[PATCH 2/4] ufs: Simplify the clock scaling mechanism implementation

Bart Van Assche
2019-10-31T22:55:39Z

Scaling the clock is only safe while no commands are in progress. Use
blk_mq_{un,}freeze_queue() to block submission of new commands and to
wait for ongoing commands to complete.

Cc: Yaniv Gardi <ygardi@codeaurora.org>
Cc: Subhash Jadavani <subhashj@codeaurora.org>
Cc: Stanley Chu <stanley.chu@mediatek.com>
Cc: Avri Altman <avri.altman@wdc.com>
Cc: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
drivers/scsi/ufs/ufshcd.c | 131 ++++++++++++--------------------------
drivers/scsi/ufs/ufshcd.h | 3 -
2 files changed, 40 insertions(+), 94 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index da9677fb2d5d..b7e27d86a0ec 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -292,14 +292,46 @@ static inline void ufshcd_disable_irq(struct ufs_hba *hba)

static void ufshcd_scsi_unblock_requests(struct ufs_hba *hba)
{
- if (atomic_dec_and_test(&hba->scsi_block_reqs_cnt))
- scsi_unblock_requests(hba->host);
+ struct scsi_device *sdev;
+
+ blk_mq_unfreeze_queue(hba->tag_alloc_queue);
+ shost_for_each_device(sdev, hba->host)
+ blk_mq_unfreeze_queue(sdev->request_queue);
}

-static void ufshcd_scsi_block_requests(struct ufs_hba *hba)
+static int ufshcd_scsi_block_requests(struct ufs_hba *hba,
+ unsigned long timeout)
{
- if (atomic_inc_return(&hba->scsi_block_reqs_cnt) == 1)
- scsi_block_requests(hba->host);
+ struct scsi_device *sdev;
+ unsigned long deadline = jiffies + timeout;
+ bool success = true;
+
+ if (timeout == ULONG_MAX) {
+ shost_for_each_device(sdev, hba->host)
+ blk_mq_freeze_queue(sdev->request_queue);
+ blk_mq_freeze_queue(hba->tag_alloc_queue);
+ return 0;
+ }
+
+ shost_for_each_device(sdev, hba->host)
+ blk_freeze_queue_start(sdev->request_queue);
+ blk_freeze_queue_start(hba->tag_alloc_queue);
+ if (blk_mq_freeze_queue_wait_timeout(hba->tag_alloc_queue,
+ max_t(long, 0, deadline - jiffies)) <= 0)
+ goto err;
+ shost_for_each_device(sdev, hba->host) {
+ if (blk_mq_freeze_queue_wait_timeout(sdev->request_queue,
+ max_t(long, 0, deadline - jiffies)) <= 0) {
+ success = false;
+ break;
+ }
+ }
+ if (!success) {
+err:
+ ufshcd_scsi_unblock_requests(hba);
+ return -ETIMEDOUT;
+ }
+ return 0;
}

static void ufshcd_add_cmd_upiu_trace(struct ufs_hba *hba, unsigned int tag,
@@ -1005,65 +1037,6 @@ static bool ufshcd_is_devfreq_scaling_required(struct ufs_hba *hba,
return false;
}

-static int ufshcd_wait_for_doorbell_clr(struct ufs_hba *hba,
- u64 wait_timeout_us)
-{
- unsigned long flags;
- int ret = 0;
- u32 tm_doorbell;
- u32 tr_doorbell;
- bool timeout = false, do_last_check = false;
- ktime_t start;
-
- ufshcd_hold(hba, false);
- spin_lock_irqsave(hba->host->host_lock, flags);
- /*
- * Wait for all the outstanding tasks/transfer requests.
- * Verify by checking the doorbell registers are clear.
- */
- start = ktime_get();
- do {
- if (hba->ufshcd_state != UFSHCD_STATE_OPERATIONAL) {
- ret = -EBUSY;
- goto out;
- }
-
- tm_doorbell = ufshcd_readl(hba, REG_UTP_TASK_REQ_DOOR_BELL);
- tr_doorbell = ufshcd_readl(hba, REG_UTP_TRANSFER_REQ_DOOR_BELL);
- if (!tm_doorbell && !tr_doorbell) {
- timeout = false;
- break;
- } else if (do_last_check) {
- break;
- }
-
- spin_unlock_irqrestore(hba->host->host_lock, flags);
- schedule();
- if (ktime_to_us(ktime_sub(ktime_get(), start)) >
- wait_timeout_us) {
- timeout = true;
- /*
- * We might have scheduled out for long time so make
- * sure to check if doorbells are cleared by this time
- * or not.
- */
- do_last_check = true;
- }
- spin_lock_irqsave(hba->host->host_lock, flags);
- } while (tm_doorbell || tr_doorbell);
-
- if (timeout) {
- dev_err(hba->dev,
- "%s: timedout waiting for doorbell to clear (tm=0x%x, tr=0x%x)\n",
- __func__, tm_doorbell, tr_doorbell);
- ret = -EBUSY;
- }
-out:
- spin_unlock_irqrestore(hba->host->host_lock, flags);
- ufshcd_release(hba);
- return ret;
-}
-
/**
* ufshcd_scale_gear - scale up/down UFS gear
* @hba: per adapter instance
@@ -1113,26 +1086,15 @@ static int ufshcd_scale_gear(struct ufs_hba *hba, bool scale_up)

static int ufshcd_clock_scaling_prepare(struct ufs_hba *hba)
{
- #define DOORBELL_CLR_TOUT_US (1000 * 1000) /* 1 sec */
- int ret = 0;
/*
* make sure that there are no outstanding requests when
* clock scaling is in progress
*/
- ufshcd_scsi_block_requests(hba);
- down_write(&hba->clk_scaling_lock);
- if (ufshcd_wait_for_doorbell_clr(hba, DOORBELL_CLR_TOUT_US)) {
- ret = -EBUSY;
- up_write(&hba->clk_scaling_lock);
- ufshcd_scsi_unblock_requests(hba);
- }
-
- return ret;
+ return ufshcd_scsi_block_requests(hba, HZ);
}

static void ufshcd_clock_scaling_unprepare(struct ufs_hba *hba)
{
- up_write(&hba->clk_scaling_lock);
ufshcd_scsi_unblock_requests(hba);
}

@@ -1562,7 +1524,7 @@ int ufshcd_hold(struct ufs_hba *hba, bool async)
*/
/* fallthrough */
case CLKS_OFF:
- ufshcd_scsi_block_requests(hba);
+ ufshcd_scsi_block_requests(hba, ULONG_MAX);
hba->clk_gating.state = REQ_CLKS_ON;
trace_ufshcd_clk_gating(dev_name(hba->dev),
hba->clk_gating.state);
@@ -2428,9 +2390,6 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
BUG();
}

- if (!down_read_trylock(&hba->clk_scaling_lock))
- return SCSI_MLQUEUE_HOST_BUSY;
-
spin_lock_irqsave(hba->host->host_lock, flags);
switch (hba->ufshcd_state) {
case UFSHCD_STATE_OPERATIONAL:
@@ -2495,7 +2454,6 @@ static int ufshcd_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *cmd)
out_unlock:
spin_unlock_irqrestore(hba->host->host_lock, flags);
out:
- up_read(&hba->clk_scaling_lock);
return err;
}

@@ -2649,8 +2607,6 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,
struct completion wait;
unsigned long flags;

- down_read(&hba->clk_scaling_lock);
-
/*
* Get free slot, sleep if slots are unavailable.
* Even though we use wait_event() which sleeps indefinitely,
@@ -2684,7 +2640,6 @@ static int ufshcd_exec_dev_cmd(struct ufs_hba *hba,

out_put_tag:
blk_put_request(req);
- up_read(&hba->clk_scaling_lock);
return err;
}

@@ -5483,7 +5438,7 @@ static void ufshcd_check_errors(struct ufs_hba *hba)
/* handle fatal errors only when link is functional */
if (hba->ufshcd_state == UFSHCD_STATE_OPERATIONAL) {
/* block commands from scsi mid-layer */
- ufshcd_scsi_block_requests(hba);
+ ufshcd_scsi_block_requests(hba, ULONG_MAX);

hba->ufshcd_state = UFSHCD_STATE_EH_SCHEDULED;

@@ -5760,8 +5715,6 @@ static int ufshcd_issue_devman_upiu_cmd(struct ufs_hba *hba,
unsigned long flags;
u32 upiu_flags;

- down_read(&hba->clk_scaling_lock);
-
req = blk_get_request(q, REQ_OP_DRV_IN, 0);
if (IS_ERR(req))
return PTR_ERR(req);
@@ -5840,7 +5793,6 @@ static int ufshcd_issue_devman_upiu_cmd(struct ufs_hba *hba,
}

blk_put_request(req);
- up_read(&hba->clk_scaling_lock);
return err;
}

@@ -8320,8 +8272,6 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)
/* Initialize mutex for device management commands */
mutex_init(&hba->dev_cmd.lock);

- init_rwsem(&hba->clk_scaling_lock);
-
ufshcd_init_clk_gating(hba);

ufshcd_init_clk_scaling(hba);
@@ -8387,7 +8337,6 @@ int ufshcd_init(struct ufs_hba *hba, void __iomem *mmio_base, unsigned int irq)

/* Hold auto suspend until async scan completes */
pm_runtime_get_sync(dev);
- atomic_set(&hba->scsi_block_reqs_cnt, 0);
/*
* We are assuming that device wasn't put in sleep/power-down
* state exclusively during the boot stage before kernel.
diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
index 8fa33fb71237..fd88a9de3519 100644
--- a/drivers/scsi/ufs/ufshcd.h
+++ b/drivers/scsi/ufs/ufshcd.h
@@ -522,7 +522,6 @@ struct ufs_stats {
* @urgent_bkops_lvl: keeps track of urgent bkops level for device
* @is_urgent_bkops_lvl_checked: keeps track if the urgent bkops level for
* device is known or not.
- * @scsi_block_reqs_cnt: reference counting for scsi block requests
*/
struct ufs_hba {
void __iomem *mmio_base;
@@ -728,9 +727,7 @@ struct ufs_hba {
enum bkops_status urgent_bkops_lvl;
bool is_urgent_bkops_lvl_checked;

- struct rw_semaphore clk_scaling_lock;
struct ufs_desc_size desc_size;
- atomic_t scsi_block_reqs_cnt;

struct device bsg_dev;
struct request_queue *bsg_queue;
--
2.24.0.rc0.303.g954a862665-goog