On Tue, 1 May 2018 05:01:23 +0000 "Wan, Jane (Nokia - US/Sunnyvale)" <jane....@nokia.com> wrote:
> Hi Miquèl and Boris, > > Thank you for your response and feedback. I've modified the fix based on > your comments. > Please see the updated patch file at the end of this message (also in > attachment). > My answers to your comments/questions are inline in the previous message. > > Here is the answer to Boris question in another email thread: > > > What if some NANDs have 4 or more copies of the param page? > [Jane] The ONFI spec defines that the parameter page and its two redundant > copies are mandatory. > The additional redundant pages are optional. Currently, the FSL NAND driver > only reads the first > parameter page. This patch is to fix the driver to meet the mandatory > requirement in the spec. > We got a batch of particularly bad NAND chips recently and we needed these > changes to make them > work reliably over temperature. The patch was verified using these bad chips. And that proves my point. The core is reading 3 param pages [1], but since this driver was trying to guess how many bytes to read from ->cmdfunc() and did not guess correctly you ended up with a partially working implementation (works only if the first PARAM page is valid). Now, you fix it to read 3 PARAM pages, but what if we decide to read more to cope with MLC NANDs where even more copy are needed to have one valid version? You'll have to patch ->cmdfunc() again, just because you're trying to guess something that the core is supposed to tell you. [1]https://elixir.bootlin.com/linux/v4.17-rc3/source/drivers/mtd/nand/raw/nand_base.c#L5115
