Messages in this thread | | | From | Lukasz Luba <> | Subject | Re: [RFC] memory: exynos5422-dmc: Document mutex scope | Date | Tue, 4 Aug 2020 11:40:07 +0100 |
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Hi Krzysztof,
On 7/24/20 7:08 PM, Krzysztof Kozlowski wrote: > Document scope of the mutex used by driver. > > Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org> > > --- > > It seems mutex was introduced to protect: > 1. setting actual frequency/voltage, > 2. dmc->curr_rate (in exynos5_dmc_get_cur_freq()). > > However dmc->curr_rate in exynos5_dmc_get_status() is not protected. Is > it a bug?
The callback get_dev_status() from devfreq->profile, which here is the exynos5_dmc_get_status() should be already called with devfreq->lock mutex hold, like e.g from simple_ondemand governor or directly using update_devfreq exported function: update_devfreq() ->get_target_freq() devfreq_update_stats() df->profile->get_dev_status()
The dmc->curr_rate is also used from sysfs interface from devfreq. The local dmc lock serializes also this use case (when the HW freq has changed but not set yet into curr_rate.
> --- > drivers/memory/samsung/exynos5422-dmc.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/memory/samsung/exynos5422-dmc.c b/drivers/memory/samsung/exynos5422-dmc.c > index 93e9c2429c0d..0388066a7d96 100644 > --- a/drivers/memory/samsung/exynos5422-dmc.c > +++ b/drivers/memory/samsung/exynos5422-dmc.c > @@ -114,6 +114,7 @@ struct exynos5_dmc { > void __iomem *base_drexi0; > void __iomem *base_drexi1; > struct regmap *clk_regmap; > + /* Protects curr_rate and frequency/voltage setting section */ > struct mutex lock; > unsigned long curr_rate; > unsigned long curr_volt; >
I assume this missing comment for the lock was required by some scripts. In this case LGTM:
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Regards, Lukasz
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