Re: Question: Re: [PATCH] drm/bridge: analogix: protect power when get_modes or detect

[Mark yao <mark.yao@xxxxxxxxxxxxxx>]

On 2016年10月12日 22:51, Sean Paul wrote:
> On Wed, Oct 12, 2016 at 6:22 AM, Mark yao <mark.yao@xxxxxxxxxxxxxx> wrote:
> > I'm not familiar with the analogix driver, maybe use a power reference count
> > would better then direct power on/off analogix_dp.
> >
> > Does anyone has the idea to protect detect and get_modes context?
> I'm not sure a reference count is going to help here. The common
> pattern is to call detect() followed by get_modes() and then modeset.
> However, it's not guaranteed that any one of those functions will be
> called after the other. So, if you leave things on after detect or
> get_modes, you might be wasting power (or worse).
>
> I recently ran into this exact problem with a panel we're using. Check
> out "0b8b059a7: drm/bridge: analogix_dp: Ensure the panel is properly
> prepared/unprepared". Perhaps you can piggyback on that function to
> add your pm_runtime and plat_data callbacks (since using dpms_mode
> might be racey).
>
> Sean
Hi Sean

Thanks for your advice.

I re-test the detect and get_modes, only use pm_runtime_get/put also can 
fix my problem.
without plat_data callbacks can avoid race to dpms_mode.

I had send v2 patch,  you can review it.

Thanks.

> > I found many other connector driver also direct access register on detect or
> > get_modes, no problem for it?
> >
> > On 2016年10月12日 18:00, Mark Yao wrote:
> >
> > The drm callback ->detect and ->get_modes seems is not power safe,
> > they may be called when device is power off, do register access on
> > detect or get_modes will cause system die.
> >
> > Here is the path call ->detect before analogix_dp power on
> > [<ffffff800843babc>] analogix_dp_detect+0x44/0xdc
> > [<ffffff80083fd840>]
> > drm_helper_probe_single_connector_modes_merge_bits+0xe8/0x41c
> > [<ffffff80083fdb84>] drm_helper_probe_single_connector_modes+0x10/0x18
> > [<ffffff8008418d24>] drm_mode_getconnector+0xf4/0x304
> > [<ffffff800840cff0>] drm_ioctl+0x23c/0x390
> > [<ffffff80081a8adc>] do_vfs_ioctl+0x4b8/0x58c
> > [<ffffff80081a8c10>] SyS_ioctl+0x60/0x88
> >
> > Cc: Inki Dae <inki.dae@xxxxxxxxxxx>
> > Cc: Sean Paul <seanpaul@xxxxxxxxxxxx>
> > Cc: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> > Cc: "Ville Syrjälä" <ville.syrjala@xxxxxxxxxxxxxxx>
> >
> > Signed-off-by: Mark Yao <mark.yao@xxxxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/bridge/analogix/analogix_dp_core.c | 28
> > ++++++++++++++++++++++
> >   1 file changed, 28 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > index efac8ab..09dece2 100644
> > --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> > @@ -1062,6 +1062,13 @@ int analogix_dp_get_modes(struct drm_connector
> > *connector)
> >    return 0;
> >    }
> >
> > + if (dp->dpms_mode != DRM_MODE_DPMS_ON) {
> > + pm_runtime_get_sync(dp->dev);
> > +
> > + if (dp->plat_data->power_on)
> > + dp->plat_data->power_on(dp->plat_data);
> > + }
> > +
> >    if (analogix_dp_handle_edid(dp) == 0) {
> >    drm_mode_connector_update_edid_property(&dp->connector, edid);
> >    num_modes += drm_add_edid_modes(&dp->connector, edid);
> > @@ -1073,6 +1080,13 @@ int analogix_dp_get_modes(struct drm_connector
> > *connector)
> >    if (dp->plat_data->get_modes)
> >    num_modes += dp->plat_data->get_modes(dp->plat_data, connector);
> >
> > + if (dp->dpms_mode != DRM_MODE_DPMS_ON) {
> > + if (dp->plat_data->power_off)
> > + dp->plat_data->power_off(dp->plat_data);
> > +
> > + pm_runtime_put_sync(dp->dev);
> > + }
> > +
> >    ret = analogix_dp_prepare_panel(dp, false, false);
> >    if (ret)
> >    DRM_ERROR("Failed to unprepare panel (%d)\n", ret);
> > @@ -1106,9 +1120,23 @@ analogix_dp_detect(struct drm_connector *connector,
> > bool force)
> >    return connector_status_disconnected;
> >    }
> >
> > + if (dp->dpms_mode != DRM_MODE_DPMS_ON) {
> > + pm_runtime_get_sync(dp->dev);
> > +
> > + if (dp->plat_data->power_on)
> > + dp->plat_data->power_on(dp->plat_data);
> > + }
> > +
> >    if (!analogix_dp_detect_hpd(dp))
> >    status = connector_status_connected;
> >
> > + if (dp->dpms_mode != DRM_MODE_DPMS_ON) {
> > + if (dp->plat_data->power_off)
> > + dp->plat_data->power_off(dp->plat_data);
> > +
> > + pm_runtime_put_sync(dp->dev);
> > + }
> > +
> >    ret = analogix_dp_prepare_panel(dp, false, false);
> >    if (ret)
> >    DRM_ERROR("Failed to unprepare panel (%d)\n", ret);
> >
> >
> >
> > --
> > Ｍark Yao


--
Ｍark Yao


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