scsi: ufs: Make ufshcd_wait_for_register() sleep instead of busy-waiting

The ufshcd_wait_for_register() function either sleeps or spins until the
specified register has reached the desired value. Busy-waiting is not only
considered a bad practice but also has a bad impact on energy
consumption. Always sleep instead of spinning by making sure that all
ufshcd_wait_for_register() calls happen from a context where it is allowed
to sleep. The only function call that has to be moved is the
ufshcd_hba_stop() call in ufshcd_host_reset_and_restore().

Link: https://lore.kernel.org/r/20200507222750.19113-1-bvanassche@acm.org
Cc: Can Guo <cang@codeaurora.org>
Cc: Avri Altman <avri.altman@wdc.com>
Cc: Bean Huo <beanhuo@micron.com>
Cc: Alim Akhtar <alim.akhtar@samsung.com>
Cc: Asutosh Das <asutoshd@codeaurora.org>
Tested-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: Bart Van Assche <bvanassche@acm.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 aca50ed..c3389c9 100644 (file)
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -562,21 +562,21 @@ void ufshcd_delay_us(unsigned long us, unsigned long tolerance)
 }
 EXPORT_SYMBOL_GPL(ufshcd_delay_us);
 
-/*
+/**
  * ufshcd_wait_for_register - wait for register value to change
- * @hba - per-adapter interface
- * @reg - mmio register offset
- * @mask - mask to apply to read register value
- * @val - wait condition
- * @interval_us - polling interval in microsecs
- * @timeout_ms - timeout in millisecs
- * @can_sleep - perform sleep or just spin
+ * @hba: per-adapter interface
+ * @reg: mmio register offset
+ * @mask: mask to apply to the read register value
+ * @val: value to wait for
+ * @interval_us: polling interval in microseconds
+ * @timeout_ms: timeout in milliseconds
  *
- * Returns -ETIMEDOUT on error, zero on success
+ * Return:
+ * -ETIMEDOUT on error, zero on success.
  */
 int ufshcd_wait_for_register(struct ufs_hba *hba, u32 reg, u32 mask,
                                u32 val, unsigned long interval_us,
-                               unsigned long timeout_ms, bool can_sleep)
+                               unsigned long timeout_ms)
 {
        int err = 0;
        unsigned long timeout = jiffies + msecs_to_jiffies(timeout_ms);
@@ -585,10 +585,7 @@ int ufshcd_wait_for_register(struct ufs_hba *hba, u32 reg, u32 mask,
        val = val & mask;
 
        while ((ufshcd_readl(hba, reg) & mask) != val) {
-               if (can_sleep)
-                       usleep_range(interval_us, interval_us + 50);
-               else
-                       udelay(interval_us);
+               usleep_range(interval_us, interval_us + 50);
                if (time_after(jiffies, timeout)) {
                        if ((ufshcd_readl(hba, reg) & mask) != val)
                                err = -ETIMEDOUT;
@@ -2577,7 +2574,7 @@ ufshcd_clear_cmd(struct ufs_hba *hba, int tag)
         */
        err = ufshcd_wait_for_register(hba,
                        REG_UTP_TRANSFER_REQ_DOOR_BELL,
-                       mask, ~mask, 1000, 1000, true);
+                       mask, ~mask, 1000, 1000);
 
        return err;
 }
@@ -4247,16 +4244,23 @@ EXPORT_SYMBOL_GPL(ufshcd_make_hba_operational);
 /**
  * ufshcd_hba_stop - Send controller to reset state
  * @hba: per adapter instance
- * @can_sleep: perform sleep or just spin
  */
-static inline void ufshcd_hba_stop(struct ufs_hba *hba, bool can_sleep)
+static inline void ufshcd_hba_stop(struct ufs_hba *hba)
 {
+       unsigned long flags;
        int err;
 
+       /*
+        * Obtain the host lock to prevent that the controller is disabled
+        * while the UFS interrupt handler is active on another CPU.
+        */
+       spin_lock_irqsave(hba->host->host_lock, flags);
        ufshcd_writel(hba, CONTROLLER_DISABLE,  REG_CONTROLLER_ENABLE);
+       spin_unlock_irqrestore(hba->host->host_lock, flags);
+
        err = ufshcd_wait_for_register(hba, REG_CONTROLLER_ENABLE,
                                        CONTROLLER_ENABLE, CONTROLLER_DISABLE,
-                                       10, 1, can_sleep);
+                                       10, 1);
        if (err)
                dev_err(hba->dev, "%s: Controller disable failed\n", __func__);
 }
@@ -4277,7 +4281,7 @@ int ufshcd_hba_enable(struct ufs_hba *hba)
 
        if (!ufshcd_is_hba_active(hba))
                /* change controller state to "reset state" */
-               ufshcd_hba_stop(hba, true);
+               ufshcd_hba_stop(hba);
 
        /* UniPro link is disabled at this point */
        ufshcd_set_link_off(hba);
@@ -5906,7 +5910,7 @@ static int ufshcd_clear_tm_cmd(struct ufs_hba *hba, int tag)
        /* poll for max. 1 sec to clear door bell register by h/w */
        err = ufshcd_wait_for_register(hba,
                        REG_UTP_TASK_REQ_DOOR_BELL,
-                       mask, 0, 1000, 1000, true);
+                       mask, 0, 1000, 1000);
 out:
        return err;
 }
@@ -6482,8 +6486,9 @@ static int ufshcd_host_reset_and_restore(struct ufs_hba *hba)
         * Stop the host controller and complete the requests
         * cleared by h/w
         */
+       ufshcd_hba_stop(hba);
+
        spin_lock_irqsave(hba->host->host_lock, flags);
-       ufshcd_hba_stop(hba, false);
        hba->silence_err_logs = true;
        ufshcd_complete_requests(hba);
        hba->silence_err_logs = false;
@@ -8049,7 +8054,7 @@ static int ufshcd_link_state_transition(struct ufs_hba *hba,
                 * Change controller state to "reset state" which
                 * should also put the link in off/reset state
                 */
-               ufshcd_hba_stop(hba, true);
+               ufshcd_hba_stop(hba);
                /*
                 * TODO: Check if we need any delay to make sure that
                 * controller is reset
@@ -8608,7 +8613,7 @@ void ufshcd_remove(struct ufs_hba *hba)
        scsi_remove_host(hba->host);
        /* disable interrupts */
        ufshcd_disable_intr(hba, hba->intr_mask);
-       ufshcd_hba_stop(hba, true);
+       ufshcd_hba_stop(hba);
 
        ufshcd_exit_clk_scaling(hba);
        ufshcd_exit_clk_gating(hba);

diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index e3dfb48..88d4202 100644 (file)
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -831,7 +831,7 @@ int ufshcd_uic_hibern8_exit(struct ufs_hba *hba);
 void ufshcd_delay_us(unsigned long us, unsigned long tolerance);
 int ufshcd_wait_for_register(struct ufs_hba *hba, u32 reg, u32 mask,
                                u32 val, unsigned long interval_us,
-                               unsigned long timeout_ms, bool can_sleep);
+                               unsigned long timeout_ms);
 void ufshcd_parse_dev_ref_clk_freq(struct ufs_hba *hba, struct clk *refclk);
 void ufshcd_update_reg_hist(struct ufs_err_reg_hist *reg_hist,
                            u32 reg);