linux-kernel - [PATCH 3/3] soundwire: cadence: Drain the RX FIFO after an IO timeout

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20221201134845.4055907-4-rf@opensource.cirrus.com>
Date:   Thu, 1 Dec 2022 13:48:45 +0000
From:   Richard Fitzgerald <rf@...nsource.cirrus.com>
To:     <vkoul@...nel.org>, <pierre-louis.bossart@...ux.intel.com>
CC:     <yung-chuan.liao@...ux.intel.com>, <sanyog.r.kale@...el.com>,
        <alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>,
        <patches@...nsource.cirrus.com>,
        Richard Fitzgerald <rf@...nsource.cirrus.com>
Subject: [PATCH 3/3] soundwire: cadence: Drain the RX FIFO after an IO timeout

If wait_for_completion_timeout() times-out in _cdns_xfer_msg() it
is possible that something could have been written to the RX FIFO.
In this case, we should drain the RX FIFO so that anything in it
doesn't carry over and mess up the next transfer.

Obviously, if we got to this state something went wrong, and we
don't really know the state of everything. The cleanup in this
situation cannot be bullet-proof but we should attempt to avoid
breaking future transaction, if only to reduce the amount of
error noise when debugging the failure from a kernel log.

Note that this patch only implements the draining for blocking
(non-deferred) transfers. The deferred API doesn't have any proper
handling of error conditions and would need some re-design before
implementing cleanup. That is a task for a separate patch...

Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
---
 drivers/soundwire/cadence_master.c | 48 ++++++++++++++++--------------
 1 file changed, 26 insertions(+), 22 deletions(-)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index 95c84d9f0775..6bffecf3d61a 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -555,6 +555,28 @@ cdns_fill_msg_resp(struct sdw_cdns *cdns,
 	return SDW_CMD_OK;
 }
 
+static void cdns_read_response(struct sdw_cdns *cdns)
+{
+	u32 num_resp, cmd_base;
+	int i;
+
+	BUILD_BUG_ON(ARRAY_SIZE(cdns->response_buf) < CDNS_MCP_CMD_LEN);
+
+	num_resp = cdns_readl(cdns, CDNS_MCP_FIFOSTAT);
+	num_resp &= CDNS_MCP_RX_FIFO_AVAIL;
+	if (num_resp > ARRAY_SIZE(cdns->response_buf)) {
+		dev_warn(cdns->dev, "RX AVAIL %d too long\n", num_resp);
+		num_resp = CDNS_MCP_CMD_LEN;
+	}
+
+	cmd_base = CDNS_MCP_CMD_BASE;
+
+	for (i = 0; i < num_resp; i++) {
+		cdns->response_buf[i] = cdns_readl(cdns, cmd_base);
+		cmd_base += CDNS_MCP_CMD_WORD_LEN;
+	}
+}
+
 static enum sdw_command_response
 _cdns_xfer_msg(struct sdw_cdns *cdns, struct sdw_msg *msg, int cmd,
 	       int offset, int count, bool defer)
@@ -596,6 +618,10 @@ _cdns_xfer_msg(struct sdw_cdns *cdns, struct sdw_msg *msg, int cmd,
 		dev_err(cdns->dev, "IO transfer timed out, cmd %d device %d addr %x len %d\n",
 			cmd, msg->dev_num, msg->addr, msg->len);
 		msg->len = 0;
+
+		/* Drain anything in the RX_FIFO */
+		cdns_read_response(cdns);
+
 		return SDW_CMD_TIMEOUT;
 	}
 
@@ -769,28 +795,6 @@ EXPORT_SYMBOL(cdns_read_ping_status);
  * IRQ handling
  */
 
-static void cdns_read_response(struct sdw_cdns *cdns)
-{
-	u32 num_resp, cmd_base;
-	int i;
-
-	BUILD_BUG_ON(ARRAY_SIZE(cdns->response_buf) < CDNS_MCP_CMD_LEN);
-
-	num_resp = cdns_readl(cdns, CDNS_MCP_FIFOSTAT);
-	num_resp &= CDNS_MCP_RX_FIFO_AVAIL;
-	if (num_resp > ARRAY_SIZE(cdns->response_buf)) {
-		dev_warn(cdns->dev, "RX AVAIL %d too long\n", num_resp);
-		num_resp = CDNS_MCP_CMD_LEN;
-	}
-
-	cmd_base = CDNS_MCP_CMD_BASE;
-
-	for (i = 0; i < num_resp; i++) {
-		cdns->response_buf[i] = cdns_readl(cdns, cmd_base);
-		cmd_base += CDNS_MCP_CMD_WORD_LEN;
-	}
-}
-
 static int cdns_update_slave_status(struct sdw_cdns *cdns,
 				    u64 slave_intstat)
 {
-- 
2.30.2