From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755933AbdESSYq convert rfc822-to-8bit (ORCPT ); Fri, 19 May 2017 14:24:46 -0400 Received: from mailoutvs6.siol.net ([213.250.19.133]:42597 "EHLO mail.siol.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754839AbdESSXh (ORCPT ); Fri, 19 May 2017 14:23:37 -0400 From: Jernej =?utf-8?B?xaBrcmFiZWM=?= To: linux-sunxi@googlegroups.com, icenowy@aosc.io Cc: Maxime Ripard , Rob Herring , Chen-Yu Tsai , dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org Subject: Re: [linux-sunxi] Re: [RFC PATCH 07/11] drm: sun4i: add support for the TV encoder in H3 SoC Date: Fri, 19 May 2017 20:23:32 +0200 Message-ID: <1958057.WDKm0nQKgW@jernej-laptop> In-Reply-To: <3FCDBC05-20A1-460C-A21B-8C3E9C776768@aosc.io> References: <20170517164354.16399-1-icenowy@aosc.io> <20170519180330.7hpfkdqk3r2x3kn5@flea.home> <3FCDBC05-20A1-460C-A21B-8C3E9C776768@aosc.io> MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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. Best regards, Jernej