cc a couple more people
On 21/04/16 16:28, Adrian Hunter wrote:
> Hi
>
> The RPMB partition only allows certain commands. In particular,
> the tuning command (CMD21) is not allowed - refer JEDEC eMMC
> standard v5.1 section 6.2.2 Command restrictions.
>
> That means commands will begin failing if re-tuning is needed
> while switched to the RPMB partition.
>
> Here are 4 options to fix the problem:
>
>
> 1. The approach taken by this patch set:
>
> To avoid tuning for RPMB, switch to High Speed mode from HS200
> or HS400 mode if re-tuning has been enabled. And switch back
> when leaving RPMB.
>
> Advantages: Directly does what needs to be done.
>
> Disadvantages: Assumes the mode switching will work.
>
>
> 2. Same as 1 but disable the tuning modes by removing them from
> card->mmc_avail_type and doing a full mmc_reset().
>
> Advantages: Simpler to program
>
> Disadvantages: Doing a full reset is slower. Doing a full reset
> is not an expected consequence of accessing RPMB.
>
>
> 3. Simply disable re-tuning and attempt to recover from any errors.
>
> Disadvantages: Due to the interdependent nature of RPMB reads/writes
> it might not be possible to recover without returning an error to the
> RPMB user. Also it would be difficult to test if the recovery actually
> worked in all cases.
>
>
> 4. Do a partiton switch as part of re-tuning.
>
> Disadvantages: Makes re-tuning more complicated. Would require moving
> the control of partition switching into the core. CRC errors arising
> from the need to re-tune might break the interdependent nature of RPMB
> operations.
>
>
> As a final note, if a solution is found then we might be able to revert
> commit 4e93b9a6abc0 ("mmc: card: Don't access RPMB partitions for normal
> read/write").
>
>
> Adrian Hunter (3):
> mmc: mmc: Factor out mmc_hs200_to_hs()
> mmc: mmc: Factor out mmc_hs400_to_hs() and __mmc_hs_to_hs200()
> mmc: block: Fix tuning (by avoiding it) for RPMB
>
> drivers/mmc/card/block.c | 36 +++++++++++
> drivers/mmc/core/mmc.c | 156 ++++++++++++++++++++++++++++++++++++++++++-----
> include/linux/mmc/card.h | 2 +-
> include/linux/mmc/core.h | 3 +
> include/linux/mmc/host.h | 5 ++
> 5 files changed, 186 insertions(+), 16 deletions(-)
>
>
> Regards
> Adrian
>
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