[PATCH] drm/msm/dsi: fix error checks and return values for DSI xmit functions

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

As noticed by Dan ([1] an the followup thread) there are multiple issues
with the return values for MSM DSI command transmission callback. In
the error case it can easily return a positive value when it should
have returned a proper error code.

This commits attempts to fix these issues both in TX and in RX paths.

[1]: https://lore.kernel.org/linux-arm-msm/20211001123617.GH2283@kili/

Fixes: a689554ba6ed ("drm/msm: Initial add DSI connector support")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index d51e70fab93d..8925f60fd9ec 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -1341,10 +1341,10 @@ static int dsi_cmds2buf_tx(struct msm_dsi_host *msm_host,
 			dsi_get_bpp(msm_host->format) / 8;
 
 	len = dsi_cmd_dma_add(msm_host, msg);
-	if (!len) {
+	if (len < 0) {
 		pr_err("%s: failed to add cmd type = 0x%x\n",
 			__func__,  msg->type);
-		return -EINVAL;
+		return len;
 	}
 
 	/* for video mode, do not send cmds more than
@@ -1363,10 +1363,14 @@ static int dsi_cmds2buf_tx(struct msm_dsi_host *msm_host,
 	}
 
 	ret = dsi_cmd_dma_tx(msm_host, len);
-	if (ret < len) {
-		pr_err("%s: cmd dma tx failed, type=0x%x, data0=0x%x, len=%d\n",
-			__func__, msg->type, (*(u8 *)(msg->tx_buf)), len);
-		return -ECOMM;
+	if (ret < 0) {
+		pr_err("%s: cmd dma tx failed, type=0x%x, data0=0x%x, len=%d, ret=%d\n",
+			__func__, msg->type, (*(u8 *)(msg->tx_buf)), len, ret);
+		return ret;
+	} else if (ret < len) {
+		pr_err("%s: cmd dma tx failed, type=0x%x, data0=0x%x, ret=%d len=%d\n",
+			__func__, msg->type, (*(u8 *)(msg->tx_buf)), ret, len);
+		return -EIO;
 	}
 
 	return len;
@@ -2092,9 +2096,12 @@ int msm_dsi_host_cmd_rx(struct mipi_dsi_host *host,
 		}
 
 		ret = dsi_cmds2buf_tx(msm_host, msg);
-		if (ret < msg->tx_len) {
+		if (ret < 0) {
 			pr_err("%s: Read cmd Tx failed, %d\n", __func__, ret);
 			return ret;
+		} else if (ret < msg->tx_len) {
+			pr_err("%s: Read cmd Tx failed, too short: %d\n", __func__, ret);
+			return -ECOMM;
 		}
 
 		/*
-- 
2.35.1