Re: [PATCH v17 4/8] drm: bridge: Cadence: Add MHDP8501 DP/HDMI driver

[Maxime Ripard]

On Sun, Sep 29, 2024 at 02:34:36AM GMT, Sandor Yu wrote:
> > > +static void cdns_hdmi_sink_config(struct cdns_mhdp8501_device *mhdp)
> > > +{
> > > +	struct drm_display_info *display = &mhdp->curr_conn->display_info;
> > > +	struct drm_connector_state *conn_state = mhdp->curr_conn->state;
> > 
> > That looks a bit hackish to me. We should probably provide a helper to get the
> > connector state the bridge is attached to.
> 
> How about code change to followed, is it more clear?
> 370         struct drm_connector *connector = mhdp->curr_conn;
> 371         struct drm_connector_state *conn_state = connector->state;
> 372         struct drm_display_info *display = &connector->display_info;
> 373         struct drm_scdc *scdc = &display->hdmi.scdc;

What I meant was that I wish bridges had a way to get their connector
pointer. It doesn't look like it's possible with drm_bridge_connector,
and we don't have access to drm_display_info anymore.

I don't really see a good way to do this yet, so maybe that kind of
workaround is ok. Eventually, I guess we'll have the scrambler setup in
the HDMI connector helpers anyway.

Dmitry, any idea?

> > > +static enum drm_mode_status
> > > +cdns_hdmi_tmds_char_rate_valid(const struct drm_bridge *bridge,
> > > +			       const struct drm_display_mode *mode,
> > > +			       unsigned long long tmds_rate) {
> > > +	struct cdns_mhdp8501_device *mhdp = bridge->driver_private;
> > > +	union phy_configure_opts phy_cfg;
> > > +	int ret;
> > > +
> > > +	phy_cfg.hdmi.tmds_char_rate = tmds_rate;
> > > +
> > > +	ret = phy_validate(mhdp->phy, PHY_MODE_HDMI, 0, &phy_cfg);
> > > +	if (ret < 0)
> > > +		return MODE_CLOCK_RANGE;
> > > +
> > > +	return MODE_OK;
> > > +}
> > > +
> > > +static enum drm_mode_status
> > > +cdns_hdmi_bridge_mode_valid(struct drm_bridge *bridge,
> > > +			    const struct drm_display_info *info,
> > > +			    const struct drm_display_mode *mode) {
> > > +	unsigned long long tmds_rate;
> > > +
> > > +	/* We don't support double-clocked and Interlaced modes */
> > > +	if (mode->flags & DRM_MODE_FLAG_DBLCLK ||
> > > +	    mode->flags & DRM_MODE_FLAG_INTERLACE)
> > > +		return MODE_BAD;
> > > +
> > > +	if (mode->hdisplay > 3840)
> > > +		return MODE_BAD_HVALUE;
> > > +
> > > +	if (mode->vdisplay > 2160)
> > > +		return MODE_BAD_VVALUE;
> > > +
> > > +	tmds_rate = mode->clock * 1000ULL;
> > > +	return cdns_hdmi_tmds_char_rate_valid(bridge, mode, tmds_rate); }
> > 
> > Didn't we agree on creating a mode_valid helper?
> 
> In fact, now I'm no idea where should add the mode_valid helper function.
> 
> In struct drm_bridge_funcs, it had mode_valid() and hdmi_tmds_char_rate_valid().
> 
> If create a new mode_valid helper function in struct drm_connector_hdmi_funcs,
> Is it appropriate to call another API function(tmds_char_rate_valid)
> at the same level within this API function?

I'm not quite sure what you mean, but a reasonable approach to me would
be to turn drm_hdmi_state_helper.c hdmi_clock_valid into a public
function, and then call it from drm_bridge_connector mode_valid hook.

It's a similar discussion to the previous one really: in order to
implement it properly, we need access to drm_display_info.

Maxime

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