From 732e3b293ca3155106fb05e73188c367cab6f979 Mon Sep 17 00:00:00 2001 From: Paul Cercueil <paul@crapouillou.net> Date: Tue, 31 Jan 2023 21:02:28 +0000 Subject: [PATCH] mmc: jz4740: Work around bug on JZ4760(B) 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(+) diff --git a/drivers/mmc/host/jz4740_mmc.c b/drivers/mmc/host/jz4740_mmc.c index 3c59dec08c3b..8586447d4b4f 100644 --- a/drivers/mmc/host/jz4740_mmc.c +++ b/drivers/mmc/host/jz4740_mmc.c @@ -1038,6 +1038,16 @@ static int jz4740_mmc_probe(struct platform_device* pdev) 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;