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
| ||
|
Date: Thu, 18 Aug 2022 17:56:35 +0200 From: Geert Uytterhoeven <geert@...ux-m68k.org> To: Maxime Ripard <maxime@...no.tech> Cc: Jernej Skrabec <jernej.skrabec@...il.com>, Martin Blumenstingl <martin.blumenstingl@...glemail.com>, Chen-Yu Tsai <wens@...e.org>, Philipp Zabel <p.zabel@...gutronix.de>, Jerome Brunet <jbrunet@...libre.com>, Samuel Holland <samuel@...lland.org>, Thomas Zimmermann <tzimmermann@...e.de>, Daniel Vetter <daniel@...ll.ch>, Emma Anholt <emma@...olt.net>, David Airlie <airlied@...ux.ie>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Noralf Trønnes <noralf@...nnes.org>, Kevin Hilman <khilman@...libre.com>, Neil Armstrong <narmstrong@...libre.com>, linux-sunxi@...ts.linux.dev, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Phil Elwell <phil@...pberrypi.com>, Mateusz Kwiatkowski <kfyatek+publicgit@...il.com>, Linux ARM <linux-arm-kernel@...ts.infradead.org>, Dave Stevenson <dave.stevenson@...pberrypi.com>, "open list:ARM/Amlogic Meson..." <linux-amlogic@...ts.infradead.org>, DRI Development <dri-devel@...ts.freedesktop.org>, Dom Cobley <dom@...pberrypi.com> Subject: Re: [PATCH v1 04/35] drm/modes: Introduce 480i and 576i modes Hi Maxime, On Thu, Aug 18, 2022 at 5:46 PM Maxime Ripard <maxime@...no.tech> wrote: > On Thu, Aug 18, 2022 at 05:34:30PM +0200, Geert Uytterhoeven wrote: > > On Thu, Aug 18, 2022 at 3:42 PM Maxime Ripard <maxime@...no.tech> wrote: > > > I started adding more sanity checks to my code, and I just realised I > > > don't seem to be able to reach 720 pixels over a single line though. If > > > I understood it properly, and according to [1] the active part of a line > > > is supposed to be 51.95us, and the blanking period taking 12.05us. [2] > > > in the timing section has pretty much the same numbers, so it looks > > > sane. > > > > > > At 13.5Mhz, a pixel is going to take roughly 74ns, and 51950 / 74 = 702 > > > pixels > > > > > > It seems we can go push it to 52350 ns, but that still gives us only 706 > > > pixels. > > > > > > Similarly, if I just choose to ignore that limit and just take the > > > active time I need, 720 * 74 = 53280ns > > > > > > That leaves us 10720ns for the blanking period, and that's not enough to > > > fit even the minimum of the front porch, hsync and back porch (1.55 + > > > 4.5 + 5.5 = 11.55us). > > > > > > Are those constraints merely recommendations, or am I missing something? > > > > You are missing that the parts near the borders of the full image are > > part of the overscan range, and may or may not be visible, depending > > on your actual display. > > The full 768x576 image size from BT.656 is not visible on a typical PAL display, > > and is more of an "absolute maximum rating", guaranteed to cover more > > than analog PAL. > > So the overscan range is not part of the active area, unlike what HDMI > is doing for example? Indeed. DVI-D and HDMI etc. are pure digital (let's ignore they are a digitized variant of old analog VGA ;-), hence there is a one-to-one match between pixels in the image and pixels on the screen (ignoring scaling). But even when using an analog VGA input on a modern digital display, you have controls to e.g. move the image. > Is there some minimal timings available somewhere to fit those absolute > maximum ratings? I guess they can be found on the Internet... 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
Powered by blists - more mailing lists