Re: [PATCH v5 2/6] drm: lcdif: Drop unnecessary NULL pointer check on lcdif->bridge

[Marek Vasut]

On 5/8/23 07:57, Liu Ying wrote:

Hi,

diff --git a/drivers/gpu/drm/mxsfb/lcdif_kms.c 
b/drivers/gpu/drm/mxsfb/lcdif_kms.c
index 262bc43b1079..e54200a9fcb9 100644
--- a/drivers/gpu/drm/mxsfb/lcdif_kms.c
+++ b/drivers/gpu/drm/mxsfb/lcdif_kms.c
@@ -394,7 +394,7 @@ static void lcdif_crtc_mode_set_nofb(struct 
lcdif_drm_private *lcdif,
        struct drm_display_mode *m = &lcdif->crtc.state->adjusted_mode;
        u32 bus_flags = 0;

- if (lcdif->bridge && lcdif->bridge->timings)

+       if (lcdif->bridge->timings)
                bus_flags = lcdif->bridge->timings->input_bus_flags;
        else if (bridge_state)
                bus_flags = bridge_state->input_bus_cfg.flags;
@@ -463,30 +463,21 @@ static void lcdif_crtc_atomic_enable(struct drm_crtc 
*crtc,
        struct drm_display_mode *m = &lcdif->crtc.state->adjusted_mode;
        struct drm_bridge_state *bridge_state = NULL;
        struct drm_device *drm = lcdif->drm;
-       u32 bus_format = 0;
+       u32 bus_format;
        dma_addr_t paddr;

- /* If there is a bridge attached to the LCDIF, use its bus format */

-       if (lcdif->bridge) {
-               bridge_state =
-                       drm_atomic_get_new_bridge_state(state,
-                                                       lcdif->bridge);
-               if (!bridge_state)
-                       bus_format = MEDIA_BUS_FMT_FIXED;
-               else
-                       bus_format = bridge_state->input_bus_cfg.format;
-
-               if (bus_format == MEDIA_BUS_FMT_FIXED) {
-                       dev_warn_once(drm->dev,
-                                     "Bridge does not provide bus format, assuming 
MEDIA_BUS_FMT_RGB888_1X24.\n"
-                                     "Please fix bridge driver by handling 
atomic_get_input_bus_fmts.\n");
-                       bus_format = MEDIA_BUS_FMT_RGB888_1X24;
-               }
-       }
+       bridge_state = drm_atomic_get_new_bridge_state(state, lcdif->bridge);
+       if (!bridge_state)
+               bus_format = MEDIA_BUS_FMT_FIXED;
+       else
+               bus_format = bridge_state->input_bus_cfg.format;

The code below seems to change the logic slightly.

Could it happen that:
- bridge_state is valid (i.e. non-NULL)
- bridge_state->input_bus_cfg.format is set to 0 (i.e. not set) ?
  (note that MEDIA_BUS_FMT_FIXED is defined as 0x0001)

-       /* If all else fails, default to RGB888_1X24 */
-       if (!bus_format)
+       if (bus_format == MEDIA_BUS_FMT_FIXED) {
+               dev_warn_once(drm->dev,
+                             "Bridge does not provide bus format, assuming 
MEDIA_BUS_FMT_RGB888_1X24.\n"
+                             "Please fix bridge driver by handling 
atomic_get_input_bus_fmts.\n");
                bus_format = MEDIA_BUS_FMT_RGB888_1X24;
+       }

clk_set_rate(lcdif->clk, m->crtc_clock * 1000);

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