[PATCH v2] Revert "mmc: sdhci-cadence: trigger tuning for SD HS mode on SD6HC (v6) PHY"

[Peng Fan]

On Sun, Jun 28, 2026 at 11:16:15PM -0700, Tanmay Kathpalia wrote:
>This reverts commit b42c67188c14 ("mmc: sdhci-cadence: trigger tuning
>for SD HS mode on SD6HC (v6) PHY").
>
>The reverted patch introduced several issues:
>
>1. Non-standard tuning trigger: The SD Physical Layer Specification
>   only mandates execute_tuning for SDR50 and SDR104 UHS-I modes.
>   Triggering tuning for SD High Speed mode is outside the spec and
>   is handled via a non-standard set_ios_post callback rather than
>   through the established SDHCI framework tuning path.
>
>2. Non-standard device tree property: The patch introduced a new
>   "cdns,sd-hs-tuning" DT property to opt into SD HS tuning. This
>   is not aligned with existing DT bindings and bypasses the standard
>   MMC capability negotiation mechanism.
>
>3. Incorrect tunable mode allowlist: The sdhci_cdns6_mode_is_tuned()
>   function includes SD_HS, UHS_SDR50, and MMC_HS_400_ES as tunable
>   modes. According to the Cadence SD6HC IP User Guide (section 7.5.2,
>   Figure 18), tuning is only required for UHS-I SDR104 (SD) and
>   HS200 (eMMC). SD High Speed, UHS-I SDR50, and DDR50 only require
>   a PHY settings update from the pre-calculation script, not the
>   tuning procedure. HS400 transitions through HS200 and reuses its
>   tuned DLL value with a partial settings update. HS400ES only
>   requires a plain settings update from the calculation script with
>   no dependency on HS200 tuning.
>
>4. Tuned state management outside the framework: The patch manually
>   tracks tuned DLL state (tuned_mode, tuned_dll_slave_ctrl) and
>   restores it across PHY reconfigurations. This duplicates
>   responsibility that belongs in the core MMC tuning framework and
>   adds unnecessary complexity to the driver.
>
>Reverting to realign the driver with the IP documentation and the SD
>Physical Layer Specification.
>
>Signed-off-by: Tanmay Kathpalia <tanmay.kathpalia at altera.com>

Applied.

Thanks
Peng