From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 76BAAC433E6 for ; Mon, 1 Mar 2021 08:47:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4D93C64DE0 for ; Mon, 1 Mar 2021 08:47:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233498AbhCAIre (ORCPT ); Mon, 1 Mar 2021 03:47:34 -0500 Received: from z11.mailgun.us ([104.130.96.11]:19878 "EHLO z11.mailgun.us" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233456AbhCAIqp (ORCPT ); Mon, 1 Mar 2021 03:46:45 -0500 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1614588348; h=Message-ID: References: In-Reply-To: Subject: Cc: To: From: Date: Content-Transfer-Encoding: Content-Type: MIME-Version: Sender; bh=Cey4WVl7LtaCP6MJNq4HJn9FVmHktZGEEAE5nLQ/M8A=; b=msX9yDzfT02Z7rRyMhfib8r0n4Lfa3NDw3tpSA9FRrZUFzG0yF4s9bqq5UL0pU/8RCNDLCuH TQ6kcwh03FGvP6rlM3yFBjXaAHmMCLFkXpGs3Np83hqJyNY0eYiIxxrCoCK/tjNRFtw6TPBq iqDShotS/dqqEkX4YVu7zPQGdl0= X-Mailgun-Sending-Ip: 104.130.96.11 X-Mailgun-Sid: WyI4YmIzMiIsICJsaW51eC1mYmRldkB2Z2VyLmtlcm5lbC5vcmciLCAiYmU5ZTRhIl0= Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n03.prod.us-west-2.postgun.com with SMTP id 603ca9997aa94c52e7f31703 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Mon, 01 Mar 2021 08:45:13 GMT Sender: kgunda=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id C8F33C43463; Mon, 1 Mar 2021 08:45:13 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: kgunda) by smtp.codeaurora.org (Postfix) with ESMTPSA id EA03EC43462; Mon, 1 Mar 2021 08:45:12 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 01 Mar 2021 14:15:12 +0530 From: kgunda@codeaurora.org To: Daniel Thompson Cc: bjorn.andersson@linaro.org, jingoohan1@gmail.com, lee.jones@linaro.org, b.zolnierkie@samsung.com, dri-devel@lists.freedesktop.org, jacek.anaszewski@gmail.com, pavel@ucw.cz, robh+dt@kernel.org, mark.rutland@arm.com, linux-leds@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, Andy Gross , linux-arm-msm@vger.kernel.org, linux-fbdev@vger.kernel.org, phone-devel@vger.kernel.org Subject: Re: [PATCH V2 2/2] backlight: qcom-wled: Correct the sync_toggle sequence In-Reply-To: <20210226172601.aknj2d4hghkkqjol@maple.lan> References: <1614341544-5306-1-git-send-email-kgunda@codeaurora.org> <1614341544-5306-3-git-send-email-kgunda@codeaurora.org> <20210226172601.aknj2d4hghkkqjol@maple.lan> Message-ID: <0cca377c2a7648c5f1606e38ba1b7d4d@codeaurora.org> X-Sender: kgunda@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org On 2021-02-26 22:56, Daniel Thompson wrote: > On Fri, Feb 26, 2021 at 05:42:24PM +0530, Kiran Gunda wrote: >> As per the current implementation, after FSC (Full Scale Current) >> and brightness update the sync bits are transitioned from 1 to 0. > > This still seems to incorrectly describe the current behaviour. > > Surely in most cases (i.e. every time except the first) the value of > the > sync bit is 0 when the function is called and we get both a 0 to 1 > and then a 1 to 0 transition. > > That is why I recommended set-then-clear terminology to describe the > current behaviour. It is concise and correct. > > > Daniel. > > > Okay. Actually I have mentioned the "clear-and-set" in explaining the fix. Let me modify the same terminology in explaining the problem case also. >> But, the FSC and brightness sync takes place during a 0 to 1 >> transition of the sync bits. So the hardware team recommends a >> clear-then-set approach in order to guarantee such a transition >> regardless of the previous register state. >> >> Signed-off-by: Kiran Gunda >> --- >> drivers/video/backlight/qcom-wled.c | 12 ++++++------ >> 1 file changed, 6 insertions(+), 6 deletions(-) >> >> diff --git a/drivers/video/backlight/qcom-wled.c >> b/drivers/video/backlight/qcom-wled.c >> index aef52b9..19f83ac 100644 >> --- a/drivers/video/backlight/qcom-wled.c >> +++ b/drivers/video/backlight/qcom-wled.c >> @@ -337,13 +337,13 @@ static int wled3_sync_toggle(struct wled *wled) >> >> rc = regmap_update_bits(wled->regmap, >> wled->ctrl_addr + WLED3_SINK_REG_SYNC, >> - mask, mask); >> + mask, WLED3_SINK_REG_SYNC_CLEAR); >> if (rc < 0) >> return rc; >> >> rc = regmap_update_bits(wled->regmap, >> wled->ctrl_addr + WLED3_SINK_REG_SYNC, >> - mask, WLED3_SINK_REG_SYNC_CLEAR); >> + mask, mask); >> >> return rc; >> } >> @@ -353,17 +353,17 @@ static int wled5_mod_sync_toggle(struct wled >> *wled) >> int rc; >> u8 val; >> >> - val = (wled->cfg.mod_sel == MOD_A) ? WLED5_SINK_REG_SYNC_MOD_A_BIT : >> - WLED5_SINK_REG_SYNC_MOD_B_BIT; >> rc = regmap_update_bits(wled->regmap, >> wled->sink_addr + WLED5_SINK_REG_MOD_SYNC_BIT, >> - WLED5_SINK_REG_SYNC_MASK, val); >> + WLED5_SINK_REG_SYNC_MASK, 0); >> if (rc < 0) >> return rc; >> >> + val = (wled->cfg.mod_sel == MOD_A) ? WLED5_SINK_REG_SYNC_MOD_A_BIT : >> + WLED5_SINK_REG_SYNC_MOD_B_BIT; >> return regmap_update_bits(wled->regmap, >> wled->sink_addr + WLED5_SINK_REG_MOD_SYNC_BIT, >> - WLED5_SINK_REG_SYNC_MASK, 0); >> + WLED5_SINK_REG_SYNC_MASK, val); >> } >> >> static int wled_ovp_fault_status(struct wled *wled, bool *fault_set) >> -- >> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora >> Forum, >> a Linux Foundation Collaborative Project >>