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mmc: sdhci: Disable SD card clock before changing parameters

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Per the SD Host Controller Simplified Specification v4.20 §3.2.3, change
the SD card clock parameters only after first disabling the external card
clock. Doing this fixes a spurious clock pulse on Baytrail and Apollo Lake
SD controllers which otherwise breaks voltage switching with a specific
Swissbit SD card.

Signed-off-by: Kyle Roeschley <kyle.roeschley@ni.com>
Signed-off-by: Brad Mouring <brad.mouring@ni.com>
Signed-off-by: Erick Shepherd <erick.shepherd@ni.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20250211214645.469279-1-erick.shepherd@ni.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Erick Shepherd 2025-02-11 15:46:45 -06:00 committed by Ulf Hansson
parent 4e35c611ee
commit fb3bbc46c9
1 changed files with 7 additions and 2 deletions
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9
drivers/mmc/host/sdhci.c
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@ -2065,10 +2065,15 @@ void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
host->mmc->actual_clock = 0;
sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
if (clk & SDHCI_CLOCK_CARD_EN)
sdhci_writew(host, clk & ~SDHCI_CLOCK_CARD_EN,
SDHCI_CLOCK_CONTROL);
if (clock == 0)
if (clock == 0) {
sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
return;
}
clk = sdhci_calc_clk(host, clock, &host->mmc->actual_clock);
sdhci_enable_clk(host, clk);