From patchwork Sat May 25 18:11:33 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Martin Blumenstingl X-Patchwork-Id: 1105387 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-pwm-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=googlemail.com Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=googlemail.com header.i=@googlemail.com header.b="YUJZFmlD"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 45BBCT4lHHz9s3Z for ; Sun, 26 May 2019 04:12:05 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727382AbfEYSME (ORCPT ); Sat, 25 May 2019 14:12:04 -0400 Received: from mail-wm1-f68.google.com ([209.85.128.68]:36806 "EHLO mail-wm1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727606AbfEYSMC (ORCPT ); Sat, 25 May 2019 14:12:02 -0400 Received: by mail-wm1-f68.google.com with SMTP id v22so4816675wml.1; Sat, 25 May 2019 11:12:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=nIoMcTrrivGWjqKFRKrQpbhTg0DwU0FAQEhN7ghOLBc=; b=YUJZFmlDDS9sV9t0FwAaA3uob1RJ1IKO64k1hx0VeZz++jx4eM8XoCSEP1HQUW5YCT Yg6X8OMcyRuAess6huRflmv0SgTKddbbEXVnjxBnlrmS5zgBf8Thu4QSXkel6JrF4gH6 0Nh+RzfkXnEzfzWU7jlm6MI9ivRU911ji63yc4ZRaWY8W8NNaYsfPznlNTHwgwlJYYid YgWjrUYKMFuyG/odJ1p+d8OF7MrkrEenArWMUleMDXqjhnh9om7QZJr8agRXOjq1Ys/a pgBINls59AMYHNDXQ+tROISOkYdsCpFcSC9EKYw7kepQE4tjK/7VY8yu6O/Zm74+SovP uunw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=nIoMcTrrivGWjqKFRKrQpbhTg0DwU0FAQEhN7ghOLBc=; b=aDYYB2at/BSf5De0eZTwBq5TZ3LLf4UhMKo2ofeNzSXWrhsShFPXZgxhXJZaZsI3Xa 7wAH4h+ui2TVD9RfyFSfTkPjDhAu/VStGQGyqe2emEEVq2J/WomVTW/vnQLHtbsi8PEp utpiY8zJn/Xa4sAzeRaXhBoCTLHI7ivmh8mDBb1PU4NVezeqD1GogEKviW2K7YJZpmWI EiK1M+SGdy/4cOmBb2bWPZ4NZzm5pN4RG7sv62q8xk3h8YkN6TTdGnxLKIdzjq6OHW1T jTRe3HpkC09T4U4t8CU6gxoG/4jUL20Bghv3H5h4f1LM20caEE136C4op+3+/NQcJRiA U9PA== X-Gm-Message-State: APjAAAUGoAhUHoyoO2pwgJSN7ONR8E+Hn382gJX8nwJiUS8uTuQYS5mJ v39C96j1wgJX4Kous5mFoZE= X-Google-Smtp-Source: APXvYqyu3Be/yKPBPoTWAwazVEJwspi1jbLIzkDvL+i+B9Xl8I2P+UA0mJcEPB3BnlTthJdpmkyPcQ== X-Received: by 2002:a1c:a002:: with SMTP id j2mr20147153wme.131.1558807920083; Sat, 25 May 2019 11:12:00 -0700 (PDT) Received: from blackbox.darklights.net (p200300F133DDA4007CB8841254CD64FD.dip0.t-ipconnect.de. [2003:f1:33dd:a400:7cb8:8412:54cd:64fd]) by smtp.googlemail.com with ESMTPSA id o8sm12794540wra.4.2019.05.25.11.11.59 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 25 May 2019 11:11:59 -0700 (PDT) From: Martin Blumenstingl To: linux-amlogic@lists.infradead.org, linux-pwm@vger.kernel.org, thierry.reding@gmail.com, u.kleine-koenig@pengutronix.de Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Martin Blumenstingl , Neil Armstrong Subject: [PATCH 14/14] pwm: meson: add documentation to the driver Date: Sat, 25 May 2019 20:11:33 +0200 Message-Id: <20190525181133.4875-15-martin.blumenstingl@googlemail.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190525181133.4875-1-martin.blumenstingl@googlemail.com> References: <20190525181133.4875-1-martin.blumenstingl@googlemail.com> MIME-Version: 1.0 Sender: linux-pwm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org Add a link to the datasheet and a short summary how the hardware works. The goal is to make it easier for other developers to understand why the pwm-meson driver is implemented the way it is. Suggested-by: Uwe Kleine-König Co-authored-by: Neil Armstrong Signed-off-by: Martin Blumenstingl Reviewed-by: Neil Armstrong --- drivers/pwm/pwm-meson.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c index bb48ba85f756..6a978caba483 100644 --- a/drivers/pwm/pwm-meson.c +++ b/drivers/pwm/pwm-meson.c @@ -1,5 +1,23 @@ // SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause /* + * PWM controller driver for Amlogic Meson SoCs. + * + * This PWM is only a set of Gates, Dividers and Counters: + * PWM output is achieved by calculating a clock that permits calculating + * two periods (low and high). The counter then has to be set to switch after + * N cycles for the first half period. + * The hardware has no "polarity" setting. This driver reverses the period + * cycles (the low length is inverted with the high length) for + * PWM_POLARITY_INVERSED. This means that .get_state cannot read the polarity + * from the hardware. + * Setting the duty cycle will disable and re-enable the PWM output. + * Disabling the PWM stops the output immediately (without waiting for the + * current period to complete first). + * + * The public S922X datasheet contains some documentation for this PWM + * controller starting on page 1084: + * https://dl.khadas.com/Hardware/VIM2/Datasheet/S912_Datasheet_V0.220170314publicversion-Wesion.pdf + * * Copyright (c) 2016 BayLibre, SAS. * Author: Neil Armstrong * Copyright (C) 2014 Amlogic, Inc.