From: Christoph Hellwig <hch@infradead.org>
To: Peter Geis <pgwipeout@gmail.com>
Cc: Shawn Lin <shawn.lin@rock-chips.com>,
Simon Xue <xxm@rock-chips.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
linux-pci@vger.kernel.org,
"open list:ARM/Rockchip SoC..."
<linux-rockchip@lists.infradead.org>,
devicetree@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
Johan Jonker <jbx6244@gmail.com>,
Heiko Stuebner <heiko@sntech.de>
Subject: Re: [PATCH v7] PCI: rockchip: Add Rockchip RK356X host controller driver
Date: Thu, 29 Apr 2021 07:41:17 +0100 [thread overview]
Message-ID: <20210429064117.GA2214470@infradead.org> (raw)
In-Reply-To: <CAMdYzYr=i7X22-38VyY-GQLWs+aV+ZcWwO_uDymFxmaNO8SpmA@mail.gmail.com>
On Wed, Apr 28, 2021 at 09:42:37PM -0400, Peter Geis wrote:
> I have functional MSI support, some devices do not support MSIs
> however and need legacy INTx.
> I'd like to point out that the downstream patch does not actually work
> on downstream.
> The GFP_DMA32 flag is discarded by the slab allocator, this breaks MSI
> allocation when the PCIe driver probes.
> I hacked together my own version which works but would definitely not
> be accepted for submission.
Seriously folks. Never, ever use GFP_DMA or GFP_DMA32 in actual driver
code. They fundamentally don't do what you want. Devices as a rule of
thumb do care about DMA addressability, not CPU addressability, so they
must use the DMA API to allocate the memory, and the dma mask to control
addressability.
next prev parent reply other threads:[~2021-04-29 6:41 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-14 7:03 [PATCH v7] PCI: rockchip: Add Rockchip RK356X host controller driver Simon Xue
2021-04-28 16:20 ` Peter Geis
[not found] ` <5af0f6f8-bc29-f50e-ca14-94049b7d17ed@rock-chips.com>
2021-04-29 1:42 ` Peter Geis
2021-04-29 6:41 ` Christoph Hellwig [this message]
[not found] ` <CAMdYzYrbfD-jFC3uPVPkhjXWZGeaUw5X=0w1Q=m-6OuhEGOKkQ@mail.gmail.com>
[not found] ` <20210429115451.GA2287423@infradead.org>
2021-04-29 12:16 ` Peter Geis
[not found] ` <3bf6f7ba-d5cb-4857-5fa8-bc4fa0b7e5f6@rock-chips.com>
2021-04-29 11:21 ` Peter Geis
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