linux-kernel - Re: [PATCH v2] mtd: spinand: add support for FORESEE F35SQA002G

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Message-ID: <87ttc5c7gj.fsf@bootlin.com>
Date: Mon, 18 Nov 2024 08:43:56 +0100
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Chuanhong Guo <gch981213@...il.com>
Cc: SkyLake Huang <SkyLake.Huang@...iatek.com>,
  "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
  "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
  "mmkurbanov@...utedevices.com" <mmkurbanov@...utedevices.com>,
  "kernel@...rdevices.ru" <kernel@...rdevices.ru>,  "d-gole@...com"
 <d-gole@...com>,  "dev@...herer.org" <dev@...herer.org>,
  "vigneshr@...com" <vigneshr@...com>,  "richard@....at" <richard@....at>
Subject: Re: [PATCH v2] mtd: spinand: add support for FORESEE F35SQA002G

Hello,

> Several SPI-MEM controller don't allow software controlled CS, or for some
> other reasons are unable to execute a longer spi-mem op.
> spi_mem_dirmap_write returns the actual request size it's able to make,
> and spinand_write_to_cache_op use a while loop to split one update_cache
> request into multiple ones.
>
> This only works using the Random Program Load instruction (84h/34h)
> which preserves the previous written data in the flash data cache.
> All current supported flashes are exclusively using 84h/34h as the command
> to write the page cache.
>
> Load Program Data(02h/32h) will clear the entire page cache. As a
> result, when a request is split as described above, the previous written
> data will be cleared, breaking the page cache writing procedure.
>
> We can change write_to_cache_op to use Load Program Data on the
> first request. If that doesn't finish writing, use Random Program Load
> on subsequent data loading.

Sounds reasonable indeed, feel free to send a patch.

Thanks,
Miquèl