Am Freitag, den 26.10.2012, 12:17 -0400 schrieb Paul Gortmaker:

On Thu, Oct 18, 2012 at 10:27 AM, Philipp Zabel [off-list ref] wrote:

quoted

On some platforms the SRAM needs a clock to be enabled explicitly.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
---
 drivers/misc/sram.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
index 7a363f2..0cc2e75 100644
--- a/drivers/misc/sram.c
+++ b/drivers/misc/sram.c

@@ -21,6 +21,8 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/init.h>
+#include <linux/clk.h>
+#include <linux/err.h>
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>

@@ -29,6 +31,7 @@

 struct sram_dev {
        struct gen_pool *pool;
+       struct clk *clk;
 };

I see another field gets added to the struct here.  (yet another
reason to have it folded into the original)   But you still
really don't need to create a sram_dev for this, because...

quoted

 static int __devinit sram_probe(struct platform_device *pdev)

@@ -53,6 +56,10 @@ static int __devinit sram_probe(struct platform_device *pdev)
        if (!sram)
                return -ENOMEM;

+       sram->clk = devm_clk_get(&pdev->dev, NULL);
+       if (!IS_ERR(sram->clk))
+               clk_prepare_enable(sram->clk);
+
        sram->pool = gen_pool_create(PAGE_SHIFT, -1);
        if (!sram->pool)
                return -ENOMEM;

@@ -80,6 +87,9 @@ static int __devexit sram_remove(struct platform_device *pdev)

        gen_pool_destroy(sram->pool);

+       if (!IS_ERR(sram->clk))
+               clk_disable_unprepare(sram->clk);
+

...here, this looks confusing with the use of IS_ERR on
an entity that was not recently assigned to.

Right.
How about I set sram->clk = NULL in sram_probe if devm_clk_get returns
an error value?

Instead, just
put a "struct clk *clk;" on the stack and do the

   clk = devm_clk_get(&pdev->dev, NULL);

in both the init and the teardown.  Then the code will be
more readable.

Calling devm_clk_get on the same clock twice seems a bit weird.
I expect that eventually someone will want to disable clocks during
suspend, so I'd prefer to keep the clk pointer around.

regards
Philipp