linux-kernel - Re: [PATCH v3 12/15] drm/bridge: Add ITE IT6263 LVDS to HDMI converter

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20241022-amazing-fresh-agouti-fb6eda@houat>
Date: Tue, 22 Oct 2024 10:15:19 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Liu Ying <victor.liu@....com>
Cc: dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org, imx@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, andrzej.hajda@...el.com, neil.armstrong@...aro.org, 
	rfoss@...nel.org, Laurent.pinchart@...asonboard.com, jonas@...boo.se, 
	jernej.skrabec@...il.com, airlied@...il.com, simona@...ll.ch, 
	maarten.lankhorst@...ux.intel.com, tzimmermann@...e.de, robh@...nel.org, krzk+dt@...nel.org, 
	conor+dt@...nel.org, quic_jesszhan@...cinc.com, mchehab@...nel.org, 
	shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de, 
	festevam@...il.com, catalin.marinas@....com, will@...nel.org, 
	sakari.ailus@...ux.intel.com, hverkuil@...all.nl, tomi.valkeinen@...asonboard.com, 
	quic_bjorande@...cinc.com, geert+renesas@...der.be, dmitry.baryshkov@...aro.org, 
	arnd@...db.de, nfraprado@...labora.com, thierry.reding@...il.com, 
	prabhakar.mahadev-lad.rj@...renesas.com, sam@...nborg.org, marex@...x.de, biju.das.jz@...renesas.com
Subject: Re: [PATCH v3 12/15] drm/bridge: Add ITE IT6263 LVDS to HDMI
 converter

On Tue, Oct 22, 2024 at 04:10:51PM +0800, Liu Ying wrote:
> Hi Maxime,
> 
> On 10/22/2024, Maxime Ripard wrote:
> > On Tue, Oct 22, 2024 at 03:36:47PM +0800, Liu Ying wrote:
> >> Hi Maxime,
> >>
> >> On 10/21/2024, Maxime Ripard wrote:
> >>> On Mon, Oct 21, 2024 at 02:44:43PM +0800, Liu Ying wrote:
> >>>> +static int it6263_bridge_atomic_check(struct drm_bridge *bridge,
> >>>> +				      struct drm_bridge_state *bridge_state,
> >>>> +				      struct drm_crtc_state *crtc_state,
> >>>> +				      struct drm_connector_state *conn_state)
> >>>> +{
> >>>> +	struct drm_display_mode *mode = &crtc_state->adjusted_mode;
> >>>> +	int ret;
> >>>> +
> >>>> +	ret = drm_atomic_helper_connector_hdmi_check(conn_state->connector,
> >>>> +						     conn_state->state);
> >>>> +	if (ret)
> >>>> +		return ret;
> >>>> +
> >>>> +	return mode->clock > MAX_PIXEL_CLOCK_KHZ ? -EINVAL : 0;
> >>>
> >>> drm_atomic_helper_connector_hdmi_check will already make that check, so
> >>> it's redundant.
> >>
> >> MAX_PIXEL_CLOCK_KHZ is 150MHz. With 150MHz pixel clock rate, we'll get
> >> 150MHz HDMI character rate for 8bpc and 187.5MHz HDMI character rate
> >> for 10bpc, both are lower than MAX_HDMI_TMDS_CHAR_RATE_HZ = 225MHz.
> > 
> > I guess? I have no idea how that's relevant though. Where are those
> > constraints coming from, and why aren't you checking for them in
> > tmds_char_rate_valid?
> 
> All constraints come from IT6263 data sheet. They are also mentioned
> in IT6263 product link(commit message contains the link).
> 
> https://www.ite.com.tw/en/product/cate1/IT6263
> 
> "
> LVDS RX
> Support input clock rate up to 150 MHz
> 
> HDMI TX
> Support link speeds of up to 2.25 Gbps (link clock rate of 225 MHz) 
> "
> 
> If no objection, I'll check mode clock rate against
> MAX_PIXEL_CLOCK_KHZ in tmds_char_rate_valid.

If you don't support bpc other than 8, and no other format than RGB,
then it's a good enough approximation.

It should be documented though

Maxime

Download attachment "signature.asc" of type "application/pgp-signature" (274 bytes)