linux-kernel - [PATCH 5.15 057/189] firmware: arm_scmi: Remove clear channel call on the TX channel

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Date:   Mon, 18 Apr 2022 14:11:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Cristian Marussi <cristian.marussi@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 057/189] firmware: arm_scmi: Remove clear channel call on the TX channel

From: Cristian Marussi <cristian.marussi@....com>

[ Upstream commit 98f0d68f94ea21541e0050cc64fa108ade779839 ]

On SCMI transports whose channels are based on a shared resource the TX
channel area has to be acquired by the agent before placing the desired
command into the channel and it will be then relinquished by the platform
once the related reply has been made available into the channel.
On an RX channel the logic is reversed with the platform acquiring the
channel area and the agent reliquishing it once done by calling the
scmi_clear_channel() helper.

As a consequence, even in case of error, the agent must never try to clear
a TX channel from its side: restrict the existing clear channel call on the
the reply path only to delayed responses since they are indeed coming from
the RX channel.

Link: https://lore.kernel.org/r/20220224152404.12877-1-cristian.marussi@arm.com
Fixes: e9b21c96181c ("firmware: arm_scmi: Make .clear_channel optional")
Signed-off-by: Cristian Marussi <cristian.marussi@....com>
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/firmware/arm_scmi/driver.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index d76bab3aaac4..e815b8f98739 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -652,7 +652,8 @@ static void scmi_handle_response(struct scmi_chan_info *cinfo,

 	xfer = scmi_xfer_command_acquire(cinfo, msg_hdr);
 	if (IS_ERR(xfer)) {
-		scmi_clear_channel(info, cinfo);
+		if (MSG_XTRACT_TYPE(msg_hdr) == MSG_TYPE_DELAYED_RESP)
+			scmi_clear_channel(info, cinfo);
 		return;
 	}

-- 
2.35.1