linux-kernel - Re: [PATCH 1/2] mtd: spi-nor: introduce SNOR

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Message-ID: <7365146d-b001-2a14-014d-62a6b19f4381@microchip.com>
Date:   Tue, 19 Jul 2022 07:33:26 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <michael@...le.cc>
CC:     <p.yadav@...com>, <miquel.raynal@...tlin.com>, <richard@....at>,
        <vigneshr@...com>, <linux-mtd@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] mtd: spi-nor: introduce SNOR_ID3()

On 7/19/22 10:07, Michael Walle wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> Am 2022-07-19 07:57, schrieb Tudor.Ambarus@...rochip.com:
>> On 5/10/22 17:02, Michael Walle wrote:
>>> EXTERNAL EMAIL: Do not click links or open attachments unless you know
>>> the content is safe
>>>
>>> Up until now, flashes were defined by specifying the JEDEC ID, the
>>> sector size and the number of sectors. This can be read by parsing the
>>> SFDP, we don't have to specify it. Thus provide a new macro SNOR_ID3()
>>> which just takes the JEDEC ID and implicitly set .parse_sfdp = true.
>>> All
>>> new flashes which have SFDP should use this macro.
>>
>> I like the idea, but you need to refine it a bit.
>> Your assumptions are true only for flashes that are compliant with SFDP
>> revB or
>> later because params->page_size is initialized by querying BFPT DWORD
>> 11. I think it would be good to specify this in the comment section.
> 
> Sure.
> 
>> Also, I think you introduce
>> a bug in spi_nor_select_erase() when CONFIG_MTD_SPI_NOR_USE_4K_SECTORS
>> is not
>> selected. wanted_size will be zero, will you select an invalid erase
>> type?
> 
> You mean to squeeze [1] into this one? If so, sure.
> 
> -michael
> 
> [1]
> https://lore.kernel.org/linux-mtd/20220716000643.3541839-1-quic_jaehyoo@quicinc.com/

No, these are orthogonal. If you keep wanted_size to zero, then
spi_nor_select_uniform_erase() will return NULL, doesn't it?


Maybe to adapt the code to something like
diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 21cefe2864ba..dd6cd852d1ef 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -2148,7 +2148,7 @@ static int spi_nor_select_erase(struct spi_nor *nor)
        struct spi_nor_erase_map *map = &nor->params->erase_map;
        const struct spi_nor_erase_type *erase = NULL;
        struct mtd_info *mtd = &nor->mtd;
-       u32 wanted_size = nor->info->sector_size;
+       u32 wanted_size = nor->params->sector_size;

and fill nor->params->sector_size even when no SFDP

Also, params->size = (u64)info->sector_size * info->n_sectors; from
spi_nor_init_default_params() becomes superfluous. I would check
the fields that I don't initialize in flash_info with SNOR_ID3
and check how I can mitigate their absence throughout the code.