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 Wilczyński" <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()
Date: Mon, 18 Sep 2023 16:14:00 -0500 [thread overview]
Message-ID: <20230918211400.GA208009@bhelgaas> (raw)
In-Reply-To: <ZQWGd/RyKaUBRhUY@smile.fi.intel.com>
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
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prev parent reply other threads:[~2023-09-18 21:14 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-14 19:23 [PATCH v2 1/1] PCI: mediatek: Correct type for virt_to_phys() Andy Shevchenko
2023-09-14 20:31 ` Bjorn Helgaas
2023-09-16 10:41 ` Andy Shevchenko
2023-09-18 21:14 ` Bjorn Helgaas [this message]
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