From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=178.238.236.174 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793002246; b=qI7ZVcj2GT/anakb867m3raNskPdKTLiyeZudXsb5fK2BE17wvM3rb5jkFaL50hEsHxg 5ofBokoZgNTs7EwK0sGcQ30FgvaQLCDqjemX4Qwiit9c3tW9GjpKTu6EM++19QfUOPzX2 sHxDld7Kbsdt//TMTDnPVovTKTYi0ar+/1CskSxzNVwKLW+j4nWTpMA3o6zKk6k+NAlou o5LkTVWtJQmtPhwEbhLGN7cak05oHTzPqVsd1fDlOtR5G5D6+Wa179YVekm6W/HVHIofa 1u8zW3rG7rAzBalRYktSD3AGZr3OYN2/dMr6b1hNCFeCq0SGuNt/CbxPYPEfl23tC2A== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793002246; h=DMARC-Filter:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: In-Reply-To:References:X-Mailer:MIME-Version:Content-Type: Content-Transfer-Encoding; bh=FT2R+3LBW1RgNSBu29PCS8eirV9Pz7HjQL+1gPg5bno=; b=2Q5/yO4NUGcW+88oB8hNT/9z0NLjaX+qvkq4gL97W5Ia6M+4R2cMxnA2yer8icuyi5/8 KRr8Nyvvvloxqq4RvFKHxP/3RivlVABFqkPl2NurOUNSdraGBRYxyWLnqiozs2mTIKNlG Jn4SUqr6iNBP5ttjLBnjhyjWwEekuA9bcXH1pBDHzeRaOSpOVIfkjdWlWQYZlrda+f4uw 0d3/c2DXkQFoRfUS9vML7qN8wdvRtnq5BDPrTqBnO1Zun/KmATCn/mgFVGPC97OWVruGh tRhK1TjWGGBgo4ZZ1z72dxDtx195r1tmVQKj87XCvo9/jyogbeZ8CphqKG9JSsSkSyg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=kemnade.info; spf=pass smtp.mailfrom=kemnade.info; dkim=pass header.d=kemnade.info header.i=@kemnade.info header.a=rsa-sha256 header.s=20220719 header.b="sy9Pf/tb"; arc=none smtp.remote-ip=178.238.236.174 Received: from mail.andi.de1.cc (mail.andi.de1.cc [178.238.236.174]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 83D78606A31A for ; Mon, 26 Oct 2026 08:10:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 83D78606A31A Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=kemnade.info Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kemnade.info Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kemnade.info header.i=@kemnade.info header.a=rsa-sha256 header.s=20220719 header.b=sy9Pf/tb DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=kemnade.info; s=20220719; h=References:In-Reply-To:Subject:Cc:To:From: Reply-To:Content-ID:Content-Description; bh=FT2R+3LBW1RgNSBu29PCS8eirV9Pz7HjQL+1gPg5bno=; t=1793002246; x=1794211846; b=sy9Pf/tbEYmKkvRpsy8UdaS35GQvhJrVzX3l7+IagA9wEFjXYK0OY/eDrFynnAzz/UNC9o3WmrL 2ctmEtYco/At3EwK2DlM9N0aJz/6/ETVANnhSSD4O8f2MKuDvSZQE/Ztttl8PGUyLJHoEdvVtxNOF w22WQIAbY+FgsHpE6iIRkLGxQ/YTdiK0uymWTOVa/5gR2hdMoBIc0f/AKRbm5Lbb992qPfaCTAij9 aPAvxZ9VY1cHe1tvXU8N7vBPTLhaSe4AAS7Sdb6gzqqzTX8xEg70RfNgfv5VHmq5lw3dcd5vLM2d2 hpKVbhIeafOdK1m4FgMKC/mm2YI3+y0WJ3JQ==; Date: Mon, 26 Oct 2026 09:10:42 +0100 From: Andreas Kemnade To: Pablo Mazzini Cc: Mark Brown , Liam Girdwood , Alistair Francis , linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/7] regulator: sy7636a: wait for power good, then switch VCOM_EN Message-ID: <20261026091042.5376dd7d@kemnade.info> In-Reply-To: <20261026003918.155321-5-pmazzini@gmail.com> References: <20261026003918.155321-1-pmazzini@gmail.com> <20261026003918.155321-5-pmazzini@gmail.com> X-Mailer: Claws Mail 4.3.1 (GTK 3.24.49; aarch64-unknown-linux-gnu) X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 26 Oct 2026 00:39:15 +0000 Pablo Mazzini wrote: > Wait for power good on enable, as the TPS65185 and FP9931 drivers do. > which is a good idea that the consumers can relay on the regulators being useable when enabled. > The VCOM_EN line was requested but held low. When it is wired, let it > switch VCOM after power good. > What is the reason for this change? VCOM gets enabled this way, too. I added this line just for having the hardware completely documented. A possible scenario where I could imagine this line being useful: Calibration of required VCOM voltage, You would turn on everything else, do a mode 0 refresh on the EPD and measure some kickback voltage on the otherwise inactive VCOM line and have your calculated value for that regulator. To be useful, several things are needed: - SY7636a driver needs to model vcom as a separate regulator turning on a vposneg regulator. The TPS65185 driver defines a vposneg regulator. - ADC input is needed. The TPS65185 provides (not implemented in the driver yet) such measurement. Of course that can come from another chip. - Some (probably userspace logic) to control all of this. Regards, Andreas