mmc: sdhci-of-at91: fix CALCR register being rewritten

commit dbdea70 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: 727d836 ("mmc: sdhci-of-at91: add DT property to enable calibration on full reset")
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Link: https://lore.kernel.org/r/20200527105659.142560-1-eugen.hristev@microchip.com
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/mmc/host/sdhci-of-at91.c

@@ -120,9 +120,12 @@ static void sdhci_at91_reset(struct sdhci_host *host, u8 mask)
  || 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 = {