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Message-ID: <CAMuHMdUi7pf1YfKRjMv_7VuKwjR5XekRXfcEzuPScGzHraGjyQ@mail.gmail.com>
Date: Fri, 30 May 2025 09:55:37 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Jayesh Choudhary <j-choudhary@...com>
Cc: dianders@...omium.org, andrzej.hajda@...el.com, neil.armstrong@...aro.org,
rfoss@...nel.org, Laurent.pinchart@...asonboard.com,
dri-devel@...ts.freedesktop.org, tomi.valkeinen@...asonboard.com,
max.krummenacher@...adex.com, ernestvanhoecke@...il.com, jonas@...boo.se,
jernej.skrabec@...il.com, maarten.lankhorst@...ux.intel.com,
mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com, simona@...ll.ch,
kieran.bingham+renesas@...asonboard.com, linux-kernel@...r.kernel.org,
max.oss.09@...il.com, devarsht@...com, Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v3] drm/bridge: ti-sn65dsi86: Add HPD for DisplayPort
connector type
Hi Jayesh,
CC devicetree
On Fri, 30 May 2025 at 04:54, Jayesh Choudhary <j-choudhary@...com> wrote:
> On 29/05/25 16:34, Jayesh Choudhary wrote:
> > By default, HPD was disabled on SN65DSI86 bridge. When the driver was
> > added (commit "a095f15c00e27"), the HPD_DISABLE bit was set in pre-enable
> > call which was moved to other function calls subsequently.
> > Later on, commit "c312b0df3b13" added detect utility for DP mode. But with
> > HPD_DISABLE bit set, all the HPD events are disabled[0] and the debounced
> > state always return 1 (always connected state).
> >
> > Set HPD_DISABLE bit conditionally based on "no-hpd" property.
> > Since the HPD_STATE is reflected correctly only after waiting for debounce
> > time (~100-400ms) and adding this delay in detect() is not feasible
> > owing to the performace impact (glitches and frame drop), remove runtime
> > calls in detect() and add hpd_enable()/disable() bridge hooks with runtime
> > calls, to detect hpd properly without any delay.
> >
> > [0]: <https://www.ti.com/lit/gpn/SN65DSI86> (Pg. 32)
> >
> > Fixes: c312b0df3b13 ("drm/bridge: ti-sn65dsi86: Implement bridge connector operations for DP")
> > Cc: Max Krummenacher <max.krummenacher@...adex.com>
> > Signed-off-by: Jayesh Choudhary <j-choudhary@...com>
> > ---
> >
> > Changelog v2->v3:
> > - Change conditional based on no-hpd property to address [1]
> > - Remove runtime calls in detect() with appropriate comments
> > - Add hpd_enable() and hpd_disable() in drm_bridge_funcs
> > - Not picking up "Tested-by" tag as there are new changes
> >
> > v2 patch link:
> > <https://lore.kernel.org/all/20250508115433.449102-1-j-choudhary@ti.com/>
> >
> > [1]: <https://lore.kernel.org/all/mwh35anw57d6nvre3sguetzq3miu4kd43rokegvul7fk266lys@5h2euthpk7vq/>
Thanks for your patch!
> > This would also require dts changes in all the nodes of sn65dsi86
> > to ensure that they have no-hpd property.
>
> DTS patch is posted now:
> <https://lore.kernel.org/all/20250529112423.484232-1-j-choudhary@ti.com/>
On all Renesas platforms handled by that patch, the DP bridge's HPD pin
is wired to the HPD pin on the mini-DP connector. What am I missing?
Regardless, breaking backwards-compatibility with existing DTBs is
definitely a no-go.
> > drivers/gpu/drm/bridge/ti-sn65dsi86.c | 40 +++++++++++++++++++++++----
> > 1 file changed, 35 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > index 60224f476e1d..e9ffc58acf58 100644
> > --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > @@ -190,6 +190,7 @@ struct ti_sn65dsi86 {
> > u8 ln_assign;
> > u8 ln_polrs;
> > bool comms_enabled;
> > + bool no_hpd;
> > struct mutex comms_mutex;
> >
> > #if defined(CONFIG_OF_GPIO)
> > @@ -352,8 +353,10 @@ static void ti_sn65dsi86_enable_comms(struct ti_sn65dsi86 *pdata,
> > * change this to be conditional on someone specifying that HPD should
> > * be used.
