linux-kernel - Re: [PATCH v1 1/2] PCI: dwc: drop dependency on ZONE

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Message-ID: <YvUwh1mFpB2WEWdw@google.com>
Date:   Thu, 11 Aug 2022 16:38:31 +0000
From:   William McVicker <willmcvicker@...gle.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, kernel-team@...roid.com,
        Vidya Sagar <vidyas@...dia.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/2] PCI: dwc: drop dependency on ZONE_DMA32

On 08/11/2022, Christoph Hellwig wrote:
> On Tue, Aug 09, 2022 at 06:00:49PM +0000, Will McVicker wrote:
> > Re-work the msi_msg DMA allocation logic to use dma_alloc_coherent()
> > which uses the coherent DMA mask to try and return an allocation within
> > the DMA mask limits. This allows kernel configurations that disable
> > ZONE_DMA32 to continue supporting a 32-bit DMA mask. Without this patch,
> > the PCIe host device will fail to probe when ZONE_DMA32 is disabled.
> 
> > +		dma_free_coherent(dev, PAGE_SIZE, pp->msi_page, pp->msi_data);
> 
> Isn't msi_page a struct page * which should become a void * now?
> 
> Otherwise this looks good and is what the driver should have done
> from the very beginning.

I've updated this in v3 to use dmam_alloc_coherent() and dropped msi_page
since it's not actually used. So this block is dropped now. Thanks for
taking a look though!

--Will