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Tue, 26 Feb 2019 15:44:25 -0800 (PST) Date: Tue, 26 Feb 2019 15:44:23 -0800 From: Brian Norris To: Marc Zyngier Subject: Re: [PATCH 0/4] mwifiex PCI/wake-up interrupt fixes Message-ID: <20190226234422.GD174696@google.com> References: <20190224140426.3267-1-marc.zyngier@arm.com> <5310b73b-4821-6dff-b9c0-34c59fb7fd72@arm.com> <0c433a70-27f6-76ad-c46c-6015de1ffaa4@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <0c433a70-27f6-76ad-c46c-6015de1ffaa4@arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190226_154428_033774_58638DEC X-CRM114-Status: GOOD ( 25.16 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Ganapathi Bhat , Devicetree List , Jeffy Chen , Heiko Stuebner , Ard Biesheuvel , Xinming Hu , "" , linux-pm@vger.kernel.org, "" , Linux Kernel Mailing List , Amitkumar Karwar , linux-rockchip@lists.infradead.org, Nishant Sarmukadam , Rob Herring , linux-arm-kernel , linux-pci@vger.kernel.org, Enric Balletbo i Serra , "David S. Miller" , Kalle Valo Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On Tue, Feb 26, 2019 at 05:14:00PM +0000, Marc Zyngier wrote: > On 26/02/2019 16:21, Ard Biesheuvel wrote: > > On Mon, 25 Feb 2019 at 15:53, Marc Zyngier wrote: > >> It outlines one thing: If you have to interpret per-device PCI > >> properties from DT, you're in for serious trouble. I should get some > >> better HW. > >> > > > > Yeah, it obviously makes no sense at all for the interrupt parent of a > > PCI device to deviate from the host bridge's interrupt parent, and > > it's quite unfortunate that we can't simply ban it now that the cat is > > out of the bag already. > > > > Arguably, the wake up widget is not part of the PCI device, but I have > > no opinion as to whether it is better modeling it as a sub device as > > you are proposing or as an entirely separate device referenced via a > > phandle. > > It is not that clear. The widget seems to be an integral part of the > device, as it is the same basic IP that is used for SDIO and USB. It's not really a widget specific to this IP. It's just a GPIO. It so happens that both SDIO and PCIe designs have wanted to use a GPIO for wakeup, as many other devices do. (Note: it's not just cheap ARM devices; pulling up some Intel Chromebook designs, I see the exact same WAKE# GPIO on their PCIe WiFi as well.) > It looks like the good old pre-PCI-2.2 days, where you had to have a > separate cable between your network card and the base-board for the > wake-up interrupt to be delivered. Starting with PCI-2.2, the bus can > carry the signal just fine. With PCIe, it should just be an interrupt > TLP sent to the RC, but that's obviously not within the capabilities of > the HW. You should search the PCI Express specification for WAKE#. There is a clearly-documented "side-band wake" feature that is part of the standard, as an alternative to in-band TLP wakeup. While you claim this is an ancient thing, it in fact still in use on many systems -- it's just usually abstracted better by ACPI firmware, whereas the dirty laundry is aired a bit more on a Device Tree system. And we got it wrong. > Anyway, it'd be good if the Marvell people could chime in and let us > know how they'd prefer to handle this. I'm not sure this is really a Marvell-specific problem. (Well, except for the marvell,wakeup-pin silliness, which is somewhat orthogonal.) In fact, if we cared a little more about Wake-on-WiFi, we'd be trying to support the same (out-of-band WAKE#) with other WiFi drivers. Brian _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel