FAILED: patch "[PATCH] bus: mhi: host: Add spinlock to protect WP access when" failed to apply to 5.10-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x b89b6a863dd53bc70d8e52d50f9cfaef8ef5e9c9
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2024012614-satiable-cheese-4655@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^..

Possible dependencies:

b89b6a863dd5 ("bus: mhi: host: Add spinlock to protect WP access when queueing TREs")
a0f5a630668c ("bus: mhi: Move host MHI code to "host" directory")
4547a749be99 ("bus: mhi: core: Fix MHI runtime_pm behavior")
68731852f6e5 ("bus: mhi: core: Return EAGAIN if MHI ring is full")
a8f75cb348fd ("mhi: core: Factorize mhi queuing")
855a70c12021 ("bus: mhi: Add MHI PCI support for WWAN modems")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From b89b6a863dd53bc70d8e52d50f9cfaef8ef5e9c9 Mon Sep 17 00:00:00 2001
From: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>
Date: Mon, 11 Dec 2023 14:42:51 +0800
Subject: [PATCH] bus: mhi: host: Add spinlock to protect WP access when
 queueing TREs

Protect WP accesses such that multiple threads queueing buffers for
incoming data do not race.

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

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 189ff97cca53 ("bus: mhi: core: Add support for data transfer")
Signed-off-by: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>
Signed-off-by: Qiang Yu <quic_qianyu@xxxxxxxxxxx>
Reviewed-by: Jeffrey Hugo <quic_jhugo@xxxxxxxxxxx>
Tested-by: Jeffrey Hugo <quic_jhugo@xxxxxxxxxxx>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
Link: https://lore.kernel.org/r/1702276972-41296-2-git-send-email-quic_qianyu@xxxxxxxxxxx
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>

diff --git a/drivers/bus/mhi/host/main.c b/drivers/bus/mhi/host/main.c
index d80975f4bba8..ad7807e4b523 100644
--- a/drivers/bus/mhi/host/main.c
+++ b/drivers/bus/mhi/host/main.c
@@ -1124,17 +1124,15 @@ 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
@@ -1154,7 +1152,6 @@ 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;
@@ -1206,6 +1203,9 @@ int mhi_gen_tre(struct mhi_controller *mhi_cntrl, struct mhi_chan *mhi_chan,
 	int eot, eob, chain, bei;
 	int ret;
 
+	/* Protect accesses for reading and incrementing WP */
+	write_lock_bh(&mhi_chan->lock);
+
 	buf_ring = &mhi_chan->buf_ring;
 	tre_ring = &mhi_chan->tre_ring;
 
@@ -1223,8 +1223,10 @@ int mhi_gen_tre(struct mhi_controller *mhi_cntrl, struct mhi_chan *mhi_chan,
 
 	if (!info->pre_mapped) {
 		ret = mhi_cntrl->map_single(mhi_cntrl, buf_info);
-		if (ret)
+		if (ret) {
+			write_unlock_bh(&mhi_chan->lock);
 			return ret;
+		}
 	}
 
 	eob = !!(flags & MHI_EOB);
@@ -1241,6 +1243,8 @@ int mhi_gen_tre(struct mhi_controller *mhi_cntrl, struct mhi_chan *mhi_chan,
 	mhi_add_ring_element(mhi_cntrl, tre_ring);
 	mhi_add_ring_element(mhi_cntrl, buf_ring);
 
+	write_unlock_bh(&mhi_chan->lock);
+
 	return 0;
 }