scsi: ufs: Make sure clk scaling happens only when HBA is runtime ACTIVE

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.
This can lead to unexpected error. We cannot just protect it by calling
pm_runtime_get_sync() because that may cause a race condition since HBA
runtime suspend ops need to suspend clk scaling. To fix this call
pm_runtime_get_noresume() and check HBA's runtime status. 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

Link: https://lore.kernel.org/r/1600758548-28576-1-git-send-email-cang@codeaurora.org
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 180e64d..20b16de 100644 (file)
--- 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"),