[PATCH] mmc: sdhci-of-esdhc: add workaround for pre divider initial value

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For eSDHC(version < 2.3), the pre divider only could divide base clock
by 2 at least. Add workaround for this to avoid unexpected issue.

Signed-off-by: Yangbo Lu <yangbo.lu@xxxxxxxxxxxxx>
---
 drivers/mmc/host/sdhci-of-esdhc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/mmc/host/sdhci-of-esdhc.c b/drivers/mmc/host/sdhci-of-esdhc.c
index 797be75..46edf2c 100644
--- a/drivers/mmc/host/sdhci-of-esdhc.c
+++ b/drivers/mmc/host/sdhci-of-esdhc.c
@@ -208,6 +208,12 @@ static void esdhc_of_set_clock(struct sdhci_host *host, unsigned int clock)
 	if (clock == 0)
 		return;
 
+	/* Workaround to start pre_div at 2 for VNN < VENDOR_V_23 */
+	temp = in_be32(host->ioaddr + SDHCI_SLOT_INT_STATUS);
+	temp = (temp & SDHCI_VENDOR_VER_MASK) >> SDHCI_VENDOR_VER_SHIFT;
+	if (temp < VENDOR_V_23)
+		pre_div = 2;
+
 	/* Workaround to reduce the clock frequency for p1010 esdhc */
 	if (of_find_compatible_node(NULL, NULL, "fsl,p1010-esdhc")) {
 		if (clock > 20000000)
-- 
2.1.0.27.g96db324

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