From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753571AbaIHMji (ORCPT ); Mon, 8 Sep 2014 08:39:38 -0400 Received: from mailout3.w1.samsung.com ([210.118.77.13]:43694 "EHLO mailout3.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751781AbaIHMjg (ORCPT ); Mon, 8 Sep 2014 08:39:36 -0400 MIME-version: 1.0 Content-type: text/plain; charset=UTF-8 X-AuditID: cbfec7f4-b7f156d0000063c7-52-540da383676e Content-transfer-encoding: 8BIT Message-id: <1410179970.4300.16.camel@AMDC1943> Subject: Re: [RFC PATCH] dma: pl330: add Power Management support From: Krzysztof Kozlowski To: Lars-Peter Clausen Cc: Dan Williams , Vinod Koul , Michal Simek , Dan Carpenter , dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org, Kyungmin Park , Marek Szyprowski , Bartlomiej Zolnierkiewicz Date: Mon, 08 Sep 2014 14:39:30 +0200 In-reply-to: <1410163907.4300.5.camel@AMDC1943> References: <1409929562-29583-1-git-send-email-k.kozlowski@samsung.com> <5409D585.1040302@metafoo.de> <1410163907.4300.5.camel@AMDC1943> X-Mailer: Evolution 3.10.4-0ubuntu2 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrHLMWRmVeSWpSXmKPExsVy+t/xy7rNi3lDDM4eN7fYOGM9q8Xrf9NZ LKZPvcBosXrqX1aLs01v2C2WTJ7PanF51xw2i7VH7rJbvHsZYfGybz+LA5fH4j0vmTyWvDnE 6vHx6S0Wj74tqxg9Pm+S89j7+TdLAFsUl01Kak5mWWqRvl0CV8b7+VfZCmbyV+w4tpe9gfEt dxcjB4eEgInE8abiLkZOIFNM4sK99WxdjFwcQgJLGSVmvV3CDpLgFRCU+DH5HgtIPbOAvMSR S9kgYWYBdYlJ8xYxQ9R/ZpT49vAVI0S9vsTxLWvZQGxhAUeJ1rUTmUBsNgFjic3Ll4DFRQQ0 JP6/mcQO0sws8JFJ4vbUd2BFLAKqEg19m1lBlnECDZrx1Q9iQRejxMbfb1kgjlaWaOx3m8Ao MAvJebMQzpuF5LwFjMyrGEVTS5MLipPScw31ihNzi0vz0vWS83M3MULi4MsOxsXHrA4xCnAw KvHwJlzlCRFiTSwrrsw9xCjBwawkwss0mTdEiDclsbIqtSg/vqg0J7X4ECMTB6dUAyNXkeU5 q9fV22PehzxaMPvx+k2Z20wDhbhecfJrZh5T1VxvsO5meifnj8rk8G83r88qtf+Y/eiaK9t/ e/uXZ//aBbSGRZVKLrZZpehUPJV146+1h7xP90u6RR2NkmA+pfSX33ph4dbp59QnZ2rMuG2T Mbmiwjv7XNKMbpMrQcpiUmnuM6a6CimxFGckGmoxFxUnAgDj4KZWYQIAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On pon, 2014-09-08 at 10:11 +0200, Krzysztof Kozlowski wrote: > On pią, 2014-09-05 at 17:23 +0200, Lars-Peter Clausen wrote: > > On 09/05/2014 05:06 PM, Krzysztof Kozlowski wrote: > > [...] > > > @@ -2168,11 +2199,23 @@ static void pl330_issue_pending(struct dma_chan *chan) > > > { > > > struct dma_pl330_chan *pch = to_pchan(chan); > > > unsigned long flags; > > > + bool power_up; > > > > > > spin_lock_irqsave(&pch->lock, flags); > > > + power_up = list_empty(&pch->work_list); > > > list_splice_tail_init(&pch->submitted_list, &pch->work_list); > > > spin_unlock_irqrestore(&pch->lock, flags); > > > > > > + if (power_up) { > > > + /* > > > + * Warn on nothing pending. This may break our pm_runtime > > > + * usage counter as it is updated on work_list emptiness > > > + * status. > > > + */ > > > + WARN_ON(list_empty(&pch->work_list)); > > > + pm_runtime_get_sync(pch->dmac->ddma.dev); > > > > Unfortunately this does not work. pm_runtime_get_sync() may sleep, where as > > the issue_pending callback needs to be able to run from contexts in which > > sleeping is not possible. > > Thank you for pointing this out. It seems I'll have to find another > solution because I really need to runtime suspend this driver... I found that idea was wrong in few more places. The most important is that the pl330 is an AMBA device. This means that runtime suspend/resume callbacks are already implemented (drivers/amba/bus.c) and they are called instead of my callbacks. That would be fine... except that these callbacks in amba/bus.c call clk_preare()/clk_unprepare() which is not safe for atomic context. This prohibits me from using pm_runtime_irq_safe() which could solve problem pointed by you. Best regards, Krzysztof > > Best regards, > Krzysztof > > > > > > + } > > > + > > > pl330_tasklet((unsigned long)pch); > > > } > > > > > [...]