Thread (5 messages) 5 messages, 3 authors, 2015-10-13

[PATCH 1/2] mmc: sdhci: add quirk SDHCI_QUIRK2_NEED_DELAY_AFTER_INT_CLK_RST

From: Ulf Hansson <hidden>
Date: 2015-10-08 18:01:27
Also in: linux-mmc, lkml

+Russell

On 17 September 2015 at 10:16, Ludovic Desroches
[off-list ref] wrote:
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 <redacted>
---
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.
Hi Ludovic,

Sorry for the delay!

I have been thinking of how to address patches for sdhci that adds
more quirks/callbacks. To be honest, I am fed up with such patches as
I think it keeps the development of sdhci going in the wrong
direction.

Instead, I have been hoping for someone to have stab into turning
sdhci into a library as Russell King pointed out several times as
well.

Now, as my response too you had a big delay for these patches and
because it's a fix intended for the rc, I am going to apply patch1 and
patch2 anyway. Although, you and everybody else that contributes to
the sdhci development, please consider this as the *last* time for
adding quirks/callbacks, unless you have *very good* reasons.

Kind regards
Uffe
quoted hunk ↗ jump to hunk
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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