linux-kernel - Re: [PATCH v3 01/12] drm/bridge: Fix the stop condition of drm_bridge_chain_pre

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Date:   Thu, 15 Apr 2021 04:56:50 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Doug Anderson <dianders@...omium.org>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Sam Ravnborg <sam@...nborg.org>,
        Linus W <linus.walleij@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Clark <robdclark@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Steev Klimaszewski <steev@...i.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Stanislav Lisovskiy <stanislav.lisovskiy@...el.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 01/12] drm/bridge: Fix the stop condition of
 drm_bridge_chain_pre_enable()

Hi Doug,

On Wed, Apr 14, 2021 at 06:19:13PM -0700, Doug Anderson wrote:
> On Sun, Apr 4, 2021 at 5:50 PM Laurent Pinchart wrote:
> > On Fri, Apr 02, 2021 at 03:28:35PM -0700, Douglas Anderson wrote:
> > > The drm_bridge_chain_pre_enable() is not the proper opposite of
> > > drm_bridge_chain_post_disable(). It continues along the chain to
> > > _before_ the starting bridge. Let's fix that.
> > >
> > > Fixes: 05193dc38197 ("drm/bridge: Make the bridge chain a double-linked list")
> > > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> > > Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
> > > ---
> > >
> > > (no changes since v1)
> > >
> > >  drivers/gpu/drm/drm_bridge.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> > > index 64f0effb52ac..044acd07c153 100644
> > > --- a/drivers/gpu/drm/drm_bridge.c
> > > +++ b/drivers/gpu/drm/drm_bridge.c
> > > @@ -522,6 +522,9 @@ void drm_bridge_chain_pre_enable(struct drm_bridge *bridge)
> > >       list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
> > >               if (iter->funcs->pre_enable)
> > >                       iter->funcs->pre_enable(iter);
> > > +
> > > +             if (iter == bridge)
> > > +                     break;
> >
> > This looks good as it matches drm_atomic_bridge_chain_disable().
> >
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> 
> Thanks for your review here and several of the other patches. Can you
> suggest any plan for getting them landed? It would at least be nice to
> get the non-controversial ones landed.

Do you have commit access to drm-misc ? If not, given your
contributions, I think you qualify for it.

> > I'm curious though, given that the bridge passed to the function should
> > be the one closest to the encoder, does this make a difference ?
> 
> Yes, that's how I discovered it originally. Let's see. So if I don't
> have this patch but have the rest of the series then I get a splat at
> bootup. This shows that dsi_mgr_bridge_pre_enable() must be "earlier"
> in the chain than my bridge chip. Here's the splat:

Right, I think it's caused by a later patch in the series calling this
function with a different bridge than the one closest to the encoder.

>  msm_dsi_host_get_phy_clk_req: unable to calc clk rate, -22
>  ------------[ cut here ]------------
>  disp_cc_mdss_ahb_clk status stuck at 'off'
>  WARNING: CPU: 7 PID: 404 at drivers/clk/qcom/clk-branch.c:92
> clk_branch_toggle+0x194/0x280
>  Modules linked in: joydev
>  CPU: 7 PID: 404 Comm: frecon Tainted: G    B             5.12.0-rc3-lockdep+ #2
>  Hardware name: Google Lazor (rev1 - 2) with LTE (DT)
>  pstate: 60400089 (nZCv daIf +PAN -UAO -TCO BTYPE=--)
>  pc : clk_branch_toggle+0x194/0x280
>  lr : clk_branch_toggle+0x190/0x280
>  ...
>  Call trace:
>   clk_branch_toggle+0x194/0x280
>   clk_branch2_enable+0x28/0x34
>   clk_core_enable+0x2f4/0x6b4
>   clk_enable+0x54/0x74
>   dsi_phy_enable_resource+0x80/0xd8
>   msm_dsi_phy_enable+0xa8/0x4a8
>   enable_phy+0x9c/0xf4
>   dsi_mgr_bridge_pre_enable+0x23c/0x4b0
>   drm_bridge_chain_pre_enable+0xac/0xe4
>   ti_sn_bridge_connector_get_modes+0x134/0x1b8
>   drm_helper_probe_single_connector_modes+0x49c/0x1358
>   drm_mode_getconnector+0x460/0xe98
>   drm_ioctl_kernel+0x144/0x228
>   drm_ioctl+0x418/0x7cc
>   drm_compat_ioctl+0x1bc/0x230
>   __arm64_compat_sys_ioctl+0x14c/0x188
>   el0_svc_common+0x128/0x23c
>   do_el0_svc_compat+0x50/0x60
>   el0_svc_compat+0x24/0x34
>   el0_sync_compat_handler+0xc0/0xf0
>   el0_sync_compat+0x174/0x180

-- 
Regards,

Laurent Pinchart