[PATCH 6/6] mmc: sdhci-brcmstb: Fix incorrect switch to HS mode

Al Cooper
2020-01-13T21:08:08Z

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.

This issue was previously fixed by commit c894e33ddc191 ("mmc: sdhci:
Fix incorrect switch to HS mode") and later removed by commit
07bcc411567c ("Revert \"mmc: sdhci: Fix incorrect switch to HS mode\"")
because it caused failures with some SD cards on AM65X systems. The
fix will now be done in a platform specific callback instead of
common sdhci code.

Signed-off-by: Al Cooper <alcooperx@gmail.com>
Suggested-by: Adrian Hunter <adrian.hunter@intel.com>
---
drivers/mmc/host/sdhci-brcmstb.c | 31 ++++++++++++++++++++++++++++++-
1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-brcmstb.c b/drivers/mmc/host/sdhci-brcmstb.c
index 2c4b6e7e3d9a..ad01f6451a95 100644
--- a/drivers/mmc/host/sdhci-brcmstb.c
+++ b/drivers/mmc/host/sdhci-brcmstb.c
@@ -65,6 +65,35 @@ static void sdhci_brcmstb_set_clock(struct sdhci_host *host, unsigned int clock)
sdhci_enable_clk(host, clk);
}

+static void sdhci_brcmstb_set_uhs_signaling(struct sdhci_host *host,
+ unsigned int timing)
+{
+ u16 ctrl_2;
+
+ dev_dbg(mmc_dev(host->mmc), "%s: Setting UHS signaling for %d timing\n",
+ __func__, timing);
+ ctrl_2 = sdhci_readw(host, SDHCI_HOST_CONTROL2);
+ /* Select Bus Speed Mode for host */
+ ctrl_2 &= ~SDHCI_CTRL_UHS_MASK;
+ if ((timing == MMC_TIMING_MMC_HS200) ||
+ (timing == MMC_TIMING_UHS_SDR104))
+ ctrl_2 |= SDHCI_CTRL_UHS_SDR104;
+ else if (timing == MMC_TIMING_UHS_SDR12)
+ ctrl_2 |= SDHCI_CTRL_UHS_SDR12;
+ 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;
+ else if ((timing == MMC_TIMING_UHS_DDR50) ||
+ (timing == MMC_TIMING_MMC_DDR52))
+ ctrl_2 |= SDHCI_CTRL_UHS_DDR50;
+ else if (timing == MMC_TIMING_MMC_HS400)
+ ctrl_2 |= SDHCI_CTRL_HS400; /* Non-standard */
+ sdhci_writew(host, ctrl_2, SDHCI_HOST_CONTROL2);
+}
+
static void sdhci_brcmstb_dumpregs(struct mmc_host *mmc)
{
sdhci_dumpregs(mmc_priv(mmc));
@@ -101,7 +130,7 @@ static struct sdhci_ops sdhci_brcmstb_ops_7216 = {
.set_clock = sdhci_brcmstb_set_clock,
.set_bus_width = sdhci_set_bus_width,
.reset = sdhci_reset,
- .set_uhs_signaling = sdhci_set_uhs_signaling,
+ .set_uhs_signaling = sdhci_brcmstb_set_uhs_signaling,
};

static struct brcmstb_match_priv match_priv_7425 = {
--
2.17.1