RE: [PATCH] mmc: rpmb: do not force a retune before RPMB switch

[Avri Altman]

> 
> On 4/12/23 17:01, Jorge Ramirez-Ortiz wrote:
> > Requesting a retune before switching to the RPMB partition has been
> > observed to cause CRC errors on the RPMB reads (-EILSEQ).
> 
> There are still 2 concerns:
> 1) We don't really know the root cause.  Have you determined if here are
> CRC errors in the main partition also?
> 2) Forcing this on everyone
> 
> The original idea was that because re-tuning cannot be done in RPMB, the
> need to re-rune in RPMB could be avoided by always re-tuning before
> switching to RPMB and then switching straight back. IIRC re-tuning should
> guarantee at least 4MB more I/O without issue.
Performance is hardly an issue in the context of RPMB access - 
For most cases it’s a single frame.

Thanks,
Avri

> 
> The alternative to dropping re-tuning in this case could be to add a retry loop
> for MMC_DRV_OP_IOCTL_RPMB if the error is -EILSEQ
> 
> 
> >
> > Since RPMB reads can not be retried, the clients would be directly
> > affected by the errors.
> >
> > This commit disables the request prior to RPMB switching while
> > allowing the pause interface to still request a retune before the
> > pause for other use cases.
> >
> > This was verified with the sdhci-of-arasan driver (ZynqMP) configured
> > for HS200 using two separate eMMC cards (DG4064 and 064GB2). In both
> > cases, the error was easy to reproduce triggering every few tenths of
> > reads.
> >
> > Signed-off-by: Jorge Ramirez-Ortiz <jorge@xxxxxxxxxxxx>
> > ---
> >  drivers/mmc/core/block.c | 2 +-
> >  drivers/mmc/core/host.c  | 7 ++++---
> >  drivers/mmc/core/host.h  | 2 +-
> >  3 files changed, 6 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c index
> > f9a5cffa64b1..1d69078ad9b2 100644
> > --- a/drivers/mmc/core/block.c
> > +++ b/drivers/mmc/core/block.c
> > @@ -859,7 +859,7 @@ static int mmc_blk_part_switch_pre(struct
> mmc_card *card,
> >                       if (ret)
> >                               return ret;
> >               }
> > -             mmc_retune_pause(card->host);
> > +             mmc_retune_pause(card->host, false);
> >       }
> >
> >       return ret;
> > diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c index
> > 096093f7be00..a9b95aaa2235 100644
> > --- a/drivers/mmc/core/host.c
> > +++ b/drivers/mmc/core/host.c
> > @@ -119,13 +119,14 @@ void mmc_retune_enable(struct mmc_host
> *host)
> >
> >  /*
> >   * Pause re-tuning for a small set of operations.  The pause begins
> > after the
> > - * next command and after first doing re-tuning.
> > + * next command and, if retune is set, after first doing re-tuning.
> >   */
> > -void mmc_retune_pause(struct mmc_host *host)
> > +void mmc_retune_pause(struct mmc_host *host, bool retune)
> >  {
> >       if (!host->retune_paused) {
> >               host->retune_paused = 1;
> > -             mmc_retune_needed(host);
> > +             if (retune)
> > +                     mmc_retune_needed(host);
> 
> Better to just drop mmc_retune_needed(host);
> 
> >               mmc_retune_hold(host);
> 
> There is still a small chance that re-tuning is needed anyway in which case it
> will still be done.
> 
> >       }
> >  }
> > diff --git a/drivers/mmc/core/host.h b/drivers/mmc/core/host.h index
> > 48c4952512a5..321776b52270 100644
> > --- a/drivers/mmc/core/host.h
> > +++ b/drivers/mmc/core/host.h
> > @@ -18,7 +18,7 @@ void mmc_retune_disable(struct mmc_host *host);
> > void mmc_retune_hold(struct mmc_host *host);  void
> > mmc_retune_release(struct mmc_host *host);  int mmc_retune(struct
> > mmc_host *host); -void mmc_retune_pause(struct mmc_host *host);
> > +void mmc_retune_pause(struct mmc_host *host, bool retune);
> >  void mmc_retune_unpause(struct mmc_host *host);
> >
> >  static inline void mmc_retune_clear(struct mmc_host *host)