[PATCH 5.6 149/161] mmc: sdhci-of-at91: fix CALCR register being rewritten

[Greg Kroah-Hartman]

From: Eugen Hristev <eugen.hristev@xxxxxxxxxxxxx>

commit dbdea70f71d672c12bc4454e7c258a8f78194d74 upstream.

When enabling calibration at reset, the CALCR register was completely
rewritten. This may cause certain bits being deleted unintentedly.
Fix by issuing a read-modify-write operation.

Fixes: 727d836a375a ("mmc: sdhci-of-at91: add DT property to enable calibration on full reset")
Signed-off-by: Eugen Hristev <eugen.hristev@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20200527105659.142560-1-eugen.hristev@xxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/mmc/host/sdhci-of-at91.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/mmc/host/sdhci-of-at91.c
+++ b/drivers/mmc/host/sdhci-of-at91.c
@@ -136,9 +136,12 @@ static void sdhci_at91_reset(struct sdhc
 	    || mmc_gpio_get_cd(host->mmc) >= 0)
 		sdhci_at91_set_force_card_detect(host);
 
-	if (priv->cal_always_on && (mask & SDHCI_RESET_ALL))
-		sdhci_writel(host, SDMMC_CALCR_ALWYSON | SDMMC_CALCR_EN,
+	if (priv->cal_always_on && (mask & SDHCI_RESET_ALL)) {
+		u32 calcr = sdhci_readl(host, SDMMC_CALCR);
+
+		sdhci_writel(host, calcr | SDMMC_CALCR_ALWYSON | SDMMC_CALCR_EN,
 			     SDMMC_CALCR);
+	}
 }
 
 static const struct sdhci_ops sdhci_at91_sama5d2_ops = {