From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932715AbcECC1q (ORCPT ); Mon, 2 May 2016 22:27:46 -0400 Received: from mail-pa0-f54.google.com ([209.85.220.54]:33252 "EHLO mail-pa0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932239AbcECC1o (ORCPT ); Mon, 2 May 2016 22:27:44 -0400 Subject: Re: [PATCH 4/9] thermal: rockchip: handle the power sequence for tsadc controller To: Eduardo Valentin References: <1460950562-20652-1-git-send-email-wxt@rock-chips.com> <1460950562-20652-5-git-send-email-wxt@rock-chips.com> <20160427234818.GB2590@localhost.localdomain> <57216C65.5040501@gmail.com> <20160428150432.GA20009@localhost.localdomain> Cc: Caesar Wang , Heiko Stuebner , linux-pm@vger.kernel.org, dianders@chromium.org, linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org, smbarber@google.com, briannorris@google.com, Zhang Rui , linux-arm-kernel@lists.infradead.org From: Caesar Wang Message-ID: <57280C8E.5080406@gmail.com> Date: Tue, 3 May 2016 10:27:26 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: <20160428150432.GA20009@localhost.localdomain> 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 在 2016年04月28日 23:04, Eduardo Valentin 写道: > On Thu, Apr 28, 2016 at 09:50:29AM +0800, Caesar Wang wrote: >> >> 在 2016年04月28日 07:48, Eduardo Valentin 写道: >>> On Mon, Apr 18, 2016 at 11:35:56AM +0800, Caesar Wang wrote: >>>> + regmap_write(grf, GRF_TSADC_TESTBIT_L, GRF_TSADC_TSEN_PD_ON); >>>> + mdelay(10); >>>> + regmap_write(grf, GRF_TSADC_TESTBIT_L, GRF_TSADC_TSEN_PD_OFF); >>>> + udelay(100); /* The spec note says at least 15 us */ >>>> + regmap_write(grf, GRF_SARADC_TESTBIT, GRF_SARADC_TESTBIT_ON); >>>> + regmap_write(grf, GRF_TSADC_TESTBIT_H, GRF_TSADC_TESTBIT_H_ON); >>>> + udelay(200); /* The spec note says at least 90 us */ >>> Does it make sense to use usleep_range() instead? >> I think so in the past, but I'm digging into the the udelay/usleep for >> kernel. > What do you mean by in the past? timekeeping doc still recommends the > range 10us to 20ms for usleep_range() > >> In general, >> >> udelay < 10us ~100us >> mdelay > 1m, <1000ms/HZ >> usleep_range(min,max) > 100us, <20ms > even here, your udelays could be replaced by usleep_range(). > > Any particular reason you believe spining is better than sleeping in > your case? > >> msleep > 20ms, < 1000ms >> >> So the udelay is suit for tsadc power sequence. >> --- >> >> >> Also, we have used the mdelay(10), so it doesn't matter if use the udelay. >> After all the udelay is stable than the usleep_range. > What do you mean udelay is stable than usleep_range? usleep_range will > give the opportunity to the scheduler to coalesce wakeups. udelay is a > busyloop spin. Besides, I am not sure the current situation, but > busylooping may be affected by cpu frequency. Okay, thanks for pointing out. Send the fixes patch on https://patchwork.kernel.org/patch/8999971/ Thank you! -Caesar > >> -Caesar >> >>> 1.9.1 >>> >>> >>> >>> >>> -- >>> Thanks, >>> Caesar > _______________________________________________ > Linux-rockchip mailing list > Linux-rockchip@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-rockchip -- Thanks, Caesar