From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752699AbeEKJai (ORCPT ); Fri, 11 May 2018 05:30:38 -0400 Received: from mail-pf0-f196.google.com ([209.85.192.196]:39522 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752174AbeEKJaf (ORCPT ); Fri, 11 May 2018 05:30:35 -0400 X-Google-Smtp-Source: AB8JxZrQjnc7geHbbvKzfhMJ/Zt+6vEb0Yz6zhDd8+WoGPSGt5oCVctuFLmHVhsz/jUCAob0qj0DZQ== Subject: Re: [PATCH net] macmace: Set platform device coherent_dma_mask To: Finn Thain , Geert Uytterhoeven References: <0b13a08d-ba2d-b9dc-4fd9-1f6bad5cd1ee@gmail.com> Cc: "David S. Miller" , linux-m68k , netdev , Linux Kernel Mailing List , Christoph Hellwig From: Michael Schmitz X-Enigmail-Draft-Status: N1110 Message-ID: <8c2c3ad5-eeb5-cf61-b9fb-c6096619e310@gmail.com> Date: Fri, 11 May 2018 21:30:26 +1200 User-Agent: Mozilla/5.0 (X11; Linux ppc; rv:45.0) Gecko/20100101 Icedove/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Finn, Am 11.05.2018 um 17:28 schrieb Finn Thain: > On Fri, 11 May 2018, Michael Schmitz wrote: > >> >> I'm afraid using platform_device_register() (which you already use for >> the SCC devices) is the only option handling this on a per-device basis >> without touching platform core code, while at the same time keeping the >> DMA mask setup out of device drivers > > I don't think that will fly. If you call platform_device_register() and > follow that with a dma mask assignment, you could race with the bus > matching and driver probe, and we are back to the same WARNING message. I wasn't proposing to follow platform_device_register() with the mask assignment, but rather to use the same strategy from the Coldfire FEC patch (f61e64310b75): set pdev.dev.coherent_dma_mask and pdev.dev.dma_mask _before_ calling platform_device_register(). > If you want to use platform_device_register(), you'd have to implement > arch_setup_pdev_archdata() and use that to set up the dma mask. If you want to avoid the overhead of defining the macmace platform device and using platform_device_register() ... seeing as you would not be defining just the DMA mask and nothing else, that's probably the least effort for the MACE and SONIC drivers. >> (I can see Geert's point there - device driver code might be shared >> across implementations of the device on platforms with different DMA >> mask requirements,, something the driver can't be expected to know >> about). > > As I said, these drivers might be expected to be portable between Macs and > early PowerMacs, but the same dma mask would apply AFAIK. > > If a platform driver isn't expected to be portable, I think either method > is reasonable: arch_setup_pdev_archdata() or the method in the patch. > > Anyway, there is this in arch/powerpc/kernel/setup-common.c: > > void arch_setup_pdev_archdata(struct platform_device *pdev) > { > pdev->archdata.dma_mask = DMA_BIT_MASK(32); > pdev->dev.dma_mask = &pdev->archdata.dma_mask; > ... You would have to be careful not to overwrite a pdev->dev.dma_mask and pdev->dev.dma_coherent_mask that might have been set in a platform device passed via platform_device_register here. Coldfire is the only m68k platform currently using that, but there might be others in future. > I'm inclined to propose something similar for m68k. That should fix the > problem, since arch_setup_pdev_archdata() is already in the call chain: > > platform_device_register_simple() > platform_device_register_resndata() > platform_device_register_full() > platform_device_alloc() > arch_setup_pdev_archdata() > > Thoughts? Will this have nasty side effects for m68k platforms that use > smaller dma masks? These can still set a smaller mask in pdev->dev directly and use platform_device_register() instead. But I don't think there are smaller DMA masks used by m68k drivers that use the platform device mechanism at present. I've only looked at arch/m68k though. Cheers, Michael