From patchwork Sat Aug 24 00:10:39 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= X-Patchwork-Id: 1152524 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=none (p=none dis=none) header.from=kleine-koenig.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 46Fdw35y9Wz9sBF for ; Sat, 24 Aug 2019 10:10:59 +1000 (AEST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726279AbfHXAK7 (ORCPT ); Fri, 23 Aug 2019 20:10:59 -0400 Received: from antares.kleine-koenig.org ([94.130.110.236]:56636 "EHLO antares.kleine-koenig.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725782AbfHXAK7 (ORCPT ); Fri, 23 Aug 2019 20:10:59 -0400 Received: by antares.kleine-koenig.org (Postfix, from userid 1000) id 1239877D4BA; Sat, 24 Aug 2019 02:10:58 +0200 (CEST) From: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= To: Claudiu Beznea , Thierry Reding Cc: Nicolas Ferre , Alexandre Belloni , Ludovic Desroches , linux-arm-kernel@lists.infradead.org, linux-pwm@vger.kernel.org Subject: [PATCH v2 4/6] pwm: atmel: document known weaknesses of both hardware and software Date: Sat, 24 Aug 2019 02:10:39 +0200 Message-Id: <20190824001041.11007-5-uwe@kleine-koenig.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190824001041.11007-1-uwe@kleine-koenig.org> References: <20190824001041.11007-1-uwe@kleine-koenig.org> MIME-Version: 1.0 Sender: linux-pwm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pwm@vger.kernel.org This documents the my findings while reading through the driver and the reference manual. Signed-off-by: Uwe Kleine-König --- Changes since (implicit) v1 sent with Message-Id: 20190816093748.11769-1-uwe@kleine-koenig.org: - Add some prosa to commit log drivers/pwm/pwm-atmel.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c index 3786ab9db5cf..89f3a62f7541 100644 --- a/drivers/pwm/pwm-atmel.c +++ b/drivers/pwm/pwm-atmel.c @@ -7,6 +7,16 @@ * * Links to reference manuals for the supported PWM chips can be found in * Documentation/arm/microchip.rst. + * + * Limitations: + * - Periods start with the inactive level. + * - Hardware has to be stopped in general to update settings. + * + * Software bugs/possible improvements: + * - When atmel_pwm_apply() is called with state->enabled=false a change in + * state->polarity isn't honored. + * - Instead of sleeping to wait for a completed period, the interrupt + * functionality could be used. */ #include