From: Niklas Cassel <cassel@kernel.org>
To: Koichiro Den <den@valinux.co.jp>
Cc: "Manivannan Sadhasivam" <mani@kernel.org>,
"Frank Li" <Frank.Li@kernel.org>,
"Krzysztof Wilczyński" <kwilczynski@kernel.org>,
"Kishon Vijay Abraham I" <kishon@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Jonathan Corbet" <corbet@lwn.net>,
"Shuah Khan" <skhan@linuxfoundation.org>,
"Vinod Koul" <vkoul@kernel.org>, "Arnd Bergmann" <arnd@arndb.de>,
"Damien Le Moal" <dlemoal@kernel.org>,
"Marek Vasut" <marek.vasut+renesas@mailbox.org>,
"Yoshihiro Shimoda" <yoshihiro.shimoda.uh@renesas.com>,
linux-pci@vger.kernel.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org
Subject: Re: [PATCH v2 0/3] PCI: endpoint: Add PCI DMA endpoint function (part 3/3)
Date: Mon, 25 May 2026 22:32:06 +0200 [thread overview]
Message-ID: <F31848F5-5481-4402-9B45-9EC7BCC8B0B6@kernel.org> (raw)
In-Reply-To: <3dkicfydmrlm2i6ks34kwjdmlvb22ryftkfw2yj62o4rtj5xvl@f4gby5vlwtdf>
On 25 May 2026 16:03:35 CEST, Koichiro Den <den@valinux.co.jp> wrote:
>On Mon, May 25, 2026 at 10:35:46AM +0200, Niklas Cassel wrote:
>> On Mon, May 25, 2026 at 04:05:02PM +0900, Koichiro Den wrote:
>>
>> If so, but do really all endpoint controllers / endpoint controller drivers
>> support binding to multiple EPFs?
>
>No. For example, R-Car S4's PCIe controller supports multi-functions, while
>RK3588's PCIe controller seems not. So with this scheme, RK3588 would not
>support the NTB transport backed by PCI EP DMA.
I guess it depends on 'max-functions' being set in device tree or not:
https://github.com/torvalds/linux/blob/master/drivers/pci/controller/dwc/pcie-designware-ep.c#L1365-L1367
AFAICT, this value depends on how the DWC PCI controller hardware configuration.
>
>That restriction should be documented with the new NTB transport, which I will
>submit if the direction taken by this series is acceptable.
This is easy for me to say, since I am not the NTB maintainer, but it would be nice if we could somehow come up with a design where we don't only support EPCs that have 'max-functions' != 1, because IIRC, most PCI EPCs have 'max-functions' == 1.
Kind regards,
Nikla
next prev parent reply other threads:[~2026-05-25 20:32 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-25 6:34 [PATCH v2 0/3] PCI: endpoint: Add PCI DMA endpoint function (part 3/3) Koichiro Den
2026-05-25 6:34 ` [PATCH v2 1/3] dmaengine: dw-edma-pcie: Discover endpoint DMA metadata Koichiro Den
2026-05-25 6:34 ` [PATCH v2 2/3] PCI: endpoint: Add DMA endpoint function Koichiro Den
2026-05-25 6:34 ` [PATCH v2 3/3] Documentation: PCI: Add PCI DMA endpoint function documentation Koichiro Den
2026-05-25 18:05 ` Randy Dunlap
2026-05-26 2:18 ` Koichiro Den
2026-05-25 7:05 ` [PATCH v2 0/3] PCI: endpoint: Add PCI DMA endpoint function (part 3/3) Koichiro Den
2026-05-25 8:35 ` Niklas Cassel
2026-05-25 14:03 ` Koichiro Den
2026-05-25 20:32 ` Niklas Cassel [this message]
2026-05-26 2:04 ` Koichiro Den
2026-05-26 5:35 ` Niklas Cassel
2026-05-26 6:23 ` Koichiro Den
2026-05-26 8:28 ` Niklas Cassel
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