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

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>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Tested-by: Marijn Suijten <marijn.suijten@somainline.org>
Patchwork: https://patchwork.freedesktop.org/patch/480501/
Link: https://lore.kernel.org/r/20220401231104.967193-1-dmitry.baryshkov@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index a4a0572..c983698 100644 (file)
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -1440,10 +1440,10 @@ 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
@@ -1462,10 +1462,14 @@ 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;
@@ -2333,9 +2337,12 @@ 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;
                }
 
                /*