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: 11112551 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 634A51395 for ; Sat, 24 Aug 2019 00:12:12 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3976E20850 for ; Sat, 24 Aug 2019 00:12:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Tzw7N2dk" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3976E20850 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kleine-koenig.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=mbaxhg8/TmtLEuvCoQkIrrJxCx8xYhgH1viX1StuFWc=; b=Tzw7N2dk057e3i mU4pbYNASwG45Mi3DEtFvN7b0aba7F47CRt9wMqYlr51Wurcek7roGQjIjAzk3f26DSSUg9rNjOBQ FwQTYSl9FcqQpeZ/58M7jzn5MCHhOA0xehf5Kq88b0nIAwS/QaIi6TyjfelQws9/qa6vrp44NJYMq UvmJ7aF3z1cbhE6uBmdkR5RoCS4fiTu6MZtOK70sugDCKMOYF+iZrdLgiWAz1sXNQPsFXsNR7HApv i2pnRWe45OR0cDrvDiI2ocjgqScoQ5iTKMDemwxZSIFotiF03F+6QEnVmzF8/iulwDnbMl5z0Rjka Hby0HiX+HZSPiXcWoLWA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i1Jf9-00030g-MP; Sat, 24 Aug 2019 00:12:11 +0000 Received: from antares.kleine-koenig.org ([94.130.110.236]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1i1JeT-00026t-IO for linux-arm-kernel@lists.infradead.org; Sat, 24 Aug 2019 00:11:31 +0000 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 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 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190823_171129_774962_2BFA802C X-CRM114-Status: UNSURE ( 9.53 ) X-CRM114-Notice: Please train this message. X-Spam-Score: -0.0 (/) X-Spam-Report: SpamAssassin version 3.4.2 on bombadil.infradead.org summary: Content analysis details: (-0.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [94.130.110.236 listed in list.dnswl.org] -0.0 SPF_HELO_PASS SPF: HELO matches SPF record -0.0 SPF_PASS SPF: sender matches SPF record X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-pwm@vger.kernel.org, Alexandre Belloni , Ludovic Desroches , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.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