Re: [PATCH] mmc: sdhci-esdhc-imx: correct the fix of ERR004536

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On Thu, 28 Feb 2019 at 09:41, BOUGH CHEN <haibo.chen@xxxxxxx> wrote:
>
>
> > -----Original Message-----
> > From: Ulf Hansson [mailto:ulf.hansson@xxxxxxxxxx]
> > Sent: 2019年2月28日 16:25
> > To: BOUGH CHEN <haibo.chen@xxxxxxx>
> > Cc: adrian.hunter@xxxxxxxxx; Aisheng Dong <aisheng.dong@xxxxxxx>;
> > shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx;
> > festevam@xxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>;
> > linux-mmc@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx
> > Subject: Re: [PATCH] mmc: sdhci-esdhc-imx: correct the fix of ERR004536
> >
> > On Thu, 28 Feb 2019 at 09:01, BOUGH CHEN <haibo.chen@xxxxxxx> wrote:
> > >
> > > Commit 18094430d6b5 ("mmc: sdhci-esdhc-imx: add ADMA Length
> > Mismatch
> > > errata fix") involve the fix of ERR004536, but the fix is incorrect.
> > > Double confirm with IC, need to clear the bit 7 of register 0x6c
> > > rather than set this bit 7.
> > > Here is the definition of bit 7 of 0x6c:
> > >     0: enable the new IC fix for ERR004536
> > >     1: do not use the IC fix, keep the same as before
> > >
> > > Due to the reset value of this bit 7 is 0, ROM code and bootloader do
> > > not touch this bit 7, so here directly remove the operation of this
> > > bit 7, make sure the fix of ERR004536 can work.
> >
> > Well, rather than relying on the bootloader, let the kernel do the right thing.
> > That is, write a zero to the register bit rather than a one.
> >
> > Is the code doing that?
> >
>
> Yes, write a zero to the register bit is correct.
> Why I just remove the code rather than directly write 0 to this bit is because the register 0x6c should be invisible to software, and is not defined in reference manual. It is a register only open for IC to test.
> If you prefer to write a zero to the register bit, I can do that.

I think that would be more safe, so yes, please.

[...]

Kind regards
Uffe




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