The Atmel sdhci device needs a new quirk. sdhci_set_clock set the Clock
Control Register to 0 before computing the new value and writing it.
It disables the internal clock which causes a reset mecanism. If we
write the new value before this reset mecanism is done, it will prevent
the stabilisation of the internal clock, so a delay is needed. This
delay is about 2-3 cycles of the base clock. To be safe, a 1 ms delay is
used.
Signed-off-by: Ludovic Desroches <ludovic.desroches@xxxxxxxxx>
---
Hi Ulf,
Can you take these patches as fixes? I thought it was better to introduce a
quirk instead of duplicating a part of the sdhci_set_clock function to
implement my own set_clock function.
Regards
drivers/mmc/host/sdhci.c | 2 ++
drivers/mmc/host/sdhci.h | 5 +++++
2 files changed, 7 insertions(+)
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 64b7fdb..fbc7efd 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1160,6 +1160,8 @@ void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
host->mmc->actual_clock = 0;
sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
+ if (host->quirks2 & SDHCI_QUIRK2_NEED_DELAY_AFTER_INT_CLK_RST)
+ mdelay(1);
if (clock == 0)
return;
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index 7c02ff4..9d4aa31 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -412,6 +412,11 @@ struct sdhci_host {
#define SDHCI_QUIRK2_ACMD23_BROKEN (1<<14)
/* Broken Clock divider zero in controller */
#define SDHCI_QUIRK2_CLOCK_DIV_ZERO_BROKEN (1<<15)
+/*
+ * When internal clock is disabled, a delay is needed before modifying the
+ * SD clock frequency or enabling back the internal clock.
+ */
+#define SDHCI_QUIRK2_NEED_DELAY_AFTER_INT_CLK_RST (1<<16)
int irq; /* Device IRQ */
void __iomem *ioaddr; /* Mapped address */
--
2.5.0
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