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t=1790683974; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=YIcJiMvSHwtCZnraYE7wCGLbPbIrNhutTgj56ANQtZQ=; b=AbXarkRI7d1uL5pGMTN/5au3nH00ZVes00ljfBw59yD7Qjr/1kIgkQsn4S3NDsbaTe3pvc 86+w92S4SwvByTCCrF4jbvLZiJfCP0dDiAhaEY/liQAN7VygMySW4NTP2w1kHORudDHOGV yCikEM0v8ls11Lr+17vkgfM8U2yy1RY= Message-ID: <49805bcc-2456-4f7d-a08a-3ccb7223ea50@ixit.cz> Date: Tue, 29 Sep 2026 14:12:53 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 06/11] drm/panel: s6e3ha8: Correct the polarity logic within To: Krzysztof Kozlowski , Neil Armstrong Cc: Dzmitry Sankouski , Jessica Zhang , David Airlie , Simona Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Bjorn Andersson , Konrad Dybcio , Abel Vesa , Petr Vorel , dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, phone-devel@vger.kernel.org References: <20260924-crosshatch-panel-v2-0-08d5c7bf72fc@ixit.cz> <20260924-crosshatch-panel-v2-6-08d5c7bf72fc@ixit.cz> <20260929-dramatic-ocelot-of-support-2aa377@quoll> <739ce9f4-8bdb-4bc4-9cc1-9a1a7eba80ce@ixit.cz> Content-Language: en-US, cs-CZ From: David Heidelberg Autocrypt: addr=david@ixit.cz; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam: Yes On 29/09/2026 12:36, Krzysztof Kozlowski wrote: > On 29/09/2026 11:59, David Heidelberg wrote: >> On 29/09/2026 11:51, Krzysztof Kozlowski wrote: >>> On 29/09/2026 11:41, David Heidelberg wrote: >>>> On 29/09/2026 09:45, Krzysztof Kozlowski wrote: >>>>> On Thu, Sep 24, 2026 at 04:01:34PM +0200, David Heidelberg wrote: >>>>>> The reset was introduced with wrong polarity. Correct for the future >>>>>> compatibles and keep current with reverted logic. >>>>>> >>>>>> Old DTs keep GPIO_ACTIVE_HIGH and are fixed up via >>>>>> gpiod_toggle_active_low() on the deprecated compatible. >>>>>> >>>>>> Assisted-by: LLM >>>>>> Reviewed-by: Neil Armstrong >>>>>> Signed-off-by: David Heidelberg >>>>>> --- >>>>>> drivers/gpu/drm/panel/panel-samsung-s6e3ha8.c | 23 +++++++++++++++++++---- >>>>>> 1 file changed, 19 insertions(+), 4 deletions(-) >>>>>> >>>>>> diff --git a/drivers/gpu/drm/panel/panel-samsung-s6e3ha8.c b/drivers/gpu/drm/panel/panel-samsung-s6e3ha8.c >>>>>> index 5e1e997b83b36..99290913de69a 100644 >>>>>> --- a/drivers/gpu/drm/panel/panel-samsung-s6e3ha8.c >>>>>> +++ b/drivers/gpu/drm/panel/panel-samsung-s6e3ha8.c >>>>>> @@ -20,16 +20,17 @@ >>>>>> #include "panel-samsung-dsi.h" >>>>>> >>>>>> struct s6e3ha8_desc { >>>>>> const struct drm_panel_funcs *funcs; >>>>>> const struct drm_display_mode *mode; >>>>>> unsigned long mode_flags; >>>>>> const struct regulator_bulk_data *supplies; >>>>>> unsigned int num_supplies; >>>>>> + bool broken_reset_polarity; >>>>>> }; >>>>>> >>>>>> struct s6e3ha8 { >>>>>> struct drm_panel panel; >>>>>> struct mipi_dsi_device *dsi; >>>>>> const struct s6e3ha8_desc *desc; >>>>>> struct drm_dsc_config dsc; >>>>>> struct gpio_desc *reset_gpio; >>>>>> @@ -62,22 +63,22 @@ static int s6e3ha8_unprepare(struct drm_panel *panel) >>>>>> { >>>>>> struct s6e3ha8 *priv = to_s6e3ha8(panel); >>>>>> >>>>>> return regulator_bulk_disable(priv->desc->num_supplies, priv->supplies); >>>>>> } >>>>>> >>>>>> static void s6e3ha8_amb577px01_wqhd_reset(struct s6e3ha8 *priv) >>>>>> { >>>>>> - gpiod_set_value_cansleep(priv->reset_gpio, 1); >>>>>> - usleep_range(5000, 6000); >>>>>> gpiod_set_value_cansleep(priv->reset_gpio, 0); >>>>>> usleep_range(5000, 6000); >>>>>> gpiod_set_value_cansleep(priv->reset_gpio, 1); >>>>>> usleep_range(5000, 6000); >>>>>> + gpiod_set_value_cansleep(priv->reset_gpio, 0); >>>>> >>>>> This breaks all users and this usage of ABI was already released. >>>> >>>> See the gpiod_toggle_active_low() usage later in the patch which keep the logic >>>> for the original compatible as intended. >>>> >>> >>> OK, I went way too fast, that's correct part. But splitting fix is still >>> just confusing. Backporting to stable is a different thing than fixing >>> issues. >> >> Sure, I already droped the previous commit changing it for stable. >> >> Btw. looking at gpiod_toggle_active_low(), would it make sense to do a series >> correcting panel reset logic? I see many panels keep "reset asserted" in the >> driver (but ofc not in the reality). > > > To my knowledge it is impossible task to do, without breaking something. I would do the partial change (only driver, not full DT). So we end up with drivers having the correct logic with extra 2-line DT quirk using gpiod_toggle_active_low() for given compatible. This could solve people implementing new panel on top of existing DDIC and allow them to use the right polarity for new compatible. David > Either you break users of ABI (so the DTS) or break existing users of > DTS. One could try to avoid both by using your approach here with > compatibles having fallback. But then what polarity actually would be in > such DTS node? If you know your users, like for some SoC components, you > could argue that none of then will be affected. But both the driver and > DTS here can be used externally. > > Best regards, > Krzysztof