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From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: Marek Vasut <marek.vasut@gmail.com>
Cc: linux-pci@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Wolfram Sang <wsa@the-dreams.de>,
	Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
	linux-renesas-soc@vger.kernel.org
Subject: Re: [PATCH] PCI: rcar: Always allocate MSI addresses in 32bit space
Date: Mon, 14 Dec 2020 16:08:29 +0000	[thread overview]
Message-ID: <20201214160829.GA3623@e121166-lin.cambridge.arm.com> (raw)
In-Reply-To: <83135f6f-8a98-4537-0df5-91a06af07955@gmail.com>

On Sat, Dec 12, 2020 at 08:13:54PM +0100, Marek Vasut wrote:
> On 12/10/20 7:11 PM, Lorenzo Pieralisi wrote:
> 
> [...]
> 
> > > diff --git a/drivers/pci/controller/pcie-rcar-host.c b/drivers/pci/controller/pcie-rcar-host.c
> > > index 1194d5f3341b..ac5c7d7573a6 100644
> > > --- a/drivers/pci/controller/pcie-rcar-host.c
> > > +++ b/drivers/pci/controller/pcie-rcar-host.c
> > > @@ -753,7 +753,7 @@ static int rcar_pcie_enable_msi(struct rcar_pcie_host *host)
> > >   	}
> > >   	/* setup MSI data target */
> > > -	msi->pages = __get_free_pages(GFP_KERNEL, 0);
> > > +	msi->pages = __get_free_pages(GFP_KERNEL | GFP_DMA32, 0);
> > 
> > This does not do what you want on !CONFIG_ZONE_DMA32 (ie arm LPAE).
> 
> How come? I would expect GFP_DMA32 allocates a buffer below 4 GiB in any
> case.

For ARM LPAE allocation falls back to ZONE_NORMAL that happens to work
because if there is memory > 4GB it ends up in ZONE_HIGHMEM, so this
patch should still work on ARM LPAE too.

Regardless, thoughts above the alternative approach (that saves you
a page allocation) ?

Lorenzo

  reply	other threads:[~2020-12-14 16:09 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-16 12:04 [PATCH] PCI: rcar: Always allocate MSI addresses in 32bit space marek.vasut
2020-10-20  7:47 ` Geert Uytterhoeven
2020-10-25 15:37   ` Marek Vasut
2020-10-27 12:04 ` Yoshihiro Shimoda
2020-12-10 18:11 ` Lorenzo Pieralisi
2020-12-12 19:13   ` Marek Vasut
2020-12-14 16:08     ` Lorenzo Pieralisi [this message]
2020-12-16 17:49       ` Marek Vasut
2020-12-21 10:01         ` Lorenzo Pieralisi
2020-12-30 12:47           ` Marek Vasut
2021-01-04 12:21             ` Lorenzo Pieralisi
2021-01-15 12:12 ` Lorenzo Pieralisi

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