[PATCH] mmc: sd: Handle UHS-I voltage signaling without power cycle

[Peng Fan (OSS)]

From: Peng Fan <peng.fan at nxp.com>


On Tue, 21 Oct 2025 13:45:26 -0700, Tanmay Kathpalia wrote:
> Some boards have SD card connectors where the power rail cannot be switched
> off by the driver. However there are various circumstances when a card
> might be re-initialized, such as after system resume, warm re-boot, or
> error handling. However, a UHS card will continue to use 1.8V signaling
> unless it is power cycled.
> 
> If the card has not been power cycled, it may still be using 1.8V
> signaling. According to the SD spec., the Bus Speed Mode (function group 1)
> bits 2 to 4 are zero if the card is initialized at 3.3V signal level. Thus
> they can be used to determine if the card has already switched to 1.8V
> signaling. Detect that situation and try to initialize a UHS-I (1.8V)
> transfer mode.
> 
> [...]

Applied to mmc/next, thanks!

[1/1] mmc: sd: Handle UHS-I voltage signaling without power cycle
      commit: a9797a8a057b408e9c26f69d5e1d651285bf81c0

Best regards,
-- 
Peng Fan <peng.fan at nxp.com>