Re: [PATCH v2 0/4] renesas_sdhi: fix hang when SCC loses its clock

From: Ulf Hansson <ulf.hansson@linaro.org>
To: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: "linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
	Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Subject: Re: [PATCH v2 0/4] renesas_sdhi: fix hang when SCC loses its clock
Date: Thu, 3 Sep 2020 10:10:20 +0200	[thread overview]
Message-ID: <CAPDyKFr=7W3BG-ZXcOAWs3j-5W=mm7WrhcgyTQi8h3HmWe6iYA@mail.gmail.com> (raw)
In-Reply-To: <20200901150250.26236-1-wsa+renesas@sang-engineering.com>

On Tue, 1 Sep 2020 at 17:03, Wolfram Sang
<wsa+renesas@sang-engineering.com> wrote:
>
> This again took a while since v1 because the issue was so hard to
> trigger. But I finally found a way to inject the flaw, so this series
> could be tested and it fixes the issue.
>
> Changes since v1:
>         * introduce a new flag to MMC core indicating any kind of tuning
>           not only retune
>         * use the new flag to keep SCC flag active
>         * new patch 4, minor cleanup to MMC core
>
> A branch including the DEBUG patch can be found here:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux.git renesas/sdhi/new_manual_calib-for-5.10
>
> If you revert patch 3, you should have the SCC hang during boot again.
> For the record, let me copy some findings I mentioned in another thread:
>
> ===
> Interesting news: The hang comes from a code path I would have not
> expected. It is not because of accessing an SCC register, it is this
> line from renesas_sdhi_set_clock() which causes the issue:
>
> 186         sd_ctrl_write16(host, CTL_SD_CARD_CLK_CTL, clk & CLK_CTL_DIV_MASK);
>
> I mean I can guess that the clock setting has something to do with the
> SCC, but I can't see the direct connection with the documentation I
> have.
> ===
>
> Tested on R-Car H3 ES2.0 and M3-N and patches based on mmc/next.
>
> Another hope this is gone for good now...
>
> Kind regards,
>
>    Wolfram
>
>
> Wolfram Sang (4):
>   mmc: core: when downgrading HS400, callback into drivers earlier
>   mmc: core: add a 'doing_init_tune' flag and a 'mmc_doing_tune' helper
>   mmc: renesas_sdhi: keep SCC clock active when tuning
>   mmc: core: simplify an expression
>
>  drivers/mmc/core/mmc.c               | 16 ++++++++++------
>  drivers/mmc/host/renesas_sdhi_core.c |  8 ++++++--
>  include/linux/mmc/host.h             |  6 ++++++
>  3 files changed, 22 insertions(+), 8 deletions(-)
>
> --
> 2.20.1
>

Applied for next, thanks!

Kind regards
Uffe