Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752017AbdGUGcf (ORCPT ); Fri, 21 Jul 2017 02:32:35 -0400 Received: from mailgw02.mediatek.com ([210.61.82.184]:13483 "EHLO mailgw02.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751479AbdGUGcc (ORCPT ); Fri, 21 Jul 2017 02:32:32 -0400 Message-ID: <1500618746.14868.13.camel@mtksdaap41> Subject: Re: [PATCH v4 2/2] arm64: dts: Add Mediatek SoC MT2712 and evaluation board dts and Makefile From: YT Shen To: Matthias Brugger CC: Rob Herring , Mark Rutland , Thomas Gleixner , Jason Cooper , Marc Zyngier , Greg Kroah-Hartman , Catalin Marinas , Will Deacon , Mars Cheng , , , , , , Date: Fri, 21 Jul 2017 14:32:26 +0800 In-Reply-To: References: <1498123975-9748-1-git-send-email-yt.shen@mediatek.com> <1498123975-9748-3-git-send-email-yt.shen@mediatek.com> <1500446884.14021.12.camel@mtksdaap41> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-MTK: N Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2547 Lines: 87 On Wed, 2017-07-19 at 11:26 +0200, Matthias Brugger wrote: > > On 07/19/2017 08:48 AM, YT Shen wrote: > > On Tue, 2017-07-18 at 18:29 +0200, Matthias Brugger wrote: > >> > >> On 06/22/2017 11:32 AM, YT Shen wrote: > >>> This adds basic chip support for Mediatek 2712 > > [...] > > >>> + > >>> + uart_clk: dummy26m { > >>> + compatible = "fixed-clock"; > >>> + clock-frequency = <26000000>; > >>> + #clock-cells = <0>; > >>> + }; > >>> + > > [...] > > >>> + > >>> + soc { > >>> + #address-cells = <2>; > >>> + #size-cells = <2>; > >>> + compatible = "simple-bus"; > >>> + ranges; > >>> + > >>> + uart5: serial@1000f000 { > >>> + compatible = "mediatek,mt2712-uart", > >>> + "mediatek,mt6577-uart"; > >>> + reg = <0 0x1000f000 0 0x400>; > >>> + interrupts = ; > >>> + clocks = <&uart_clk>, <&uart_clk>; > >>> + clock-names = "baud", "bus"; > >>> + status = "disabled"; > >>> + }; > >> > >> So baud and bus clock are both 26 MHz? > > We didn't have CCF clock support in this series. > > After we have clock source support, we could use the correct clocks to > > the UARTs and drop the 26MHz fixed rate UART clock. > > > > The bus clock is 26MHz. The baud clock could be from another clock > > source, using the same 26MHz fixed clock works also. > > > > > > [1] https://patchwork.kernel.org/patch/9670877/ > > [2] https://patchwork.kernel.org/patch/6436021/ > > > > Yes, just using one 26 MHz clock works, but it uses an deprecated > binding, so we should not do this, as through copying from the source of > other SoCs we will keep it alive forever. Anyway that's not your case, > as you defined the two clocks. > > The device tree should reflect the HW, that's why I asked for the clock > frequency of both clocks. I searched the git history and it was never > done right before. So you could be the first :) > > Thanks, > Matthias Ok, I want to make it clear. The following example baud_clk: dummy26m { compatible = "fixed-clock"; clock-frequency = <26000000>; #clock-cells = <0>; }; sys_clk: dummyclk { compatible = "fixed-clock"; clock-frequency = <26000000>; #clock-cells = <0>; }; uart0: serial@11002000 { [...] clocks = <&baud_clk>, <&sys_clk>; [...] } Do you think it is clear to reflect the HW that the baud clock and sys clock can be different source or we need to choose another frequency? Thanks. yt.shen