Re: [PATCH v4 4/4] bus: mhi: host: Take irqsave lock after TRE is generated

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On 11/24/2023 6:09 PM, Manivannan Sadhasivam wrote:
On Tue, Nov 14, 2023 at 01:27:41PM +0800, Qiang Yu wrote:
From: Hemant Kumar <quic_hemantk@xxxxxxxxxxx>

If CONFIG_TRACE_IRQFLAGS is enabled, irq will be enabled once __local_bh_
enable_ip is called as part of write_unlock_bh. Hence, let's take irqsave
"__local_bh_enable_ip" is a function name, so you should not break it.
Thanks for let me know, will note this in following patch.

lock after TRE is generated to avoid running write_unlock_bh when irqsave
lock is held.

I still don't understand this commit message. Where is the write_unlock_bh()
being called?

- Mani
Write_unlock_bh() is invoked in mhi_gen_te()
The calling flow is like
mhi_queue
    read_lock_irqsave(&mhi_cntrl->pm_lock, flags)
    mhi_gen_tre
        write_lock_bh(&mhi_chan->lock)
        write_unlock_bh(&mhi_chan->lock)   // Will enable irq if CONFIG_TRACE_IRQFLAGS is enabled
    read_lock_irqsave(&mhi_cntrl->pm_lock, flags)

after adding this patch, the calling flow becomes

mhi_queue
    mhi_gen_tre
        write_lock_bh(&mhi_chan->lock)
        write_unlock_bh(&mhi_chan->lock)
    read_lock_irqsave(&mhi_cntrl->pm_lock, flags)
    read_lock_irqsave(&mhi_cntrl->pm_lock, flags)

Signed-off-by: Hemant Kumar <quic_hemantk@xxxxxxxxxxx>
Signed-off-by: Lazarus Motha <quic_lmotha@xxxxxxxxxxx>
Signed-off-by: Qiang Yu <quic_qianyu@xxxxxxxxxxx>
---
  drivers/bus/mhi/host/main.c | 13 +++++--------
  1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
index 33f27e2..d7abd0b 100644
--- a/drivers/bus/mhi/host/main.c
+++ b/drivers/bus/mhi/host/main.c
@@ -1128,17 +1128,15 @@ static int mhi_queue(struct mhi_device *mhi_dev, struct mhi_buf_info *buf_info,
  	if (unlikely(MHI_PM_IN_ERROR_STATE(mhi_cntrl->pm_state)))
  		return -EIO;
- read_lock_irqsave(&mhi_cntrl->pm_lock, flags);
-
  	ret = mhi_is_ring_full(mhi_cntrl, tre_ring);
-	if (unlikely(ret)) {
-		ret = -EAGAIN;
-		goto exit_unlock;
-	}
+	if (unlikely(ret))
+		return -EAGAIN;
ret = mhi_gen_tre(mhi_cntrl, mhi_chan, buf_info, mflags);
  	if (unlikely(ret))
-		goto exit_unlock;
+		return ret;
+
+	read_lock_irqsave(&mhi_cntrl->pm_lock, flags);
/* Packet is queued, take a usage ref to exit M3 if necessary
  	 * for host->device buffer, balanced put is done on buffer completion
@@ -1158,7 +1156,6 @@ static int mhi_queue(struct mhi_device *mhi_dev, struct mhi_buf_info *buf_info,
  	if (dir == DMA_FROM_DEVICE)
  		mhi_cntrl->runtime_put(mhi_cntrl);
-exit_unlock:
  	read_unlock_irqrestore(&mhi_cntrl->pm_lock, flags);
return ret;
--
2.7.4






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