Re: [PATCH v3 01/12] drm/bridge: Fix the stop condition of drm_bridge_chain_pre_enable()

Doug Anderson
2021-04-15T01:19:42Z

Hi,

On Sun, Apr 4, 2021 at 5:50 PM Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>
> Hi Doug,
>
> Thank you for the patch.
>
> 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@chromium.org>
> > Reviewed-by: Andrzej Hajda <a.hajda@samsung.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@ideasonboard.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.

> 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:

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