supported device name in hope that survives possible future 
driver renaming.

> [*] btw, it is really shame gpio-nand name is already taken by driver
> living in drivers/mtd/nand/raw/gpio.c which is more likely gpio-mem-nand
> used by at least CompuLab CM-X255 and Picochip picoXcell.

I think the best approach would be to expose NAND data ports of those machines 
as GPIO ports, possibly reusing the "gpio-nand" driver code while creating a 
new GPIO driver for them if "basic-mmio-gpio" occurs inappropriate, and use 
the pure GPIO NAND driver on top.

> Otherwise your work on this driver is so amazing that I just spent
> couple of hours finding that phone and compiling some decent userspace
> for it :) Thank you!

I'm glad you like it :-)
Janusz

> 
> > For their convenience, that information is added to the board Kconfig
> > entry help text, as well as CONFIG_MTD_CMDLINE_PARTS symbol is selected
> > automatically from the board Kconfig entry if the NAND driver is also
> > selected.
> > 
> > Signed-off-by: Janusz Krzysztofik <[email-masked]>
> > Cc: Tony Lindgren <[email-masked]>
> > Cc: Aaro Koskinen <[email-masked]>
> > ---
> > Changelog:
> > v2->v3:
> > - add information on the requirement for passing partition info via
> >   kernel command line to the board Kconfig entry help text
> > v1->v2:
> > - fix a typo poitned out by Aaro - thanks!
> > - fix device_node not passed to OF parser via mtd_info
> > - commit message reworded and reformatted a bit for better readability
> > 
> >  arch/arm/mach-omap1/Kconfig      |  7 ++++++-
> >  drivers/mtd/nand/raw/ams-delta.c | 29 ++---------------------------
> >  2 files changed, 8 insertions(+), 28 deletions(-)
> > 
> > diff --git a/arch/arm/mach-omap1/Kconfig b/arch/arm/mach-omap1/Kconfig
> > index c4694f26b5c4..41a47d251cac 100644
> > --- a/arch/arm/mach-omap1/Kconfig
> > +++ b/arch/arm/mach-omap1/Kconfig
> > @@ -164,17 +164,22 @@ config MACH_NOKIA770
> >  	  have such a device.
> >  
> >  config MACH_AMS_DELTA
> > -	bool "Amstrad E3 (Delta)"
> > +	bool "Amstrad E3 (Delta) - see help for important information"
> >  	depends on ARCH_OMAP1 && ARCH_OMAP15XX
> >  	select FIQ
> >  	select GPIO_GENERIC_PLATFORM
> >  	select LEDS_GPIO_REGISTER
> >  	select REGULATOR
> >  	select REGULATOR_FIXED_VOLTAGE
> > +	select MTD_CMDLINE_PARTS if MTD_NAND_AMS_DELTA
> >  	help
> >  	  Support for the Amstrad E3 (codename Delta) videophone. Say Y 
here
> >  	  if you have such a device.
> >  
> > +	  If you are using built-in NAND, append the following partition
> > +	  info to kernel command line:
> > +	  mtdparts=ams-delta-nand:3584k(Kernel),256k(u-boot),256k(u-
boot_params),256k(Amstrad_LDR),27m(File_system),768k(PBL_reserved)
> > +
> >  config MACH_OMAP_GENERIC
> >  	bool "Generic OMAP board"
> >  	depends on ARCH_OMAP1 && (ARCH_OMAP15XX || ARCH_OMAP16XX)
> > diff --git a/drivers/mtd/nand/raw/ams-delta.c b/drivers/mtd/nand/raw/ams-
delta.c
> > index 8312182088c1..e0f09179bbda 100644
> > --- a/drivers/mtd/nand/raw/ams-delta.c
> > +++ b/drivers/mtd/nand/raw/ams-delta.c
> > @@ -41,31 +41,6 @@ struct ams_delta_nand {
> >  	bool			data_in;
> >  };
> >  
> > -/*
> > - * Define partitions for flash devices
> > - */
> > -
> > -static const struct mtd_partition partition_info[] = {
> > -	{ .name		= "Kernel",
> > -	  .offset	= 0,
> > -	  .size		= 3 * SZ_1M + SZ_512K },
> > -	{ .name		= "u-boot",
> > -	  .offset	= 3 * SZ_1M + SZ_512K,
> > -	  .size		= SZ_256K },
> > -	{ .name		= "u-boot params",
> > -	  .offset	= 3 * SZ_1M + SZ_512K + SZ_256K,
> > -	  .size		= SZ_256K },
> > -	{ .name		= "Amstrad LDR",
> > -	  .offset	= 4 * SZ_1M,
> > -	  .size		= SZ_256K },
> > -	{ .name		= "File system",
> > -	  .offset	= 4 * SZ_1M + 1 * SZ_256K,
> > -	  .size		= 27 * SZ_1M },
> > -	{ .name		= "PBL reserved",
> > -	  .offset	= 32 * SZ_1M - 3 * SZ_256K,
> > -	  .size		=  3 * SZ_256K },
> > -};
> > -
> >  static void ams_delta_write_commit(struct ams_delta_nand *priv)
> >  {
> >  	gpiod_set_value(priv->gpiod_nwe, 0);
> > @@ -238,6 +213,7 @@ static int ams_delta_init(struct platform_device 
*pdev)
> >  	mtd->dev.parent = &pdev->dev;
> >  
> >  	nand_set_controller_data(this, priv);
> > +	nand_set_flash_node(this, pdev->dev.of_node);
> >  
> >  	priv->gpiod_rdy = devm_gpiod_get_optional(&pdev->dev, "rdy", 
GPIOD_IN);
> >  	if (IS_ERR(priv->gpiod_rdy)) {
> > @@ -315,8 +291,7 @@ static int ams_delta_init(struct platform_device 
*pdev)
> >  		return err;
> >  
> >  	/* Register the partitions */
> > -	err = mtd_device_register(mtd, partition_info,
> > -				  ARRAY_SIZE(partition_info));
> > +	err = mtd_device_parse_register(mtd, NULL, NULL, NULL, 0);
> >  	if (err)
> >  		goto err_nand_cleanup;
> >  
> 

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