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Subject[PATCH] scsi: ufs: Make sure clk scaling happens only when hba is runtime ACTIVE
Date
If someone plays with the UFS clk scaling devfreq governor through sysfs,
ufshcd_devfreq_scale may be called even when hba is not runtime ACTIVE,
which can lead to unexpected error. We cannot just protect it by calling
pm_runtime_get_sync, because that may cause racing problem since hba
runtime suspend ops needs to suspend clk scaling. In order to fix it, call
pm_runtime_get_noresume and check hba's runtime status, then only proceed
if hba is runtime ACTIVE, otherwise just bail.

governor_store
devfreq_performance_handler
update_devfreq
devfreq_set_target
ufshcd_devfreq_target
ufshcd_devfreq_scale

Signed-off-by: Can Guo <cang@codeaurora.org>

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index e4cb994..847f355 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1294,8 +1294,15 @@ static int ufshcd_devfreq_target(struct device *dev,
}
spin_unlock_irqrestore(hba->host->host_lock, irq_flags);

+ pm_runtime_get_noresume(hba->dev);
+ if (!pm_runtime_active(hba->dev)) {
+ pm_runtime_put_noidle(hba->dev);
+ ret = -EAGAIN;
+ goto out;
+ }
start = ktime_get();
ret = ufshcd_devfreq_scale(hba, scale_up);
+ pm_runtime_put(hba->dev);

trace_ufshcd_profile_clk_scaling(dev_name(hba->dev),
(scale_up ? "up" : "down"),
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
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