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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 99D89C4321E for ; Fri, 2 Dec 2022 16:10:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233660AbiLBQKP (ORCPT ); Fri, 2 Dec 2022 11:10:15 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49460 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232315AbiLBQKN (ORCPT ); Fri, 2 Dec 2022 11:10:13 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ED92AACA5C for ; Fri, 2 Dec 2022 08:10:12 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 9E2FDB821E6 for ; Fri, 2 Dec 2022 16:10:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BA2FCC433D6; Fri, 2 Dec 2022 16:10:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1669997410; bh=pY7GxkPoYDDAU3TZ6koKkSzCTbxeST3lXEvYEd5lxqo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=2iz181rBBRvc23kA2L1olkpMyRP2SNz+tVYU+5vXH9vDD1q5YMzFYv+wAlPxdaqfM umrK2KdRvxPxb9mZf65PwgfIG1gkRsud0Y93/MeYQA1ZaZ7aIOWlUEyxCCEY1+pAk6 dEecQvwg8Qc1zo9nKRfVkna20J+Obh+1wURMz5Qk= Date: Fri, 2 Dec 2022 17:10:07 +0100 From: Greg KH To: Thorsten Leemhuis Cc: Will Deacon , Amit Pundir , Catalin Marinas , Sibi Sankar , Manivannan Sadhasivam , Robin Murphy , andersson@kernel.org, sumit.semwal@linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, hch@lst.de Subject: Re: [PATCH] Revert "arm64: dma: Drop cache invalidation from arch_dma_prep_coherent()" Message-ID: References: <20221118123349.GC3697@willie-the-truck> <20221121064224.GB11945@thinkpad> <018517b8-0ae0-54f5-f342-dcf1b3330a13@quicinc.com> <6d637906-e1d5-c481-a73d-2b2b845e223b@leemhuis.info> <20221202100357.GB29396@willie-the-truck> <92a148a3-a8ac-4065-123c-99b72ac3ebeb@leemhuis.info> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <92a148a3-a8ac-4065-123c-99b72ac3ebeb@leemhuis.info> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 02, 2022 at 11:34:30AM +0100, Thorsten Leemhuis wrote: > On 02.12.22 11:03, Will Deacon wrote: > > On Fri, Dec 02, 2022 at 09:54:05AM +0100, Thorsten Leemhuis wrote: > >> On 02.12.22 09:26, Amit Pundir wrote: > >>> On Thu, 1 Dec 2022 at 23:15, Catalin Marinas wrote: > >>>> > >>>> On Thu, Dec 01, 2022 at 10:29:39AM +0100, Thorsten Leemhuis wrote: > >>>>> Has any progress been made to fix this regression? It afaics is not a > >>>>> release critical issue, but well, it still would be nice to get this > >>>>> fixed before 6.1 is released. > >>>> > >>>> The only (nearly) risk-free "fix" for 6.1 would be to revert the commit > >>>> that exposed the driver bug. It doesn't fix the actual bug, it only > >>>> makes it less likely to happen. > >>>> > >>>> I like the original commit removing the cache invalidation as it shows > >>>> drivers not behaving properly > >> > >> Yeah, I understand that, but I guess it's my job to ask at this point: > >> "is continuing to live with the old behavior for one or two more cycles" > >> that much of a problem"? > > > > That wouldn't be a problem. The problem is that I haven't see any efforts > > from the Qualcomm side to actually fix the drivers [...] > > Thx for sharing the details. I can fully understand your pain. But well, > in the end it looks to me like this commit it intentionally breaking > something that used to work -- which to my understanding of the "no > regression rule" is not okay, even if things only worked by chance and > not flawless. "no regressions" for userspace code, this is broken, out-of-tree driver code, right? I do not think any in-kernel drivers have this issue today from what I can tell, but if I am wrong here, please let me know. We don't keep stable apis, or even functionality, for out-of-tree kernel code as that would be impossible for us to do for obvious reasons. thanks, greg kh