13022591351 opened a new pull request, #19502: URL: https://github.com/apache/nuttx/pull/19502
## Summary The MMC wide bus switch sequence breaks eMMC 4-bit operation on hosts that program the bus width in the SDIO widebus/clock callbacks (e.g. STM32H7): CMD6 is issued before the host switched to wide bus (the switch silently fails and all following transfers time out), and the transfer clock is only selected after the switch sequence (it never takes effect, leaving the bus at ID-mode ~400 kHz). Switch the host to wide bus before CMD6, select the MMC transfer clock before calling mmcsd_widebus(), and use CLOCK_MMC_TRANSFER_4BIT when wide bus operation is active (mirroring the SD path). ## Impact MMC/eMMC only. SD cards are unaffected; hosts whose widebus callback only records state are unaffected. ## Testing Custom STM32H743 board with eMMC: sd_bench sequential write ~4.1 MB/s, read ~6.3 MB/s (previously all data transfers timed out). -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
