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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=ham 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 A6976C4338F for ; Wed, 28 Jul 2021 08:37:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8A36660F9D for ; Wed, 28 Jul 2021 08:37:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234655AbhG1Ihi convert rfc822-to-8bit (ORCPT ); Wed, 28 Jul 2021 04:37:38 -0400 Received: from relay8-d.mail.gandi.net ([217.70.183.201]:43759 "EHLO relay8-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230501AbhG1Ihf (ORCPT ); Wed, 28 Jul 2021 04:37:35 -0400 Received: (Authenticated sender: clement.leger@bootlin.com) by relay8-d.mail.gandi.net (Postfix) with ESMTPSA id 2BE601BF20E; Wed, 28 Jul 2021 08:37:33 +0000 (UTC) Date: Wed, 28 Jul 2021 10:37:32 +0200 From: =?UTF-8?B?Q2zDqW1lbnQgTMOpZ2Vy?= To: Vinod Koul Cc: Ludovic Desroches , Tudor Ambarus , Alexandre Belloni , linux-arm-kernel@lists.infradead.org, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] dmaengine: at_xdmac: use module_platform_driver Message-ID: <20210728103732.3befa390@fixe.home> In-Reply-To: References: <20210625090042.17085-1-clement.leger@bootlin.com> <20210728093831.27430737@fixe.home> Organization: Bootlin X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org Le Wed, 28 Jul 2021 13:53:48 +0530, Vinod Koul a écrit : > On 28-07-21, 09:38, Clément Léger wrote: > > Le Wed, 28 Jul 2021 12:26:50 +0530, > > Vinod Koul a écrit : > > > > > On 25-06-21, 11:00, Clément Léger wrote: > > > > The driver was previously probed with platform_driver_probe. > > > > This does not allow the driver to be probed again later if > > > > probe function returns -EPROBE_DEFER. This patch replace the > > > > use of platform_driver_probe with module_platform_driver which > > > > allows that. > > > > > > > > Signed-off-by: Clément Léger > > > > --- > > > > drivers/dma/at_xdmac.c | 6 +----- > > > > 1 file changed, 1 insertion(+), 5 deletions(-) > > > > > > > > diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c > > > > index 64a52bf4d737..109a4c0895f4 100644 > > > > --- a/drivers/dma/at_xdmac.c > > > > +++ b/drivers/dma/at_xdmac.c > > > > @@ -2238,11 +2238,7 @@ static struct platform_driver > > > > at_xdmac_driver = { } > > > > }; > > > > > > > > -static int __init at_xdmac_init(void) > > > > -{ > > > > - return platform_driver_probe(&at_xdmac_driver, > > > > at_xdmac_probe); -} > > > > -subsys_initcall(at_xdmac_init); > > > > +module_platform_driver(at_xdmac_driver); > > > > > > You are also changing the init call here, there is a reason why > > > dmaengine drivers are subsys_initcall.. have you tested this? > > > > > > > I understood that the subsys initcall was there to probe the DMA > > driver earlier than other drivers (at least I guess this was the > > reason). I > > That is correct > > > also tested it and can confirm you this works as expected on my > > platform (sama5d2_xplained and sama5d27_som1). > > > > In my configuration, the clocks are provided using SCMI and the SCMI > > driver probes them later than other drivers. > > Heh, clocks should get probed even earlier Yes, even clocksources might need them... But that's another story. > > > With the current subsys_initcall, platform_driver_probe calls > > __platform_driver_probe which will eventually calls platform_probe. > > This one will fails because SCMI clocks are not available at this > > time. And as said in the kernel doc, __platform_driver_probe is > > incompatible with deferred probing. This leads to failure of all > > drivers that needs DMA channels provbided by at_xdmac. > > > > With module_platform_driver, the at_xdmac driver is correctly probed > > again later and all drivers that depends on DMA channels provided by > > this one are also correctly probed. The deferred probing mechanism > > seems to do its job correctly (at least in my case). > > OK would then recommend making it like module_platform_driver ie > remove platform_driver_probe, so the defer probe would work, but keep > the init at subsys level. That should work for you while keeping this > sane for folks that dont need this > Ok, I'll modify it this way, thanks. -- Clément Léger, Embedded Linux and Kernel engineer at Bootlin https://bootlin.com