The Ultra Secured Digital Host Controller (uSDHC), used in i.MX6 (and, probably, earlier i.MX series too), uses a separate Watermark Levels register, controlling the amount of data or space available when raising status bit or interrupt. The current driver is non-compliant to SDHCI Specification. This patch sets the watermark level for PIO mode accesses to default block size (128 words or 512 bytes), so that the i.MX uSDHC behavior will be consistent to generic SDHCI Specification. More description about the patch exists in the git commit message. Test case: A MMCplus 4GB card was not getting detected with PIO mode enabled on a SabreLite reference board due to errors while initializing the MMC card. (Temporary modifications were done in sdhci-esdhc-imx.c and the device tree for SabreLite to set the transfer mode to PIO mode instead of the default DMA mode). Here is a snippet of the errors seen in the test case: root@mx6q:/opt/ltp# [ 6623.022646] mmc1: Timeout waiting for hardware interrupt. [ 6623.028072] mmc1: Timeout while processing request [ 6623.032911] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.038707] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.044496] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.050282] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.056068] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.061854] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.067642] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.073428] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.079215] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.085000] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.090785] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.096571] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.102357] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.108143] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.113928] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.119714] mmc1: Error -110: (data) got interrupt 0x00000020 [ 6623.127632] mmc1: Error -110: (data) while processing CMD8 request [ 6623.134099] mmc1: Error -110: (data) while retrieving EXT_CSD [ 6623.140566] mmc1: Error 110: while card (re)initializing [ 6623.146115] mmc1: error -110 whilst initialising MMC card [ 6623.151529] mmc1: Error -110: while initializing MMC card The above failure is resolved with the patch integrated. Tested on a highly modified v3.14 kernel and the patch was deployed in a commercial consumer product. The patch was rebased on to the following baseline (untested on this baseline): https://git.kernel.org/pub/scm/linux/kernel/git/ulfh/mmc.git/commit/?h=next&id=300ad8992913025b4294d4fc37b6bfff4a8b7ad1 "Merge branch 'fixes' into next" on the "next" branch, based on kernel v4.16. Recommend that further MMC related testing is performed on recent kernels to confirm that the patch is worthwhile for the mainline kernel. Andrew Gabbasov (1): mmc: sdhci-esdhc-imx: Set maximum watermark levels for PIO access drivers/mmc/host/sdhci-esdhc-imx.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
