Some controllers have 2 clock sources instead of 1. The 2nd clock
is for the internal card detect logic and must be enabled/disabled
along with the main core clock for proper operation.
Signed-off-by: Chris Brandt <chris.brandt@xxxxxxxxxxx>
---
v4:
* add technical explanation within probe routine
v3:
* add more clarification to the commit log
v2:
* changed clk2 to clk_cd
* disable clk if clk_cd enable fails
* changed clock name from "carddetect" to "cd"
---
drivers/mmc/host/sh_mobile_sdhi.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)
diff --git a/drivers/mmc/host/sh_mobile_sdhi.c b/drivers/mmc/host/sh_mobile_sdhi.c
index 59db14b..360d922 100644
--- a/drivers/mmc/host/sh_mobile_sdhi.c
+++ b/drivers/mmc/host/sh_mobile_sdhi.c
@@ -143,6 +143,7 @@ MODULE_DEVICE_TABLE(of, sh_mobile_sdhi_of_match);
struct sh_mobile_sdhi {
struct clk *clk;
+ struct clk *clk_cd;
struct tmio_mmc_data mmc_data;
struct tmio_mmc_dma dma_priv;
struct pinctrl *pinctrl;
@@ -190,6 +191,12 @@ static int sh_mobile_sdhi_clk_enable(struct tmio_mmc_host *host)
if (ret < 0)
return ret;
+ ret = clk_prepare_enable(priv->clk_cd);
+ if (ret < 0) {
+ clk_disable_unprepare(priv->clk);
+ return ret;
+ }
+
/*
* The clock driver may not know what maximum frequency
* actually works, so it should be set with the max-frequency
@@ -255,6 +262,8 @@ static void sh_mobile_sdhi_clk_disable(struct tmio_mmc_host *host)
struct sh_mobile_sdhi *priv = host_to_priv(host);
clk_disable_unprepare(priv->clk);
+ if (priv->clk_cd)
+ clk_disable_unprepare(priv->clk_cd);
}
static int sh_mobile_sdhi_card_busy(struct mmc_host *mmc)
@@ -572,6 +581,21 @@ static int sh_mobile_sdhi_probe(struct platform_device *pdev)
goto eprobe;
}
+ /*
+ * Some controllers provide a 2nd clock just to run the internal card
+ * detection logic. Unfortunately, the existing driver architecture does
+ * not support a separation of clocks for runtime PM usage. When
+ * native hotplug is used, the tmio driver assumes that the core
+ * must continue to run for card detect to stay active, so we cannot
+ * disable it.
+ * Additionally, it is prohibited to supply a clock to the core but not
+ * to the card detect circuit. That leaves us with if separate clocks
+ * are presented, we must treat them both as virtually 1 clock.
+ */
+ priv->clk_cd = devm_clk_get(&pdev->dev, "cd");
+ if (IS_ERR(priv->clk_cd))
+ priv->clk_cd = NULL;
+
priv->pinctrl = devm_pinctrl_get(&pdev->dev);
if (!IS_ERR(priv->pinctrl)) {
priv->pins_default = pinctrl_lookup_state(priv->pinctrl,
--
2.10.1
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