[PATCH v3 4/6] mmc: pwrseq_simple: Add optional reference clock support

Javier Martinez Canillas
2015-01-29T15:00:06Z

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 <javier.martinez@collabora.co.uk>
---

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