[PATCH AUTOSEL 5.15 49/50] soundwire: cadence: Remove wasted space in response_buf

Sasha Levin
2023-03-03T21:56:02Z

From: Richard Fitzgerald <rf@opensource.cirrus.com>

[ Upstream commit 827c32d0df4bbe0d1c47d79f6a5eabfe9ac75216 ]

The response_buf was declared much larger (128 entries) than the number
of responses that could ever be written into it. The Cadence IP is
configurable up to a maximum of 32 entries, and the datasheet says
that RX_FIFO_AVAIL can be 2 larger than this. So allow up to 34
responses.

Also add checking in cdns_read_response() to prevent overflowing
reponse_buf if RX_FIFO_AVAIL contains an unexpectedly large number.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20221202161812.4186897-3-rf@opensource.cirrus.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/soundwire/cadence_master.c | 7 +++++++
drivers/soundwire/cadence_master.h | 13 ++++++++++++-
2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index 18d2f9b3e2010..b229e1e0d7d97 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -769,8 +769,15 @@ static void cdns_read_response(struct sdw_cdns *cdns)
u32 num_resp, cmd_base;
int i;

+ /* RX_FIFO_AVAIL can be 2 entries more than the FIFO size */
+ BUILD_BUG_ON(ARRAY_SIZE(cdns->response_buf) < CDNS_MCP_CMD_LEN + 2);
+
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 = ARRAY_SIZE(cdns->response_buf);
+ }

cmd_base = CDNS_MCP_CMD_BASE;

diff --git a/drivers/soundwire/cadence_master.h b/drivers/soundwire/cadence_master.h
index e587aede63bf0..e437a604429fa 100644
--- a/drivers/soundwire/cadence_master.h
+++ b/drivers/soundwire/cadence_master.h
@@ -8,6 +8,12 @@
#define SDW_CADENCE_GSYNC_KHZ 4 /* 4 kHz */
#define SDW_CADENCE_GSYNC_HZ (SDW_CADENCE_GSYNC_KHZ * 1000)

+/*
+ * The Cadence IP supports up to 32 entries in the FIFO, though implementations
+ * can configure the IP to have a smaller FIFO.
+ */
+#define CDNS_MCP_IP_MAX_CMD_LEN 32
+
/**
* struct sdw_cdns_pdi: PDI (Physical Data Interface) instance
*
@@ -119,7 +125,12 @@ struct sdw_cdns {
struct sdw_bus bus;
unsigned int instance;

- u32 response_buf[0x80];
+ /*
+ * The datasheet says the RX FIFO AVAIL can be 2 entries more
+ * than the FIFO capacity, so allow for this.
+ */
+ u32 response_buf[CDNS_MCP_IP_MAX_CMD_LEN + 2];
+
struct completion tx_complete;
struct sdw_defer *defer;

--
2.39.2