Hi Tanmay, On Tue, Oct 21, 2025 at 01:45:26PM -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.
Actually a power cycle or reset is required to make sure SD card to work correctly. Some SD cards may work in your case, some SD cards might not work, without a power cycle or reset. Thanks, Peng > >Signed-off-by: Tanmay Kathpalia <[email protected]>
