[PATCH v2 1/2] ufs: core: Introduce ufshcd_mcq_poll_n_cqe_lock()

[Bart Van Assche <bvanassche@acm.org>]

Introduce a new function for processing completions that accepts an
upper limit for the number of completions to poll. Tell
ufshcd_mcq_poll_cqe_lock() to poll at most hwq->max_entries. This is
sufficient to poll all pending completions since there are never more
than hwq->max_entries - 1 completions on a completion queue. This patch
prepares for reducing the interrupt latency.

Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
 drivers/ufs/core/ufs-mcq.c | 14 +++++++++++---
 include/ufs/ufshcd.h       |  3 +++
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/ufs/core/ufs-mcq.c b/drivers/ufs/core/ufs-mcq.c
index 1b3062577945..e6081b97ed74 100644
--- a/drivers/ufs/core/ufs-mcq.c
+++ b/drivers/ufs/core/ufs-mcq.c
@@ -340,15 +340,16 @@ void ufshcd_mcq_compl_all_cqes_lock(struct ufs_hba *hba,
 	spin_unlock_irqrestore(&hwq->cq_lock, flags);
 }
 
-unsigned long ufshcd_mcq_poll_cqe_lock(struct ufs_hba *hba,
-				       struct ufs_hw_queue *hwq)
+unsigned long ufshcd_mcq_poll_n_cqe_lock(struct ufs_hba *hba,
+					 struct ufs_hw_queue *hwq,
+					 unsigned int max_compl)
 {
 	unsigned long completed_reqs = 0;
 	unsigned long flags;
 
 	spin_lock_irqsave(&hwq->cq_lock, flags);
 	ufshcd_mcq_update_cq_tail_slot(hwq);
-	while (!ufshcd_mcq_is_cq_empty(hwq)) {
+	while (!ufshcd_mcq_is_cq_empty(hwq) && completed_reqs < max_compl) {
 		ufshcd_mcq_process_cqe(hba, hwq);
 		ufshcd_mcq_inc_cq_head_slot(hwq);
 		completed_reqs++;
@@ -360,6 +361,13 @@ unsigned long ufshcd_mcq_poll_cqe_lock(struct ufs_hba *hba,
 
 	return completed_reqs;
 }
+EXPORT_SYMBOL_GPL(ufshcd_mcq_poll_n_cqe_lock);
+
+unsigned long ufshcd_mcq_poll_cqe_lock(struct ufs_hba *hba,
+				       struct ufs_hw_queue *hwq)
+{
+	return ufshcd_mcq_poll_n_cqe_lock(hba, hwq, hwq->max_entries);
+}
 EXPORT_SYMBOL_GPL(ufshcd_mcq_poll_cqe_lock);
 
 void ufshcd_mcq_make_queues_operational(struct ufs_hba *hba)
diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
index cfbc75d8df83..aa5f9b31ea86 100644
--- a/include/ufs/ufshcd.h
+++ b/include/ufs/ufshcd.h
@@ -1475,6 +1475,9 @@ void ufshcd_mcq_config_mac(struct ufs_hba *hba, u32 max_active_cmds);
 unsigned int ufshcd_mcq_queue_cfg_addr(struct ufs_hba *hba);
 u32 ufshcd_mcq_read_cqis(struct ufs_hba *hba, int i);
 void ufshcd_mcq_write_cqis(struct ufs_hba *hba, u32 val, int i);
+unsigned long ufshcd_mcq_poll_n_cqe_lock(struct ufs_hba *hba,
+					 struct ufs_hw_queue *hwq,
+					 unsigned int max_compl);
 unsigned long ufshcd_mcq_poll_cqe_lock(struct ufs_hba *hba,
 					 struct ufs_hw_queue *hwq);
 void ufshcd_mcq_make_queues_operational(struct ufs_hba *hba);