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    Subject[PATCH 4.19 130/287] mmc: sdhci-of-at91: fix set_uhs_signaling rewriting of MC1R
    Date
    From: Eugen Hristev <eugen.hristev@microchip.com>

    [ Upstream commit 5987e6ded29d52e42fc7b06aa575c60a25eee38e ]

    In set_uhs_signaling, the DDR bit is being set by fully writing the MC1R
    register.
    This can lead to accidental erase of certain bits in this register.
    Avoid this by doing a read-modify-write operation.

    Fixes: d0918764c17b ("mmc: sdhci-of-at91: fix MMC_DDR_52 timing selection")
    Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
    Tested-by: Karl Olsen <karl@micro-technic.com>
    Acked-by: Adrian Hunter <adrian.hunter@intel.com>
    Link: https://lore.kernel.org/r/20220630090926.15061-1-eugen.hristev@microchip.com
    Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/mmc/host/sdhci-of-at91.c | 9 +++++++--
    1 file changed, 7 insertions(+), 2 deletions(-)

    diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
    index 8cd1794768ba..70ce977cfeec 100644
    --- a/drivers/mmc/host/sdhci-of-at91.c
    +++ b/drivers/mmc/host/sdhci-of-at91.c
    @@ -117,8 +117,13 @@ static void sdhci_at91_set_power(struct sdhci_host *host, unsigned char mode,
    static void sdhci_at91_set_uhs_signaling(struct sdhci_host *host,
    unsigned int timing)
    {
    - if (timing == MMC_TIMING_MMC_DDR52)
    - sdhci_writeb(host, SDMMC_MC1R_DDR, SDMMC_MC1R);
    + u8 mc1r;
    +
    + if (timing == MMC_TIMING_MMC_DDR52) {
    + mc1r = sdhci_readb(host, SDMMC_MC1R);
    + mc1r |= SDMMC_MC1R_DDR;
    + sdhci_writeb(host, mc1r, SDMMC_MC1R);
    + }
    sdhci_set_uhs_signaling(host, timing);
    }

    --
    2.35.1


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