[PATCH v4 04/11] drm/bridge: Make the bridge chain a double-linked list

[Boris Brezillon]

Hello Marek,

On Mon, 16 Dec 2019 14:54:25 +0100
Marek Szyprowski <m.szyprowski at samsung.com> wrote:

> Hi All,
> 
> On 03.12.2019 15:15, Boris Brezillon wrote:
> > So that each element in the chain can easily access its predecessor.
> > This will be needed to support bus format negotiation between elements
> > of the bridge chain.
> >
> > Signed-off-by: Boris Brezillon <boris.brezillon at collabora.com>
> > Reviewed-by: Neil Armstrong <narmstrong at baylibre.com>
> > Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>  
> 
> I've noticed that this patch got merged to linux-next as commit 
> 05193dc38197021894b17239fafbd2eb1afe5a45. Sadly it breaks booting of 
> Samsung Exynos5250-based Arndale board. Booting stops after following 
> messages:
> 
> [drm] Exynos DRM: using 14400000.fimd device for DMA mapping operations
> exynos-drm exynos-drm: bound 14400000.fimd (ops fimd_component_ops)
> exynos-drm exynos-drm: bound 14450000.mixer (ops mixer_component_ops)
> exynos-drm exynos-drm: bound 14500000.dsi (ops exynos_dsi_component_ops)
> exynos-drm exynos-drm: bound 14530000.hdmi (ops hdmi_component_ops)
> [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
> [drm] No driver support for vblank timestamp query.
> [drm] Cannot find any crtc or sizes
> [drm] Cannot find any crtc or sizes
> [drm] Initialized exynos 1.1.0 20180330 for exynos-drm on minor 0
> 
> I will try to debug this and provide more information soon.
> 

Can you try with this diff applied?

--->8---
diff --git a/drivers/gpu/drm/exynos/exynos_drm_dsi.c b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
index 3955f84dc893..118ecedc7621 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_dsi.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
@@ -1523,7 +1523,7 @@ static int exynos_dsi_host_attach(struct mipi_dsi_host *host,
        if (out_bridge) {
                drm_bridge_attach(encoder, out_bridge, NULL);
                dsi->out_bridge = out_bridge;
-               list_splice(&encoder->bridge_chain, &dsi->bridge_chain);
+               list_splice_init(&encoder->bridge_chain, &dsi->bridge_chain);
        } else {
                int ret = exynos_dsi_create_connector(encoder);
 
diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
index 6c5b80ad6154..e1378d48210f 100644
--- a/drivers/gpu/drm/vc4/vc4_dsi.c
+++ b/drivers/gpu/drm/vc4/vc4_dsi.c
@@ -1613,7 +1613,7 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
         * from our driver, since we need to sequence them within the
         * encoder's enable/disable paths.
         */
-       list_splice(&dsi->encoder->bridge_chain, &dsi->bridge_chain);
+       list_splice_init(&dsi->encoder->bridge_chain, &dsi->bridge_chain);
 
        if (dsi->port == 0)
                vc4_debugfs_add_regset32(drm, "dsi0_regs", &dsi->regset);
@@ -1639,7 +1639,7 @@ static void vc4_dsi_unbind(struct device *dev, struct device *master,
         * Restore the bridge_chain so the bridge detach procedure can happen
         * normally.
         */
-       list_splice(&dsi->bridge_chain, &dsi->encoder->bridge_chain);
+       list_splice_init(&dsi->bridge_chain, &dsi->encoder->bridge_chain);
        vc4_dsi_encoder_destroy(dsi->encoder);
 
        if (dsi->port == 1)