[PATCH v2] drm/bridge: ps8640: propagate AUX transfer register errors

[Pengpeng Hou]

ps8640_aux_transfer_msg() programs the AUX address registers, starts the
AUX transfer, waits for SWAUX_SEND to clear, and reads the AUX status
register. Several of those regmap operations have return values, but the
function only checks a stale ret after the status read.

Propagate failures from the address write, transfer start, completion
poll, and status read. This avoids returning a transfer length when the
bridge register transaction or AUX completion wait failed.

Fixes: 13afcdd7277e ("drm/bridge: parade-ps8640: Add support for AUX channel")
Signed-off-by: Pengpeng Hou <pengp...@iscas.ac.cn>
---
Changes since v1: 
https://lore.kernel.org/all/20260623060635.16064-1-pengp...@iscas.ac.cn/
- include the AUX address and length in the address-write diagnostic
- describe poll failures without assuming that every error is a timeout
- add the Fixes tag suggested by Doug
- rebase onto the current drm-misc-next tree

 drivers/gpu/drm/bridge/parade-ps8640.c | 27 +++++++++++++++++++++------
 1 file changed, 21 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c 
b/drivers/gpu/drm/bridge/parade-ps8640.c
index 96332721cb69..56b48f8feab6 100644
--- a/drivers/gpu/drm/bridge/parade-ps8640.c
+++ b/drivers/gpu/drm/bridge/parade-ps8640.c
@@ -257,8 +257,14 @@ static ssize_t ps8640_aux_transfer_msg(struct drm_dp_aux 
*aux,
        addr_len[PAGE0_SWAUX_LENGTH - base] = (len == 0) ? SWAUX_NO_PAYLOAD :
                                              ((len - 1) & SWAUX_LENGTH_MASK);
 
-       regmap_bulk_write(map, PAGE0_SWAUX_ADDR_7_0, addr_len,
-                         ARRAY_SIZE(addr_len));
+       ret = regmap_bulk_write(map, PAGE0_SWAUX_ADDR_7_0, addr_len,
+                               ARRAY_SIZE(addr_len));
+       if (ret) {
+               DRM_DEV_ERROR(dev,
+                             "failed to write AUX address %#x, len %zu: %d\n",
+                             msg->address, len, ret);
+               return ret;
+       }
 
        if (len && (request == DP_AUX_NATIVE_WRITE ||
                    request == DP_AUX_I2C_WRITE)) {
@@ -274,13 +280,22 @@ static ssize_t ps8640_aux_transfer_msg(struct drm_dp_aux 
*aux,
                }
        }
 
-       regmap_write(map, PAGE0_SWAUX_CTRL, SWAUX_SEND);
+       ret = regmap_write(map, PAGE0_SWAUX_CTRL, SWAUX_SEND);
+       if (ret) {
+               DRM_DEV_ERROR(dev, "failed to start AUX transfer: %d\n", ret);
+               return ret;
+       }
 
        /* Zero delay loop because i2c transactions are slow already */
-       regmap_read_poll_timeout(map, PAGE0_SWAUX_CTRL, data,
-                                !(data & SWAUX_SEND), 0, 50 * 1000);
+       ret = regmap_read_poll_timeout(map, PAGE0_SWAUX_CTRL, data,
+                                      !(data & SWAUX_SEND), 0, 50 * 1000);
+       if (ret) {
+               DRM_DEV_ERROR(dev, "failed to complete AUX transfer: %d\n",
+                             ret);
+               return ret;
+       }
 
-       regmap_read(map, PAGE0_SWAUX_STATUS, &data);
+       ret = regmap_read(map, PAGE0_SWAUX_STATUS, &data);
        if (ret) {
                DRM_DEV_ERROR(dev, "failed to read PAGE0_SWAUX_STATUS: %d\n",
                              ret);
-- 
2.50.1 (Apple Git-155)