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Date: Thu, 15 Nov 2018 11:46:20 +0100
From: Boris Brezillon <boris.brezillon@bootlin.com>
To: <Tudor.Ambarus@microchip.com>
Cc: <alexander.sverdlin@nokia.com>, <linux-mtd@lists.infradead.org>,
 <marek.vasut@gmail.com>, <dwmw2@infradead.org>,
 <computersforpeace@gmail.com>, <richard@nod.at>,
 <Cristian.Birsan@microchip.com>
Subject: Re: [RFC] mtd: spi-nor: add support to non-uniform SFDP SPI NOR
 flash memories
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On Wed, 14 Nov 2018 08:00:44 +0000
<Tudor.Ambarus@microchip.com> wrote:

> Hi, Alexander,
> 
> On 11/13/2018 06:58 PM, Sverdlin, Alexander (Nokia - DE/Ulm) wrote:
> > Hello Tudor and all,
> > 
> > first of all, thank you for your work on SFDP support in Linux!
> > 
> > Unfortunately, I'm debugging a regression caused by 5390a8df769ec
> > "mtd: spi-nor: add support to non-uniform SFDP SPI NOR flash memories"
> > in [out of tree] support for S25FS128S.
> > 
> > The culprit is the following part of your patch:
> > 
> > 	/*
> > 	 * 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?