Re: [PATCH] mtd: spi-nor: Fix SF MTDIDS when registering multiple MTDs with DM enabled

[Marek Vasut <marex@denx.de>]

On 9/15/21 6:23 AM, Heiko Schocher wrote:
> Hi Marek,
> 
> On 15.09.21 01:06, Marek Vasut wrote:
>> The flash->mtd.name used to be nor%d before, now it is the type of the
>> SPI NOR like e.g. mt25ql02g. It is possible to find plenty of examples
>> of the former in U-Boot configs by searching for MTDIDS.*nor.*spi, while
>> the later is ambiguous if there are multiple flashes of the same type in
>> the system and breaks existing environments.
>>
>> This does no longer get recognized when running 'mtdparts' for example:
>> CONFIG_MTDIDS_DEFAULT="nor0=47040000.spi.0"
>>
>> Fix this by setting the correct mtd.name to nor%d.
>>
>> Fixes: b7f060565e3 ("mtd: spi-nor: allow registering multiple MTDs when DM is enabled")
>> Signed-off-by: Marek Vasut <marex@denx.de>
>> Cc: Heiko Schocher <hs@denx.de>
>> Cc: Jagan Teki <jagan@amarulasolutions.com>
>> Cc: Marek Behún <marek.behun@nic.cz>
>> Cc: Miquel Raynal <miquel.raynal@bootlin.com>
>> Cc: Pali Rohár <pali@kernel.org>
>> Cc: Patrice Chotard <patrice.chotard@foss.st.com>
>> Cc: Patrick Delaunay <patrick.delaunay@st.com>
>> Cc: Priyanka Jain <priyanka.jain@nxp.com>
>> Cc: Simon Glass <sjg@chromium.org>
>> ---
>>   drivers/mtd/spi/sf_mtd.c | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> Seem fixes the same problem as Patrick already posted here:
> 
> https://patchwork.ozlabs.org/project/uboot/patch/20210913095742.v2.1.I73dae4b93f0587dc130e512e95a1f4794e0b0233@changeid/
> 
> I find your approach cleaner, so:
> 
> Acked-by: Heiko Schocher <hs@denx.de>
> 
> @Patrick: Could you test this patch please?

The option from Patrick does look more predictable, but looking at the 
old implementation of spi_flash_mtd_number(), that one handled even 
cases of parallel-nor and spi-nor (both using the nor%d) present on the 
same system. This:

   static int spi_flash_mtd_number(void)
   {
   #ifdef CONFIG_SYS_MAX_FLASH_BANKS
          return CONFIG_SYS_MAX_FLASH_BANKS;
   #else
          return 0;
   #endif
   }
   ...
   sprintf(sf_mtd_name, "nor%d", spi_flash_mtd_number());

The patch from Patrick does not, it does per-spi-nor-only counting using 
the dev_seq() there, which is more predictable, but local to spi-nor.

The MTD core has its own IDR counting, which is used by this patch and 
is global to the MTD core. That has two issues, one is that it is 
possibly too global and counts both nor%d and nand%d, which means it 
would fail on systems with both SPI NOR and regular NAND. The other is 
it is likely less predictable (what happens if the SPI NOR and parallel 
NOR gets probed in the reverse order ? I know it is unlikely, but it can 
happen in the future).

So I think we need a third option which I would suggest be based on the 
patch from Patrick, but which would take into account the other nor%d 
devices like parallel NOR flashes.

That would likely have to happen in the mtd core using some modified IDR 
counting. I think you might need to modify it such that you would pass 
in the prefix of the device (like 'nor') and then do per-prefix 
counting, with the special case that parallel NORs are counted first. 
Also, that would also have to consider probing of multiple SPI NORs in 
either order (say you have two, if you do 'sf probe 0:0 ; sf probe 0:1' 
vs. 'sf probe 0:1 ; sf probe 0:0'), and make sure they get enumerated 
with the same nor%d value either way, that might be where the dev_seq() 
would come in.