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[135/379,SRU,OEM-5.6] bus: mhi: core: Handle write lock properly in mhi_pm_m0_transition

Message ID 20201223085152.554896-136-vicamo.yang@canonical.com
State Accepted
Headers show
Series Support Qualcomm QCA6390 via ath11k driver | expand

Commit Message

You-Sheng Yang Dec. 23, 2020, 8:47 a.m. UTC 
From: Hemant Kumar <hemantk@codeaurora.org>

BugLink: https://bugs.launchpad.net/bugs/1879633

Take write lock only to protect db_mode member of mhi channel.
This allows rest of the mhi channels to just take read lock which
fine grains the locking. It prevents channel readers to starve if
they try to enter critical section after a writer.

Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20200521170249.21795-14-manivannan.sadhasivam@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 3bc1a5f431618a656bbf674a4627ef4da3a0d893)
Signed-off-by: You-Sheng Yang <vicamo.yang@canonical.com>
---
 drivers/bus/mhi/core/pm.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/drivers/bus/mhi/core/pm.c b/drivers/bus/mhi/core/pm.c
index 345f197130b8..de5abb26bcae 100644
--- a/drivers/bus/mhi/core/pm.c
+++ b/drivers/bus/mhi/core/pm.c
@@ -288,14 +288,18 @@  int mhi_pm_m0_transition(struct mhi_controller *mhi_cntrl)
 	for (i = 0; i < mhi_cntrl->max_chan; i++, mhi_chan++) {
 		struct mhi_ring *tre_ring = &mhi_chan->tre_ring;
 
-		write_lock_irq(&mhi_chan->lock);
-		if (mhi_chan->db_cfg.reset_req)
+		if (mhi_chan->db_cfg.reset_req) {
+			write_lock_irq(&mhi_chan->lock);
 			mhi_chan->db_cfg.db_mode = true;
+			write_unlock_irq(&mhi_chan->lock);
+		}
+
+		read_lock_irq(&mhi_chan->lock);
 
 		/* Only ring DB if ring is not empty */
 		if (tre_ring->base && tre_ring->wp  != tre_ring->rp)
 			mhi_ring_chan_db(mhi_cntrl, mhi_chan);
-		write_unlock_irq(&mhi_chan->lock);
+		read_unlock_irq(&mhi_chan->lock);
 	}
 
 	mhi_cntrl->wake_put(mhi_cntrl, false);