Re: [RFC] mtd: spi-nor: add support to non-uniform SFDP SPI NOR flash memories

["Sverdlin, Alexander (Nokia - DE/Ulm)" <alexander.sverdlin@xxxxxxxxx>]

Hello Boris,

On 15/11/2018 11:46, Boris Brezillon wrote:
>>> 	/*
>>> 	 * For non-uniform SPI flash memory, set mtd->erasesize to the
>>> 	 * maximum erase sector size. No need to set nor->erase_opcode.
>>> 	 */
>>> 	for (i = SNOR_ERASE_TYPE_MAX - 1; i >= 0; i--) {
>>> 		if (map->erase_type[i].size) {
>>> 			erase = &map->erase_type[i];
>>> 			break;
>>> 		}
>>> 	}
>>>
>>> The problem in our case is, we have existing partitioning with 128k partitions
>>> (the Flash itself supports 256k and 64k erasesize, depending on configuration).
>>> The chip is configured for 64k erasesize, non-uniform mapping.
>>>
>>> The mapping itself is being detected correctly, but when it comes to the code
>>> snippet above, it selects the biggest erasesize from all sizes advertised in
>>> SFDP, including 256k, which is not applicable to the current configuration.  
>> The fix would be to save the supported erase types when parsing the SFDP SMPT
>> table and use those instead.
> Alexander, Tudor, can one of you work on such a fix?

non-uniform case is complicated because currently I don't see the way to tell
mtdpart.c about non-uniform maps from spi-nor.c.

But same problem applies even to uniform maps, I have a patch already which
searches for minimum erase size, not maximum, I just have not tested it...

-- 
Best regards,
Alexander Sverdlin.
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