On Sat, May 20, 2017 at 2:23 AM, Jernej Škrabec <jernej.skrabec@xxxxxxxx> wrote: > Hi, > > Dne petek, 19. maj 2017 ob 20:08:18 CEST je Icenowy Zheng napisal(a): >> 于 2017年5月20日 GMT+08:00 上午2:03:30, Maxime Ripard <maxime.ripard@free- > electrons.com> 写到: >> >On Thu, May 18, 2017 at 12:43:50AM +0800, Icenowy Zheng wrote: >> >> Allwinner H3 features a TV encoder similar to the one in earlier >> > >> >SoCs, >> > >> >> but with some different points about clocks: >> >> - It has a mod clock and a bus clock. >> >> - The mod clock must be at a fixed rate to generate signal. >> > >> >Why? >> >> It's experiment result by Jernej. >> >> The clock rates in BSP kernel is also specially designed >> (PLL_DE at 432MHz) in order to be able to feed the TVE. > > My experiments and search through BSP code showed that TVE seems to have > additional fixed predivider 8. So if you want to generate 27 MHz clock, unit > has to be feed with 216 MHz. > > TVE has only one PLL source PLL_DE. And since 216 MHz is a bit low for DE2, > BSP defaults to 432 MHz for PLL_DE and use divider 2 to generate 216 MHz. This > clock is then divided by 8 internaly to get final 27 MHz. > > Please note that I don't have any hard evidence to support that, only > experimental data. However, only that explanation make sense to me. > > BTW, BSP H3/H5 TV driver supports only PAL and NTSC which both use 27 MHz base > clock. Further experiments are needed to check if there is any possibility to > have other resolutions by manipulating clocks and give other proper settings. > I plan to do that, but not in very near future. You only have composite video output, and those are the only 2 standard resolutions that make any sense. ChenYu -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
