From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6404BC433DB for ; Sat, 6 Feb 2021 00:00:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 24DF16500F for ; Sat, 6 Feb 2021 00:00:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230402AbhBEX7v (ORCPT ); Fri, 5 Feb 2021 18:59:51 -0500 Received: from vps0.lunn.ch ([185.16.172.187]:50406 "EHLO vps0.lunn.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231621AbhBENyY (ORCPT ); Fri, 5 Feb 2021 08:54:24 -0500 Received: from andrew by vps0.lunn.ch with local (Exim 4.94) (envelope-from ) id 1l81Xt-004Nc1-KH; Fri, 05 Feb 2021 14:53:13 +0100 Date: Fri, 5 Feb 2021 14:53:13 +0100 From: Andrew Lunn To: Takashi Iwai Cc: Hans Verkuil , Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, "Matwey V. Kornilov" , Robert Foss Subject: Re: [PATCH] media: pwc: Fix the URB buffer allocation Message-ID: References: <20210121202855.17400-1-tiwai@suse.de> <7afd0612-de36-60b1-6650-6f8de24a7145@xs4all.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 05, 2021 at 02:42:23PM +0100, Takashi Iwai wrote: > On Fri, 05 Feb 2021 14:13:02 +0100, > Andrew Lunn wrote: > > > > Hi Takashi > > > > > Indeed, looks so. In most cases, this doesn't matter since both point > > > to the same device object. In some cases like xhci-plat HCD, they > > > differ. And sysdev might be a better choice from the consistency > > > POV. > > > > > > But this brought an interesting question, too. eg. USB chipidea > > > HCD uses platform devices for both controller and sysdev, and I > > > couldn't find any DMA mask setup. So, no matter what to use, the uwc > > > driver would be broken on this... Maybe it's just not covered. > > > > Did you do a git bisect to see what actually broke it? "1161db6776bd: > > media: usb: pwc: Don't use coherent DMA buffers for ISO transfer" > > introduced the code, not the regression. If we understand the > > regression, that might give us the answer about chipidea. > > It's the recent DMA core change, the commit f959dcd6ddfd ("dma-direct: > Fix potential NULL pointer dereference"). But basically it's a right > fix, and the driver hitting this "regression" has been already broken > but casually worked without setting a proper DMA mask. So for the chipidea, it also just 'casually worked'. But now it probably does not. But that is a separate chipidea issue. None of my ARM systems use the chipidea IP core, so i cannot test anything. Andrew