From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (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 6093E466B0E; Fri, 21 Aug 2026 09:45:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787305548; cv=none; b=I/1GFD+Y49w9d6XK51pKGI4XTNzxuqyMyhqYOjc3z47eQHziPQthkBZ+nQjbDLoNU6pacZAPc0hHda8GNKIHoRBRWS23XbsQBEjo1qXgwh3VLVf15zUMsCvzMIF8+3/lNSj2WNPCbo6xKwCRTyWkN44bmN1ZFT55cYQh8dAOBmY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787305548; c=relaxed/simple; bh=FmuNeO/2gbwPF6v+5N6ElQDNIvtDrpPAysHLpirSETo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=NDpnFcZ8N2SeGXDESwX6BuTP8ONsH7rCkfjk+w5voDsgA0t5+wY8Dnjy3Vxh+9+4seXCY/pkcg7L9a+W1T7mKwNoKr4OX5Weke2XgUtkmpPnF4dnk1sA1xDWk0Zrip0aGBW+Il3mBxSCXbvx411EOP0w5cMa/A5FegfV27T7mBc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=YaZBLv9i; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="YaZBLv9i" Received: from [192.168.88.20] (91-158-153-178.elisa-laajakaista.fi [91.158.153.178]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 7CB571583; Fri, 21 Aug 2026 11:44:16 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1787305457; bh=FmuNeO/2gbwPF6v+5N6ElQDNIvtDrpPAysHLpirSETo=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=YaZBLv9i2dae2/vtK/G/v2hZGB8JWKHXHHHGnagU9uj1+Zzoo4uvcXplPjDxZhUqJ prTxvhTQzjibdmt5ORabvwEwZWf0/gMlPBoiXbbgw3bfG6L/ncNqCqUxoA03lgo8UX PitKIbxW+77BF9x2rEJx791E4YC4bjOjUWddFLyo= Message-ID: Date: Fri, 21 Aug 2026 12:45:35 +0300 Precedence: bulk X-Mailing-List: linux-omap@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6] drm/omap: dsi: avoid sending bta sync all the time in writes To: Andreas Kemnade Cc: Linux-OMAP , Marek Vasut , "H. Nikolaus Schaller" , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Tomi Valkeinen , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Sebastian Reichel , Laurent Pinchart , Tony Lindgren , Ivaylo Dimitrov References: <20260804-vm-upstr-v6-1-1bf3748b2fa3@kemnade.info> Content-Language: en-US From: Tomi Valkeinen In-Reply-To: <20260804-vm-upstr-v6-1-1bf3748b2fa3@kemnade.info> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi, On 04/08/2026 11:37, Andreas Kemnade wrote: > Some chips need configuration commands to be sent first, before they can > send data. TC358762 for example needs PPI_LPTXTIMECNT configured > and PPI_STARTPPI set to 1 to be able to transmit anything. To be able to > configure such chips, do not send bta sync during writes if no acks are > requested. Instead just wait for the packet to be sent to avoid FIFO > overflows. There might be more to do about acks, but there seem to be > virtually no users of that flag. > > This came to light when fiddling with the Epson Moverio BT-200 display > which consists of 2 TC358762 bridges with SPI funneled through > to the unknown display chip. With that patch the bridge can be accessed, > Reading back registers works, when the above-mentioned registers are set. > > In Command-Mode update, there was a nop sent, apparently the most > relevant part was the bta sync to actually force low power mode. > > Video mode panel at OMAP4 (BT-200) and video mode at OMAP5 was tested. > > Fixes: e70965386353e ("drm/omap: dsi: simplify write function") > Signed-off-by: Andreas Kemnade Thanks, picking up to drm-misc-next. Tomi