On 8/9/20 10:12 AM, Krzysztof Kozlowski wrote:
On Tue, Aug 04, 2020 at 11:40:07AM +0100, Lukasz Luba wrote:
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@xxxxxxxxxx>
---
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.
These are different locks. You cannot protect dmc->curr_rate with
devfreq->lock in one place and dmc-lock in other place. This won't
protect it.
There are different paths that framework goes and mainly they are
protected by the df->lock.
But I tend to agree, I will send a patch which adds some locking.
Regards,
Lukasz
