Re: [PATCH v4 07/16] PM / devfreq: tegra: Properly disable interrupts

Thierry Reding
2019-06-04T11:07:51Z

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On Thu, May 02, 2019 at 02:38:06AM +0300, Dmitry Osipenko wrote:
> There is no guarantee that interrupt handling isn't running in parallel
> with tegra_actmon_disable_interrupts(), hence it is necessary to protect
> DEV_CTRL register accesses and clear IRQ status with ACTMON's IRQ being
> disabled in the Interrupt Controller in order to ensure that device
> interrupt is indeed being disabled.
>
> Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> ---
> drivers/devfreq/tegra-devfreq.c | 21 +++++++++++++++------
> 1 file changed, 15 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
> index b65313fe3c2e..ce1eb97a2090 100644
> --- a/drivers/devfreq/tegra-devfreq.c
> +++ b/drivers/devfreq/tegra-devfreq.c
> @@ -171,6 +171,8 @@ struct tegra_devfreq {
> struct notifier_block rate_change_nb;
>
> struct tegra_devfreq_device devices[ARRAY_SIZE(actmon_device_configs)];
> +
> + int irq;

Interrupts are typically unsigned int.

> };
>
> struct tegra_actmon_emc_ratio {
> @@ -417,6 +419,8 @@ static void tegra_actmon_disable_interrupts(struct tegra_devfreq *tegra)
> u32 val;
> unsigned int i;
>
> + disable_irq(tegra->irq);
> +
> for (i = 0; i < ARRAY_SIZE(tegra->devices); i++) {
> dev = &tegra->devices[i];
>
> @@ -427,9 +431,14 @@ static void tegra_actmon_disable_interrupts(struct tegra_devfreq *tegra)
> val &= ~ACTMON_DEV_CTRL_CONSECUTIVE_ABOVE_WMARK_EN;
>
> device_writel(dev, val, ACTMON_DEV_CTRL);
> +
> + device_writel(dev, ACTMON_INTR_STATUS_CLEAR,
> + ACTMON_DEV_INTR_STATUS);
> }
>
> actmon_write_barrier(tegra);
> +
> + enable_irq(tegra->irq);

Why do we enable interrupts after this? Is there any use in having the
top-level interrupt enabled if nothing's going to generate an interrupt
anyway?

> }
>
> static void tegra_actmon_configure_device(struct tegra_devfreq *tegra,
> @@ -604,7 +613,6 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
> struct resource *res;
> unsigned int i;
> unsigned long rate;
> - int irq;
> int err;
>
> tegra = devm_kzalloc(&pdev->dev, sizeof(*tegra), GFP_KERNEL);
> @@ -673,15 +681,16 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
> dev_pm_opp_add(&pdev->dev, rate, 0);
> }
>
> - irq = platform_get_irq(pdev, 0);
> - if (irq < 0) {
> - dev_err(&pdev->dev, "Failed to get IRQ: %d\n", irq);
> - return irq;
> + tegra->irq = platform_get_irq(pdev, 0);
> + if (tegra->irq < 0) {
> + err = tegra->irq;
> + dev_err(&pdev->dev, "Failed to get IRQ: %d\n", err);
> + return err;
> }

This is very oddly written. tegra->irq should really be an unsigned int
since that's the standard type for interrupt numbers. But since you need
to be able to detect errors from platform_get_irq() it now becomes
natural to write this as:

err = platform_get_irq(pdev, 0);
if (err < 0) {
dev_err(...);
return err;
}

tegra->irq = err;

Two birds with one stone. I suppose this could be done in a follow-up
patch since it isn't practically wrong in your version, so either way:

Acked-by: Thierry Reding <treding@nvidia.com>

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