[PATCH v3 0/2] mmc: sdhci-of-arasan: workaround for broken clocks

[PATCH v3 0/2] mmc: sdhci-of-arasan: workaround for broken clocks

[Helmut Grohne]

This patch series works around the internal clock indicating stability too
quickly to operate. It manifests itself as:

    mmc0: error -84 whilst initialising SD card

Changes since v2:
 * Ulf Hansson requested splitting the patch in accordance with
   Documentation/devicetree/bindings/submitting-patches.txt. Also update
   recipient list accordingly.
 * Added Acked-by from Adrian Hunter.

Helmut Grohne (2):
  dt-bindings: mmc: broken clock stable indicator on arasan controllers
  mmc: sdhci-of-arasan: Add quirk for unstable clocks

 Documentation/devicetree/bindings/mmc/arasan,sdhci.txt |  2 ++
 drivers/mmc/host/sdhci-of-arasan.c                     | 16 ++++++++++++++++
 2 files changed, 18 insertions(+)

-- 
2.11.0

[PATCH v3 1/2] dt-bindings: mmc: broken clock stable indicator on arasan controllers

[Helmut Grohne]

Some controllers immediately report that their internal clock is stable
after activating it even when the clock is not stable. When used in
conjunction with older/slower cards, this can result in:

    mmc0: error -84 whilst initialising SD card

This flag allows documenting and thus working around such a hardware
defect.

Signed-off-by: Helmut Grohne <h.grohne@intenta.de>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
---
 Documentation/devicetree/bindings/mmc/arasan,sdhci.txt | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt b/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
index 60481bfc3d31..28332b655d2e 100644
--- a/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
+++ b/Documentation/devicetree/bindings/mmc/arasan,sdhci.txt
@@ -39,6 +39,8 @@ Optional Properties:
   - xlnx,fails-without-test-cd: when present, the controller doesn't work when
     the CD line is not connected properly, and the line is not connected
     properly. Test mode can be used to force the controller to function.
+  - xlnx,int-clock-stable-broken: when present, the controller always reports
+    that the internal clock is stable even when it is not.
 
 Example:
 	sdhci@e0100000 {
-- 
2.11.0

[PATCH v3 2/2] mmc: sdhci-of-arasan: Add quirk for unstable clocks

[Helmut Grohne]

Some controllers immediately report SDHCI_CLOCK_INT_STABLE after
enabling the clock even when the clock is not stable. When used in
conjunction with older/slower cards, this can result in:

    mmc0: error -84 whilst initialising SD card

When the stable reporting is known to be broken, we simply wait for the
maximum stabilization period.

Signed-off-by: Helmut Grohne <h.grohne@intenta.de>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
---
 drivers/mmc/host/sdhci-of-arasan.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/mmc/host/sdhci-of-arasan.c b/drivers/mmc/host/sdhci-of-arasan.c
index e3332a522a5d..a40bcc27f187 100644
--- a/drivers/mmc/host/sdhci-of-arasan.c
+++ b/drivers/mmc/host/sdhci-of-arasan.c
@@ -102,6 +102,9 @@ struct sdhci_arasan_data {
 
 /* Controller does not have CD wired and will not function normally without */
 #define SDHCI_ARASAN_QUIRK_FORCE_CDTEST	BIT(0)
+/* Controller immediately reports SDHCI_CLOCK_INT_STABLE after enabling the
+ * internal clock even when the clock isn't stable */
+#define SDHCI_ARASAN_QUIRK_CLOCK_UNSTABLE BIT(1)
 };
 
 static const struct sdhci_arasan_soc_ctl_map rk3399_soc_ctl_map = {
@@ -207,6 +210,16 @@ static void sdhci_arasan_set_clock(struct sdhci_host *host, unsigned int clock)
 
 	sdhci_set_clock(host, clock);
 
+	if (sdhci_arasan->quirks & SDHCI_ARASAN_QUIRK_CLOCK_UNSTABLE)
+		/*
+		 * Some controllers immediately report SDHCI_CLOCK_INT_STABLE
+		 * after enabling the clock even though the clock is not
+		 * stable. Trying to use a clock without waiting here results
+		 * in EILSEQ while detecting some older/slower cards. The
+		 * chosen delay is the maximum delay from sdhci_set_clock.
+		 */
+		msleep(20);
+
 	if (ctrl_phy) {
 		phy_power_on(sdhci_arasan->phy);
 		sdhci_arasan->is_phy_on = true;
@@ -758,6 +771,9 @@ static int sdhci_arasan_probe(struct platform_device *pdev)
 	if (of_property_read_bool(np, "xlnx,fails-without-test-cd"))
 		sdhci_arasan->quirks |= SDHCI_ARASAN_QUIRK_FORCE_CDTEST;
 
+	if (of_property_read_bool(np, "xlnx,int-clock-stable-broken"))
+		sdhci_arasan->quirks |= SDHCI_ARASAN_QUIRK_CLOCK_UNSTABLE;
+
 	pltfm_host->clk = clk_xin;
 
 	if (of_device_is_compatible(pdev->dev.of_node,
-- 
2.11.0

Re: [PATCH v3 1/2] dt-bindings: mmc: broken clock stable indicator on arasan controllers

[Rob Herring]

On Wed, Jun 20, 2018 at 01:32:51PM +0200, Helmut Grohne wrote:
> Some controllers immediately report that their internal clock is stable
> after activating it even when the clock is not stable. When used in
> conjunction with older/slower cards, this can result in:
> 
>     mmc0: error -84 whilst initialising SD card
> 
> This flag allows documenting and thus working around such a hardware
> defect.
> 
> Signed-off-by: Helmut Grohne <h.grohne@intenta.de>
> Acked-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
>  Documentation/devicetree/bindings/mmc/arasan,sdhci.txt | 2 ++
>  1 file changed, 2 insertions(+)

Reviewed-by: Rob Herring <robh@kernel.org>

Re: [PATCH v3 0/2] mmc: sdhci-of-arasan: workaround for broken clocks

[Ulf Hansson]

On 20 June 2018 at 13:32, Helmut Grohne <h.grohne@intenta.de> wrote:
> This patch series works around the internal clock indicating stability too
> quickly to operate. It manifests itself as:
>
>     mmc0: error -84 whilst initialising SD card
>
> Changes since v2:
>  * Ulf Hansson requested splitting the patch in accordance with
>    Documentation/devicetree/bindings/submitting-patches.txt. Also update
>    recipient list accordingly.
>  * Added Acked-by from Adrian Hunter.
>
> Helmut Grohne (2):
>   dt-bindings: mmc: broken clock stable indicator on arasan controllers
>   mmc: sdhci-of-arasan: Add quirk for unstable clocks
>
>  Documentation/devicetree/bindings/mmc/arasan,sdhci.txt |  2 ++
>  drivers/mmc/host/sdhci-of-arasan.c                     | 16 ++++++++++++++++
>  2 files changed, 18 insertions(+)
>
> --
> 2.11.0
>

Thanks, applied for next!

Kind regards
Uffe