linux-kernel - Re: [PATCH 5/7] mmc: meson-gx: avoid clock glitch when switching to DDR modes

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Message-ID: <5d65cc12e18f9a4b86c097fbade0cef91b3b5d9b.camel@baylibre.com>
Date:   Fri, 19 Apr 2019 10:53:18 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        linux-amlogic@...ts.infradead.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] mmc: meson-gx: avoid clock glitch when switching to
 DDR modes

On Thu, 2019-04-18 at 23:15 +0200, Jerome Brunet wrote:
> On Thu, 2019-04-18 at 22:53 +0200, Martin Blumenstingl wrote:
> > Hi Jerome,
> > 
> > On Thu, Apr 18, 2019 at 10:46 PM Jerome Brunet <jbrunet@...libre.com> wrote:
> > > On Thu, 2019-04-18 at 22:16 +0200, Martin Blumenstingl wrote:
> > > > Hi Jerome,
> > > > 
> > > > On Wed, Apr 17, 2019 at 10:44 PM Jerome Brunet <jbrunet@...libre.com> wrote:
> > > > > Activating DDR in the Amlogic mmc controller, among other things, will
> > > > > divide the output clock by 2. So by activating it with clock on, we are
> > > > > creating a glitch on the output.
> > > > > 
> > > > > Instead, let's deal with DDR when the clock output is off, when setting
> > > > > the clock.
> > > > > 
> > > > > Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
> > > > it seems that this patch breaks SD card on my Khadas VIM and Khadas VIM2.
> > > 
> > > The error I see in your logs is with eMMC and hs200, not SD card.
> > sorry, I should have been more clear that there are two errors:
> > eMMC, this is what I have been seeing for a while on my Khadas VIM2
> > (it's probably not related to this patch):
> >    mmc1: mmc_select_hs200 failed, error -84
> >    mmc1: error -84 whilst initialising MMC card
> 
> Following patches were also supposed to help the vim2. 
> ... something I tested numerous time on this particular board.
> 
> > however, then there's this other error:
> >    print_req_error: I/O error, dev mmcblk0, sector 0 flags 0
> >    Buffer I/O error on dev mmcblk0, logical block 0, async page read
> > as result of this the partition table cannot be read and my kernel
> > cannot find the rootfs.
> 
> I don't know what the problem is (probably some CRC error - you can check the log
> in interrupt for this) but I'm pretty sure it is not related to this patch.
> 
> I see in the log SD is indeed in HS mode, so not in any DDR mode.
> I also see that the SDIO fails as well. There something really weird, which can't
> be explained by this patch alone AFAICT.

Ok, I think I got it. It is indeed not linked to DDR, but a more trivial mistake.
It looks like a writel went AWOL during the final rebase (and after the test campaign).

in meson_mmc_set_ios, after:
val |= FIELD_PREP(CFG_BUS_WIDTH_MASK, bus_width);

Could you try adding
writel(val, host->regs + SD_EMMC_CFG);

Without this, the bus width is not changed, which explains why eMMC, SD and SDIO fail
on init.

Let me know if this helps.