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

[Boris Brezillon <boris.brezillon@collabora.com>]

On Mon, 16 Dec 2019 16:02:36 +0100
Marek Szyprowski <m.szyprowski@samsung.com> wrote:

> Hi Boris,
> 
> On 16.12.2019 15:55, Boris Brezillon wrote:
> > On Mon, 16 Dec 2019 14:54:25 +0100
> > Marek Szyprowski <m.szyprowski@samsung.com> wrote:  
> >> 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@collabora.com>
> >>> Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
> >>> Reviewed-by: Laurent Pinchart <laurent.pinchart@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?  
> 
> This patch doesn't change anything.

Okay. Can you do a list_for_each_entry() on both encoder->bridge_chain
and dsi->bridge_chain (dump bridge pointers in a pr_info()) before and
after the list_splice_init() call?

> 
> > --->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)
> >
> >  
> Best regards