Re: [PATCH v2] mfd: qcom_rpm: handle message RAM clock

From: Bjorn Andersson
Date: Thu Aug 18 2016 - 20:50:06 EST


On Thu 18 Aug 11:40 PDT 2016, Linus Walleij wrote:

> The MSM8660, APQ8060, IPQ806x and MSM8960 have a GCC clock
> to the message RAM used by the RPM. This needs to be enabled
> for messages to pass through. This is a crude solution that
> simply prepare/enable at probe() and disable/unprepare
> at remove(). More elaborate PM is probably possible to
> add later.
>
> The construction uses IS_ERR() to gracefully handle the
> platforms that do not provide a message RAM clock. It will
> bail out of probe only if the clock is hitting a probe
> deferral situation.
>
> Of course this requires the proper device tree set-up:
>
> rpm: rpm@104000 {
> compatible = "qcom,rpm-msm8660";
> clocks = <&gcc RPM_MSG_RAM_H_CLK>;
> clock-names = "ram";
> ...
> };
>
> I have provided this in the MSM8660 device tree, and will
> provide patches for the other targets.
>
> Cc: Björn Andersson <bjorn.andersson@xxxxxxxxxx>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>

Acked-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>

Regards,
Bjorn

> ---
> ChangeLog v1->v2:
> - Exploit that a clk can be NULL and handled transparently
> by the clock framework, simplifying the code
> - Move clock disablement after the OF depopulation call
> ---
> drivers/mfd/qcom_rpm.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/drivers/mfd/qcom_rpm.c b/drivers/mfd/qcom_rpm.c
> index 2e44323455dd..315da71bde49 100644
> --- a/drivers/mfd/qcom_rpm.c
> +++ b/drivers/mfd/qcom_rpm.c
> @@ -21,6 +21,7 @@
> #include <linux/mfd/qcom_rpm.h>
> #include <linux/mfd/syscon.h>
> #include <linux/regmap.h>
> +#include <linux/clk.h>
>
> #include <dt-bindings/mfd/qcom-rpm.h>
>
> @@ -48,6 +49,7 @@ struct qcom_rpm {
> struct regmap *ipc_regmap;
> unsigned ipc_offset;
> unsigned ipc_bit;
> + struct clk *ramclk;
>
> struct completion ack;
> struct mutex lock;
> @@ -501,6 +503,20 @@ static int qcom_rpm_probe(struct platform_device *pdev)
> mutex_init(&rpm->lock);
> init_completion(&rpm->ack);
>
> + /* Enable message RAM clock */
> + rpm->ramclk = devm_clk_get(&pdev->dev, "ram");
> + if (IS_ERR(rpm->ramclk)) {
> + ret = PTR_ERR(rpm->ramclk);
> + if (ret == -EPROBE_DEFER)
> + return ret;
> + /*
> + * Fall through in all other cases, as the clock is
> + * optional. (Does not exist on all platforms.)
> + */
> + rpm->ramclk = NULL;
> + }
> + clk_prepare_enable(rpm->ramclk); /* Accepts NULL */
> +
> irq_ack = platform_get_irq_byname(pdev, "ack");
> if (irq_ack < 0) {
> dev_err(&pdev->dev, "required ack interrupt missing\n");
> @@ -620,7 +636,11 @@ static int qcom_rpm_probe(struct platform_device *pdev)
>
> static int qcom_rpm_remove(struct platform_device *pdev)
> {
> + struct qcom_rpm *rpm = dev_get_drvdata(&pdev->dev);
> +
> of_platform_depopulate(&pdev->dev);
> + clk_disable_unprepare(rpm->ramclk);
> +
> return 0;
> }
>
> --
> 2.7.4
>