From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from ixit.cz (ixit.cz [84.42.129.46]) (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 40F08415B6E; Mon, 14 Sep 2026 21:05:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=84.42.129.46 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789419902; cv=none; b=NGvsVRZDy49kUV6arKtJIXHCjOyZBVP2I0jstf+xf3G6Wq2+4EAys6HNcHS5uVV6n9UD8Kup3wblPhqlVHOzv605sy/g4/+cSsqEIWwqqdK3bGVags/UnHuqF+qkdMsEwOEzXAEyEqjQfqDWKFaPTfIHB701YTrGTyU1PK9F+/E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789419902; c=relaxed/simple; bh=ihzL+l2KI7XVSNewbML1ta9wvrsrafmVC9sc5kiBTMQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=oNQk+gCK2XkjmjQc4C5XkEYP9UVBgRsmxQ2GtdlahpolH+EtJveYYjPNTcR1EXHY//drQmQwh9Bz+wWP4aVMZT5gBeQzg8vaCrI59VZa2TG5gEUQqoO0Un5rr1HJVj3s6qfP3pYvYz3cKbSFN84r/y4Dn7oRQ0+RzByUh4ZFPqY= ARC-Authentication-Results:i=1; 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t=1789419897; 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=Ucz9EKe46ScLEmo/7CYnL5FFLCA5CmnkIuajSNz4/sM=; b=s8kSuDxhBCJOBKfjaXao3nCX/kanfcxEbJQGfERqu72Y9OPDhA7T1om6S56G9uzZNjYufm 3uH3/Ldk+1uUYJLbPm8bwI/LbZFzyrswqY+2Lw20PrH7cQPp/q6AfJMf9Gm7K/g+Jf6Pwp EKyUFr+/wb27p9Prc8yTKYjUaanUOQo= Message-ID: Date: Mon, 14 Sep 2026 23:04:56 +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 1/2] drm/panel: lg-sw43408: do not assert reset across unprepare To: Sumit Semwal , Casey Connolly , Neil Armstrong , Jessica Zhang , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Dmitry Baryshkov , Marijn Suijten , Vinod Koul Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, phone-devel@vger.kernel.org References: <20260810-fix-blueline-panel-v2-0-9344dfdbc3f9@ixit.cz> <20260810-fix-blueline-panel-v2-1-9344dfdbc3f9@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 On 10/08/2026 11:55, David Heidelberg via B4 Relay wrote: > From: David Heidelberg > > Asserting the reset GPIO in unprepare() and leaving it asserted puts > the DDIC into a state it never recovers from: after the following > prepare() the panel answers all DCS commands, reports display-on with > clean self-diagnostics, and its configuration registers read back > identical to a working panel, but it never lights up again. > > On the Pixel 3, vddi is shared with the touchscreen controller and > remains powered while the panel is off, so with this driver the DDIC > sits in reset with its logic rail up for the whole blank period - a > state the vendor stack never creates: the vendor firmware only toggles > reset as part of a full power-on sequence, and the vendor OS never > power-cycles the panel at all (LP mode is used instead). > > Leave reset alone in unprepare(); prepare() performs the regular reset > sequence anyway. > > Without this, the Pixel 3 display never comes back after the first > blank/unblank cycle. > > Since there isn't any other panel or device using this DDIC, this > approach seems resoanble to address the issue. > > Fixes: 069a6c0e94f9 ("drm: panel: Add LG sw43408 panel driver") > Reviewed-by: Neil Armstrong > Signed-off-by: David Heidelberg > --- > drivers/gpu/drm/panel/panel-lg-sw43408.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > Good news is, that this patch really doesn't make panel power-off fatal for the phone, but recent testing got me into state where I observed: 10 hours, display on, phone operating normally. display on (various time), display off, display on OK, but sometimes display on, display off (for longer time), after pressing power button (to wake up) the phone reboot into bootloader. Nothing printed into dmesg (I'll try enable drm-debug, but not having high hopes. So far, this is still heavy improvement comparing to instant crash, but not the perfect solution either. David > diff --git a/drivers/gpu/drm/panel/panel-lg-sw43408.c b/drivers/gpu/drm/panel/panel-lg-sw43408.c > index 293826c5006b9..0bf8e08f10b9c 100644 > --- a/drivers/gpu/drm/panel/panel-lg-sw43408.c > +++ b/drivers/gpu/drm/panel/panel-lg-sw43408.c > @@ -50,18 +50,24 @@ static int sw43408_unprepare(struct drm_panel *panel) > int ret; > > mipi_dsi_dcs_set_display_off_multi(&ctx); > > mipi_dsi_dcs_enter_sleep_mode_multi(&ctx); > > mipi_dsi_msleep(&ctx, 100); > > - gpiod_set_value(sw43408->reset_gpio, 1); > - > + /* > + * Keep reset deasserted: vddi may stay powered (it is shared with > + * the touchscreen on Pixel 3) and holding the DDIC in reset while > + * its logic rail is up puts it into a state that no init sequence > + * recovers from - the panel keeps answering DCS commands and > + * reports display-on, but never lights up again. The vendor stack > + * only ever toggles reset as part of a powered-up init sequence. > + */ > ret = regulator_bulk_disable(ARRAY_SIZE(sw43408_supplies), sw43408->supplies); > > return ret ? : ctx.accum_err; > } > > static int sw43408_program(struct drm_panel *panel) > { > struct sw43408_panel *sw43408 = to_panel_info(panel); >