On Mon, 28 Apr 2014, Peter Ujfalusi wrote: > On 04/28/2014 01:36 PM, Lee Jones wrote: > >> In certain boards the source for the clk32k clock can be gated. In these > >> boards the clk32k clock can be provided to the driver and it is going to be > >> enabled/disabled when it is needed. > >> If the clk32k clock is not provided the driver will assume that it is always > >> running. > >> > >> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx> > >> --- > >> Documentation/devicetree/bindings/mfd/twl6040.txt | 2 ++ > >> drivers/mfd/twl6040.c | 10 ++++++++++ > >> include/linux/mfd/twl6040.h | 2 ++ > >> 3 files changed, 14 insertions(+) > >> > >> diff --git a/Documentation/devicetree/bindings/mfd/twl6040.txt b/Documentation/devicetree/bindings/mfd/twl6040.txt > >> index 0f5dd709d752..a41157b5d930 100644 > >> --- a/Documentation/devicetree/bindings/mfd/twl6040.txt > >> +++ b/Documentation/devicetree/bindings/mfd/twl6040.txt > >> @@ -19,6 +19,8 @@ Required properties: > >> > >> Optional properties, nodes: > >> - enable-active-high: To power on the twl6040 during boot. > >> +- clocks: phandle to the clk32k clock provider > >> +- clock-names: Must be "clk32k" > >> > >> Vibra functionality > >> Required properties: > >> diff --git a/drivers/mfd/twl6040.c b/drivers/mfd/twl6040.c > >> index 2e6504a8e1e3..12b314ea48dc 100644 > >> --- a/drivers/mfd/twl6040.c > >> +++ b/drivers/mfd/twl6040.c > >> @@ -291,6 +291,8 @@ int twl6040_power(struct twl6040 *twl6040, int on) > >> if (twl6040->power_count++) > >> goto out; > >> > >> + clk_prepare_enable(twl6040->clk32k); > >> + > >> /* Allow writes to the chip */ > >> regcache_cache_only(twl6040->regmap, false); > >> > >> @@ -346,6 +348,8 @@ int twl6040_power(struct twl6040 *twl6040, int on) > >> > >> twl6040->sysclk = 0; > >> twl6040->mclk = 0; > >> + > >> + clk_disable_unprepare(twl6040->clk32k); > >> } > >> > >> out: > >> @@ -644,6 +648,12 @@ static int twl6040_probe(struct i2c_client *client, > >> > >> i2c_set_clientdata(client, twl6040); > >> > >> + twl6040->clk32k = devm_clk_get(&client->dev, "clk32k"); > >> + if (IS_ERR(twl6040->clk32k)) { > >> + dev_info(&client->dev, "clk32k is not handled\n"); > >> + twl6040->clk32k = NULL; > > > > So what happens if you pass a NULL clk reference to clk_prepare_enable()? > > We have checks for !clk in all cases within the clk_* API. If we pass NULL, > nothing will happen and from the calling driver point of view it will look > like a success. > AFAIK this is the way to handle non esential/optional clocks without if()s in > the driver code around the clock handling. Okay, so long as those checks are there, we're all good. -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html