From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759722AbcHENXr (ORCPT ); Fri, 5 Aug 2016 09:23:47 -0400 Received: from regular1.263xmail.com ([211.150.99.130]:45925 "EHLO regular1.263xmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758060AbcHENXq (ORCPT ); Fri, 5 Aug 2016 09:23:46 -0400 X-263anti-spam: KSV:0; X-MAIL-GRAY: 0 X-MAIL-DELIVERY: 1 X-KSVirus-check: 0 X-ABS-CHECKED: 4 X-ADDR-CHECKED: 0 X-RL-SENDER: zhengxing@rock-chips.com X-FST-TO: heiko@sntech.de X-SENDER-IP: 103.29.142.67 X-LOGIN-NAME: zhengxing@rock-chips.com X-UNIQUE-TAG: <7853e96bf2ca04d24617b3754e97304f> X-ATTACHMENT-NUM: 0 X-DNS-TYPE: 0 Message-ID: <57A49342.3020309@rock-chips.com> Date: Fri, 05 Aug 2016 21:23:14 +0800 From: Xing Zheng User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120410 Thunderbird/11.0.1 MIME-Version: 1.0 To: =?UTF-8?B?SGVpa28gU3TDvGJuZXI=?= CC: mturquette@baylibre.com, sboyd@codeaurora.org, linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org, dianders@chromium.org, briannorris@chromium.org, huangtao@rock-chips.com, zhangqing@rock-chips.com Subject: Re: [PATCH v3 7/7] clk: rockchip: rk3399: Add support frac mode frequencies References: <1470122401-31934-1-git-send-email-zhengxing@rock-chips.com> <12790025.3tRiQgk9GG@diego> <57A3F971.6000009@rock-chips.com> <1786762.HqNHoLusdi@diego> In-Reply-To: <1786762.HqNHoLusdi@diego> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Heiko, On 2016年08月05日 16:48, Heiko Stübner wrote: > Hi Xing, > > Am Freitag, 5. August 2016, 10:26:57 schrieb Xing Zheng: >> On 2016年08月05日 03:19, Heiko Stübner wrote: >>> Am Dienstag, 2. August 2016, 15:22:59 schrieb Xing Zheng: >>>> We need to support various display resolutions for external >>>> display devices like HDMI/DP, the frac mode can help us to >>>> acquire almost any frequencies, and need higher VCOs to reduce >>>> clock jitters. >>>> >>>> Signed-off-by: Xing Zheng >>> why does this need to be a separate rate array and cannot live in the >>> general pll rate array? >>> >>> The plls are general purpose, so we shouldn't limit them arbitarily. >> Yes, I understand your mean. :-) >> >>> I currently only see some frequencies (594MHz, 297MHz, 54MHz) that are >>> present in both arrays but have different settings. As your patch >>> description says that these settings reduce clock jitter, wouldn't the >>> general frequencies also profit from merging these new values into the >>> general rate array? >> and here are some of our ideas: >> >> "WIth the frac mode and higher VCO to reduce clock jitters" that >> suggestion is from IC designer. >> There are many and various kinds resolution and needed frequencies for >> external disaplay devices. For example, the DP needs: >> 3840x2160 533250KHz >> 3840x2160 297000KHz >> 3840x2160 296703KHz >> 2560x1440 241500KHz >> 1920x1080 148500KHz >> 1920x1080 148352KHz >> 1680x1050 146250KHz >> 1600x900 108000KHz >> 1280x1024 135000KHz >> 1280x1024 108000KHz >> ... and so on >> >> There some frequencies must be allocated with frac mode. We separate >> these frequencies that are only used for display (VPLL) from the general >> rate table, and put them to be classified into a frac mode table, we can >> reduce the frequency of the query time, the two rate tables will not >> interfere with each other. Because other PLLs don't need to assgin these >> various frequencies with frac mode. > Hmm, you're adding 14 frequencies to that new table (4 or so of them > duplicating existing frequencies). So even if the effective number of new > frequencies goes from now 10 to 20, I don't think walking that table will take > an excessive time longer than now. > > After the patch introducing the automatic rate calculation, the rate table we > need to walk, will even get smaller. > > Other components might also profit from the updated standard frequencies with > less jitter you're introducing here. > > And of course there is also the possibility somebody might want to build some > rk3399 device without any graphics output at all [arm-server seem to be the > new hype :-) ], so may want to use the vpll for something else completely. > > So I still don't see an argument why it needs to be a separate table, as I > currently don't see a case were it will really hurt the other PLLs. > > > Heiko > Yes, sorry to this idea is not comprehensive. I will try to find a better way. Thanks for your comments. :-) -- - Xing Zheng