> > */
> > - regmap_update_bits(pdata->regmap, SN_HPD_DISABLE_REG, HPD_DISABLE,
> > - HPD_DISABLE);
> > +
> > + if (pdata->no_hpd)
> > + regmap_update_bits(pdata->regmap, SN_HPD_DISABLE_REG, HPD_DISABLE,
> > + HPD_DISABLE);
> >
> > pdata->comms_enabled = true;
> >
> > @@ -1195,9 +1198,17 @@ static enum drm_connector_status ti_sn_bridge_detect(struct drm_bridge *bridge)
> > struct ti_sn65dsi86 *pdata = bridge_to_ti_sn65dsi86(bridge);
> > int val = 0;
> >
> > - pm_runtime_get_sync(pdata->dev);
> > + /*
> > + * The chip won't report HPD right after being powered on as
> > + * HPD_DEBOUNCED_STATE reflects correct state only after the
> > + * debounce time (~100-400 ms).
> > + * So having pm_runtime_get_sync() and immediately reading
> > + * the register in detect() won't work, and adding delay()
> > + * in detect will have performace impact in display.
> > + * So remove runtime calls here.
> > + */
> > +
> > regmap_read(pdata->regmap, SN_HPD_DISABLE_REG, &val);
> > - pm_runtime_put_autosuspend(pdata->dev);
> >
> > return val & HPD_DEBOUNCED_STATE ? connector_status_connected
> > : connector_status_disconnected;
> > @@ -1220,6 +1231,20 @@ static void ti_sn65dsi86_debugfs_init(struct drm_bridge *bridge, struct dentry *
> > debugfs_create_file("status", 0600, debugfs, pdata, &status_fops);
> > }
> >
> > +static void ti_sn_bridge_hpd_enable(struct drm_bridge *bridge)
> > +{
> > + struct ti_sn65dsi86 *pdata = bridge_to_ti_sn65dsi86(bridge);
> > +
> > + pm_runtime_get_sync(pdata->dev);
> > +}
> > +
> > +static void ti_sn_bridge_hpd_disable(struct drm_bridge *bridge)
> > +{
> > + struct ti_sn65dsi86 *pdata = bridge_to_ti_sn65dsi86(bridge);
> > +
> > + pm_runtime_put_sync(pdata->dev);
> > +}
> > +
> > static const struct drm_bridge_funcs ti_sn_bridge_funcs = {
> > .attach = ti_sn_bridge_attach,
> > .detach = ti_sn_bridge_detach,
> > @@ -1234,6 +1259,8 @@ static const struct drm_bridge_funcs ti_sn_bridge_funcs = {
> > .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
> > .atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
> > .debugfs_init = ti_sn65dsi86_debugfs_init,
> > + .hpd_enable = ti_sn_bridge_hpd_enable,
> > + .hpd_disable = ti_sn_bridge_hpd_disable,
> > };
> >
> > static void ti_sn_bridge_parse_lanes(struct ti_sn65dsi86 *pdata,
> > @@ -1322,7 +1349,8 @@ static int ti_sn_bridge_probe(struct auxiliary_device *adev,
> > ? DRM_MODE_CONNECTOR_DisplayPort : DRM_MODE_CONNECTOR_eDP;
> >
> > if (pdata->bridge.type == DRM_MODE_CONNECTOR_DisplayPort)
> > - pdata->bridge.ops = DRM_BRIDGE_OP_EDID | DRM_BRIDGE_OP_DETECT;
> > + pdata->bridge.ops = DRM_BRIDGE_OP_EDID | DRM_BRIDGE_OP_DETECT |
> > + DRM_BRIDGE_OP_HPD;
> >
> > drm_bridge_add(&pdata->bridge);
> >
> > @@ -1935,6 +1963,8 @@ static int ti_sn65dsi86_probe(struct i2c_client *client)
> > return dev_err_probe(dev, PTR_ERR(pdata->refclk),
> > "failed to get reference clock\n");
> >
> > + pdata->no_hpd = of_property_read_bool(dev->of_node, "no-hpd");
> > +
> > pm_runtime_enable(dev);
> > pm_runtime_set_autosuspend_delay(pdata->dev, 500);
> > pm_runtime_use_autosuspend(pdata->dev);
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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