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

Message

Wolfram Sang Sept. 1, 2020, 3:02 p.m. UTC

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(-)

Comments

Yoshihiro Shimoda Sept. 2, 2020, 9:51 a.m. UTC | #1

Hello Wolfram-san,

> From: Wolfram Sang, Sent: Wednesday, September 2, 2020 12:03 AM
> 
> 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.
<snip>
> 
> Tested on R-Car H3 ES2.0 and M3-N and patches based on mmc/next.

Thank you for the patch!

Reviewed-by: Yoshihiro Shimoda <[e-mail]>

And, I tested this series on R-Car H3 ES3.0 and M3-W+. And,
I confirmed this series could fix the SCC hang issue. So,

Tested-by: Yoshihiro Shimoda <[e-mail]>

Best regards,
Yoshihiro Shimoda

Ulf Hansson Sept. 3, 2020, 8:10 a.m. UTC | #2

On Tue, 1 Sep 2020 at 17:03, Wolfram Sang
<[e-mail]> 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