From: Paul Cercueil paul@crapouillou.net
commit 3f18c5046e633cc4bbad396b74c05d46d353033d upstream.
On JZ4760 and JZ4760B, SD cards fail to run if the maximum clock rate is set to 50 MHz, even though the controller officially does support it.
Until the actual bug is found and fixed, limit the maximum clock rate to 24 MHz.
Signed-off-by: Paul Cercueil paul@crapouillou.net Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20230131210229.68129-1-paul@crapouillou.net Signed-off-by: Ulf Hansson ulf.hansson@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/mmc/host/jz4740_mmc.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
--- a/drivers/mmc/host/jz4740_mmc.c +++ b/drivers/mmc/host/jz4740_mmc.c @@ -1038,6 +1038,16 @@ static int jz4740_mmc_probe(struct platf mmc->ops = &jz4740_mmc_ops; if (!mmc->f_max) mmc->f_max = JZ_MMC_CLK_RATE; + + /* + * There seems to be a problem with this driver on the JZ4760 and + * JZ4760B SoCs. There, when using the maximum rate supported (50 MHz), + * the communication fails with many SD cards. + * Until this bug is sorted out, limit the maximum rate to 24 MHz. + */ + if (host->version == JZ_MMC_JZ4760 && mmc->f_max > JZ_MMC_CLK_RATE) + mmc->f_max = JZ_MMC_CLK_RATE; + mmc->f_min = mmc->f_max / 128; mmc->ocr_avail = MMC_VDD_32_33 | MMC_VDD_33_34;