Re: [PATCH v2 0/4] mmc: sdhci_am654: Fix DDR50 mode for cards without tuning support

[Adrian Hunter]

On 03/08/2026 16:47, Diogo Ivo (Schneider Electric) wrote:
> DDR50 mode is not required to support the tuning command CMD19 by the
> eMMC/SD specification, meaning that calibration may fail on cards that
> do not implement it. This series fixes four issues discovered when
> using such cards:
> 
>   - Patch 1 moves the tuning_loop counter from a persistent struct field
>     to a local variable, preventing failed tuning attempts from depleting
>     the retry budget across calls.
> 
>   - Patch 2 ensures the command/data line reset is always performed
>     after tuning, even on failure, preventing stale data in the
>     controller buffer.
> 
>   - Patch 3 clears the ITAPDLY enable and delay values on tuning
>     failure so that leftover calibration values do not interfere with
>     subsequent I/O.
> 
>   - Patch 4 falls back to the DT-provided itap delay value for DDR50
>     when tuning fails in this mode, making a best-effort attempt at a
>     known-good delay being programmed.
> 
> Together these changes make DDR50 functional on TI J721E SoCs with
> cards that lack CMD19 tuning support. This second version addresses
> all comments from Sashiko, which I found to be correct.
> 
> Signed-off-by: Diogo Ivo (Schneider Electric) <diogo.ivo@xxxxxxxxxxx>

For all 4:

Acked-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>

> ---
> Changes in v2:
> - Add new patch moving tuning_loop to a local variable (Patch 1)
> - Clear ITAPDLY array values alongside HW registers on tuning failure (Patch 3)
> - Save DT-provided itap delay values for DDR50 in dedicated variables
>   to preserve them across tuning cycles (Patch 4)
> - Link to v1: https://patch.msgid.link/20260729-am654-sdhci-v1-0-7568108e4b9a@xxxxxxxxxxx
> 
> ---
> Diogo Ivo (Schneider Electric) (4):
>       mmc: sdhci_am654: Move tuning_loop to local variable
>       mmc: sdhci_am654: Reset command and data lines on failed tuning
>       mmc: sdhci_am654: Clear ITAPDLY on tuning failure
>       mmc: sdhci_am654: Fallback to DT-provided itap delay on DDR50 tuning failure
> 
>  drivers/mmc/host/sdhci_am654.c | 42 +++++++++++++++++++++++++++---------------
>  1 file changed, 27 insertions(+), 15 deletions(-)
> ---
> base-commit: f932188d6b0b684ee8555c8ecf1cac3567c4b106
> change-id: 20260728-am654-sdhci-85094d458bae
> 
> Best regards,
> --  
> Diogo Ivo <diogo.ivo@xxxxxxxxxxx>
>