linux-kernel - [PATCH AUTOSEL 4.4 40/44] mmc: sdhci: Fix incorrect switch to HS mode

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Message-Id: <20190922190103.4906-40-sashal@kernel.org>
Date:   Sun, 22 Sep 2019 15:00:58 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Al Cooper <alcooperx@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Sasha Levin <sashal@...nel.org>, linux-mmc@...r.kernel.org
Subject: [PATCH AUTOSEL 4.4 40/44] mmc: sdhci: Fix incorrect switch to HS mode

From: Al Cooper <alcooperx@...il.com>

[ Upstream commit c894e33ddc1910e14d6f2a2016f60ab613fd8b37 ]

When switching from any MMC speed mode that requires 1.8v
(HS200, HS400 and HS400ES) to High Speed (HS) mode, the system
ends up configured for SDR12 with a 50MHz clock which is an illegal
mode.

This happens because the SDHCI_CTRL_VDD_180 bit in the
SDHCI_HOST_CONTROL2 register is left set and when this bit is
set, the speed mode is controlled by the SDHCI_CTRL_UHS field
in the SDHCI_HOST_CONTROL2 register. The SDHCI_CTRL_UHS field
will end up being set to 0 (SDR12) by sdhci_set_uhs_signaling()
because there is no UHS mode being set.

The fix is to change sdhci_set_uhs_signaling() to set the
SDHCI_CTRL_UHS field to SDR25 (which is the same as HS) for
any switch to HS mode.

This was found on a new eMMC controller that does strict checking
of the speed mode and the corresponding clock rate. It caused the
switch to HS400 mode to fail because part of the sequence to switch
to HS400 requires a switch from HS200 to HS before going to HS400.

Suggested-by: Adrian Hunter <adrian.hunter@...el.com>
Signed-off-by: Al Cooper <alcooperx@...il.com>
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/mmc/host/sdhci.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 62d37d2ac557b..1d6dfde1104d1 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1452,7 +1452,9 @@ void sdhci_set_uhs_signaling(struct sdhci_host *host, unsigned timing)
 		ctrl_2 |= SDHCI_CTRL_UHS_SDR104;
 	else if (timing == MMC_TIMING_UHS_SDR12)
 		ctrl_2 |= SDHCI_CTRL_UHS_SDR12;
-	else if (timing == MMC_TIMING_UHS_SDR25)
+	else if (timing == MMC_TIMING_SD_HS ||
+		 timing == MMC_TIMING_MMC_HS ||
+		 timing == MMC_TIMING_UHS_SDR25)
 		ctrl_2 |= SDHCI_CTRL_UHS_SDR25;
 	else if (timing == MMC_TIMING_UHS_SDR50)
 		ctrl_2 |= SDHCI_CTRL_UHS_SDR50;
-- 
2.20.1