From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 95365175A92; Fri, 26 Jun 2026 07:38:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782459537; cv=none; b=kmK7+3D/Wj5dTkxOJvqUNy4Kx7qhPYZ3NXggaTrf96rdDaKfuG9jEWIs9dAoO1FvKPoXJnalYVVmiGLxI+XnFL8BsRjyUScWpBXqVOoBwGn3ARtyCzwUnuuOCuvHJSZa2gTgk/GoLsQUtXESopsTjEy5SFrmjiOtFomkBaXPbrg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782459537; c=relaxed/simple; bh=Hyf3fJLZ3zUzV8C+aO71cNUV+rF6iuxLBesXm3Ad0pI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=f1z2bdiK6q7VtjG9q5F81uW5nczS1PzSKotZexAkzubbwZxiNVgK6vPHf3ThlUYOQGjiRlR9r9NlFNzPLxRgx5HDrAQ4JTw2gKJPohXGafaFNLiYQJKUWXpYjUXhEs+M4QmUuQGMQYofDpG6zoX5DIKE65cjJXVxwOmA3yzSKB4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BO2P4jk3; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BO2P4jk3" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 21C971F00A3A; Fri, 26 Jun 2026 07:38:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782459536; bh=ic8Bm5KdmIIXc6QloY21tIYgrTVRgIkjPmPTeOkkreU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=BO2P4jk3NTslrrLva3ZcZkVVj/ASsV0FGfySjnCevyCXdsq9TYlWipPzN7PCgeZD0 1qbelKqNv5rKTF+IqhR6QMzo+h5yhsRBfRRuuvuhOKw66q69PHCAmuqsMsyYy1GJ6E Ic1M+3yfpwwHRAkHy400wXTDxfd0SkpetfBQF6kPGiTSbdBnPboCjkuXsChySVPeDz QBbhAaOWDaV/WlAmvgSllpdR/LjqlfbLFxpvsH9GAGX5VqnnhDY/K0EFUzcVT60KiY 4iMYPUswndSLLOjeGDz19LMU2IYt1Ab4S6mZG3fDhA3Rh3v9ZGMeVTTkwht47jaKuB wP+qYm0GKb95Q== Message-ID: Date: Fri, 26 Jun 2026 09:38:48 +0200 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 2/2] drm/bridge: Add Lontium LT9611C(EX/UXD) MIPI DSI to HDMI driver To: Sunyun Yang Cc: robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, andrzej.hajda@intel.com, neil.armstrong@linaro.org, dmitry.baryshkov@oss.qualcomm.com, maarten.lankhorst@linux.intel.com, rfoss@kernel.org, mripard@kernel.org, Laurent.pinchart@ideasonboard.com, tzimmermann@suse.de, jonas@kwiboo.se, jernej.skrabec@gmail.com, devicetree@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, xmzhu@lontium.corp-partner.google.com, xmzhu@lontium.com, rlyu@lontium.com, xbpeng@lontium.com References: <20260508134009.4582-1-syyang@lontium.com> <20260508134009.4582-3-syyang@lontium.com> <3188f63f-5358-48d7-b934-af20a8f95c6f@kernel.org> <6371d1d8-cdfb-40fa-84c7-ba3ec4e2ac00@kernel.org> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 26/06/2026 04:15, Sunyun Yang wrote: > Krzysztof Kozlowski 于2026年6月25日周四 21:51写道： >> >> On 25/06/2026 15:40, Sunyun Yang wrote: >>> Sunyun Yang 于2026年6月25日周四 21:26写道： >>>> >>>> Krzysztof Kozlowski 于2026年6月25日周四 21:17写道： >>>>> >>>>> On 25/06/2026 15:14, Sunyun Yang wrote: >>>>>> Krzysztof Kozlowski 于2026年6月25日周四 20:54写道： >>>>>>> >>>>>>> On 08/05/2026 15:40, syyang@lontium.com wrote: >>>>>>>> + >>>>>>>> +static void lt9611c_reset(struct lt9611c *lt9611c) >>>>>>>> +{ >>>>>>>> + gpiod_set_value_cansleep(lt9611c->reset_gpio, 1); >>>>>>>> + msleep(20); >>>>>>>> + >>>>>>>> + gpiod_set_value_cansleep(lt9611c->reset_gpio, 0); >>>>>>>> + msleep(20); >>>>>>>> + >>>>>>>> + gpiod_set_value_cansleep(lt9611c->reset_gpio, 1); >>>>>>> >>>>>>> This is just plain wrong. Why do you assert, then de-assert and then >>>>>>> finally assert AGAIN the reset leaving the device in powerdown stage? >>>>>>> >>>>>> I am using software to emulate the hardware RESET button on our EVB. >>>>>> When the hardware RESET button is pressed while our chip is running, >>>>>> the signal level changes from HIGH to LOW and then back to HIGH. >>>>>> >>>>>> Of course, we can also use the following: >>>>>> static void lt9611c_reset(struct lt9611c *lt9611c) >>>>>> { >>>>>> gpiod_set_value_cansleep(lt9611c->reset_gpio, 0); >>>>>> msleep(50); >>>>>> gpiod_set_value_cansleep(lt9611c->reset_gpio, 1); >>>>>> msleep(20); >>>>>> } >>>>> >>>>> Makes no sense either and you just did not get the point and did not >>>>> answer my question. I asked WHY you leave asserted. Answer "we emulate" >>>>> is just plain wrong. >>>>> >>>>> So again please answer: >>>>> >>>>> Why do you leave device with reset asserted? >>>>> >>>> >>>> devicetree: reset-gpios = <&tlmm 128 GPIO_ACTIVE_HIGH>; >>>> >>>> GPIO_ACTIVE_HIGH: >>>> >>>> gpiod_set_value_cansleep(lt9611c->reset_gpio, 0); ------ reset pin >>>> is Low level : Clear the register configuration in the chip to stop >>>> the chip from working. >>>> >>>> gpiod_set_value_cansleep(lt9611c->reset_gpio, 1); ------ reset pin >>>> is high level: The chip resumes operation. >>>> >>>> >>> >>> Our purpose is: pull the level low to clear the register configuration >>> in the chip, and then pull it high to allow the MCU inside the chip to >>> re‑initialize the registers. >> >> >> And you do completely opposite... so that confirms your code is just wrong. >> > > The lontium-lt9611.yaml uses GPIO_ACTIVE_HIGH. I am just following the > rule of this device tree. If I modify the device tree to use > GPIO_ACTIVE_LOW, > and use the following code in my driver, then my driver would be correct. > However, would the existing kernel drivers lontium-lt9611uxc.c and > lontium-lt9611.c be affected? DT has nothing to do here. 1 is assert, 0 is de-assert. Your code does things opposite to any logic, because you finish function with reset asserted. Best regards, Krzysztof