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Date:   Mon, 18 Sep 2023 16:14:00 -0500
From:   Bjorn Helgaas <helgaas@kernel.org>
To:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     linux-pci@vger.kernel.org, linux-mediatek@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        Ryder Lee <ryder.lee@mediatek.com>,
        Jianjun Wang <jianjun.wang@mediatek.com>,
        Lorenzo Pieralisi <lpieralisi@kernel.org>,
        Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= <kw@linux.com>,
        Rob Herring <robh@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        Huacai Chen <chenhuacai@kernel.org>,
        kernel test robot <lkp@intel.com>
Subject: Re: [PATCH v2 1/1] PCI: mediatek: Correct type for virt_to_phys()
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On Sat, Sep 16, 2023 at 01:41:59PM +0300, Andy Shevchenko wrote:
> On Thu, Sep 14, 2023 at 03:31:46PM -0500, Bjorn Helgaas wrote:
> > On Thu, Sep 14, 2023 at 10:23:24PM +0300, Andy Shevchenko wrote:
> 
> ...
> 
> > > -	addr = virt_to_phys(port->base + PCIE_MSI_VECTOR);
> > > +	addr = virt_to_phys((__force void *)port->base + PCIE_MSI_VECTOR);
> > 
> > Lots of these drivers use either virt_to_phys() or
> > platform_get_resource_byname() to get a physical address that they
> > then use as the MSI target.
> > 
> > But I don't think that's quite right -- the MSI is a DMA transaction
> > on PCI, and in general there's no guarantee that bus addresses are
> > identical to CPU physical addresses, so shouldn't we use a dma_addr_t
> > obtained from the DMA API?
> > 
> > dw_pcie_msi_host_init() has a complicated version of this that uses
> > dmam_alloc_coherent().
> 
> Fair enough. I leave it to you then to get it fixed properly.
> Consider this as just a heads up for the old report.

Sounds good, thanks!

Bjorn