Some WLAN chips attached to a SDIO interface, need a reference clock.

Since this is very common, extend the prseq_simple driver to support
an optional clock that is enabled prior the card power up procedure.

Note: the external clock is optional. Thus an error is not returned
if the clock is not found.

Signed-off-by: Javier Martinez Canillas <redacted>
---

Changes since v2:
 - Add a clk_enabled bool to struct mmc_pwrseq_simple to track clock
   gate/ungate since .power_off can be called prior to .pre_power_on.
   Suggested by Ulf Hansson.
 - clk_get() does not return -ENOSYS so don't check for that.
   Suggested by Ulf Hansson.

Changes since v1:
 - Rebase on top of latest changes.
 - Use IS_ERR() instead of checking for NULL to see if the clock exists.
---
 drivers/mmc/core/pwrseq_simple.c | 38 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 36 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/core/pwrseq_simple.c b/drivers/mmc/core/pwrseq_simple.c
index e53d3c7e059c..50d09d920430 100644
--- a/drivers/mmc/core/pwrseq_simple.c
+++ b/drivers/mmc/core/pwrseq_simple.c

@@ -7,6 +7,7 @@
  *
  *  Simple MMC power sequence management
  */
+#include <linux/clk.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/device.h>

@@ -20,6 +21,8 @@

 struct mmc_pwrseq_simple {
        struct mmc_pwrseq pwrseq;
+       bool clk_enabled;
+       struct clk *ext_clk;
        int nr_gpios;
        struct gpio_desc *reset_gpios[0];
 };

@@ -39,6 +42,11 @@ static void mmc_pwrseq_simple_pre_power_on(struct mmc_host *host)
        struct mmc_pwrseq_simple *pwrseq = container_of(host->pwrseq,
                                        struct mmc_pwrseq_simple, pwrseq);

+       if (!IS_ERR(pwrseq->ext_clk)) {

+               clk_prepare_enable(pwrseq->ext_clk);
+               pwrseq->clk_enabled = true;
+       }
+
        mmc_pwrseq_simple_set_gpios_value(pwrseq, 1);
 }

@@ -50,6 +58,19 @@ static void mmc_pwrseq_simple_post_power_on(struct mmc_host *host)
        mmc_pwrseq_simple_set_gpios_value(pwrseq, 0);
 }

+static void mmc_pwrseq_simple_power_off(struct mmc_host *host)
+{
+       struct mmc_pwrseq_simple *pwrseq = container_of(host->pwrseq,
+                                       struct mmc_pwrseq_simple, pwrseq);
+
+       mmc_pwrseq_simple_set_gpios_value(pwrseq, 1);
+
+       if (pwrseq->clk_enabled) {

+               clk_disable_unprepare(pwrseq->ext_clk);
+               pwrseq->clk_enabled = false;
+       }
+}
+
 static void mmc_pwrseq_simple_free(struct mmc_host *host)
 {
        struct mmc_pwrseq_simple *pwrseq = container_of(host->pwrseq,

@@ -60,6 +81,9 @@ static void mmc_pwrseq_simple_free(struct mmc_host *host)
                if (!IS_ERR(pwrseq->reset_gpios[i]))
                        gpiod_put(pwrseq->reset_gpios[i]);

+       if (!IS_ERR(pwrseq->ext_clk))
+               clk_put(pwrseq->ext_clk);
+
        kfree(pwrseq);
        host->pwrseq = NULL;
 }

@@ -67,7 +91,7 @@ static void mmc_pwrseq_simple_free(struct mmc_host *host)
 static struct mmc_pwrseq_ops mmc_pwrseq_simple_ops = {
        .pre_power_on = mmc_pwrseq_simple_pre_power_on,
        .post_power_on = mmc_pwrseq_simple_post_power_on,
-       .power_off = mmc_pwrseq_simple_pre_power_on,
+       .power_off = mmc_pwrseq_simple_power_off,
        .free = mmc_pwrseq_simple_free,
 };

@@ -85,6 +109,13 @@ int mmc_pwrseq_simple_alloc(struct mmc_host *host, struct device *dev)
        if (!pwrseq)
                return -ENOMEM;

+       pwrseq->ext_clk = clk_get(dev, "ext_clock");
+       if (IS_ERR(pwrseq->ext_clk) &&
+           PTR_ERR(pwrseq->ext_clk) != -ENOENT) {
+               ret = PTR_ERR(pwrseq->ext_clk);
+               goto free;
+       }
+
        for (i = 0; i < nr_gpios; i++) {
                pwrseq->reset_gpios[i] = gpiod_get_index(dev, "reset", i,
                                                         GPIOD_OUT_HIGH);

@@ -96,7 +127,7 @@ int mmc_pwrseq_simple_alloc(struct mmc_host *host, struct device *dev)
                        while (--i)
                                gpiod_put(pwrseq->reset_gpios[i]);

-                       goto free;
+                       goto clk_put;
                }
        }

@@ -105,6 +136,9 @@ int mmc_pwrseq_simple_alloc(struct mmc_host *host, struct device *dev)
        host->pwrseq = &pwrseq->pwrseq;

        return 0;
+clk_put:
+       if (!IS_ERR(pwrseq->ext_clk))
+               clk_put(pwrseq->ext_clk);
 free:
        kfree(pwrseq);
        return ret;
--

2.1.3