Patch "firmware: arm_scmi: Reset Rx buffer to max size during async commands" has been added to the 5.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    firmware: arm_scmi: Reset Rx buffer to max size during async commands

to the 5.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     firmware-arm_scmi-reset-rx-buffer-to-max-size-during.patch
and it can be found in the queue-5.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 2d3dea42bbbb0bb8599c77c4b70532b80b2a60c3
Author: Cristian Marussi <cristian.marussi@xxxxxxx>
Date:   Tue Jun 1 11:24:17 2021 +0100

    firmware: arm_scmi: Reset Rx buffer to max size during async commands
    
    [ Upstream commit 0cb7af474e0dbb2f500c67aa62b6db9fafa74de2 ]
    
    During an async commands execution the Rx buffer length is at first set
    to max_msg_sz when the synchronous part of the command is first sent.
    However once the synchronous part completes the transport layer waits
    for the delayed response which will be processed using the same xfer
    descriptor initially allocated. Since synchronous response received at
    the end of the xfer will shrink the Rx buffer length to the effective
    payload response length, it needs to be reset again.
    
    Raise the Rx buffer length again to max_msg_sz before fetching the
    delayed response to ensure full response is read correctly from the
    shared memory.
    
    Link: https://lore.kernel.org/r/20210601102421.26581-2-cristian.marussi@xxxxxxx
    Fixes: 58ecdf03dbb9 ("firmware: arm_scmi: Add support for asynchronous commands and delayed response")
    Signed-off-by: Cristian Marussi <cristian.marussi@xxxxxxx>
    [sudeep.holla: moved reset to scmi_handle_response as it could race with
                   do_xfer_with_response]
    Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 11078199abed..7b6903bad408 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -370,6 +370,10 @@ static void scmi_rx_callback(struct mbox_client *cl, void *m)
 
 	xfer = &minfo->xfer_block[xfer_id];
 
+	/* rx.len could be shrunk in the sync do_xfer, so reset to maxsz */
+	if (msg_type == MSG_TYPE_DELAYED_RESP)
+		xfer->rx.len = info->desc->max_msg_size;
+
 	scmi_dump_header_dbg(dev, &xfer->hdr);
 
 	scmi_fetch_response(xfer, mem);