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[46.138.115.62]) by smtp.googlemail.com with ESMTPSA id k24sm505111lfe.76.2021.10.21.10.16.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 Oct 2021 10:16:41 -0700 (PDT) Subject: Re: [PATCH v1] usb: xhci: tegra: Check padctrl interrupt presence in device tree From: Dmitry Osipenko To: Alan Stern Cc: Thierry Reding , Thierry Reding , Jonathan Hunter , Greg Kroah-Hartman , Mathias Nyman , JC Kuo , Nicolas Chauvet , linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org References: <20211021115501.14932-1-digetx@gmail.com> <5f122caa-c810-534d-b2a1-53edef313ff0@gmail.com> <32694811-8768-8e77-f188-4ed1a1fb93da@gmail.com> <20211021152028.GB1161262@rowland.harvard.edu> <82a02e70-33bc-7faf-e085-a25884e48844@gmail.com> Message-ID: <44567c4f-0f0f-6995-b48f-c427cedb6755@gmail.com> Date: Thu, 21 Oct 2021 20:16:40 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <82a02e70-33bc-7faf-e085-a25884e48844@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 21.10.2021 20:13, Dmitry Osipenko пишет: > 21.10.2021 18:20, Alan Stern пишет: >> On Thu, Oct 21, 2021 at 06:08:41PM +0300, Dmitry Osipenko wrote: >>> 21.10.2021 17:57, Dmitry Osipenko пишет: >>>> It might be wrong to disable device_may_wakeup() because it will change >>>> the system suspend-resume behaviour, i.e. you won't be able to resume by >>>> USB event, see [1]. >>>> >>>> [1] >>>> https://elixir.bootlin.com/linux/v5.15-rc6/source/drivers/usb/host/xhci-tegra.c#L1962 >>>> >>>> Although, I'm not sure whether this is a correct behaviour to start >>>> with. Previously, before the offending commit, device_wakeup was never >>>> enabled for tegra-xusb. Commit message doesn't explain why wakeup is now >>>> enabled unconditionally, wakeup checks aren't needed at all then. This >>>> makes no sense, please check it with JC Kuo. >>> >>> Although, wakeup could be disabled via sysfs, so it makes sense. Still >>> it's not clear whether it's a correct behaviour to enable wakeup during >>> system suspend by default. If it wakes machine from suspend when USB >>> device is plugged/unplugged, then it's a wrong behaviour. >> >> It depends on the details of how the device works. In most cases we do >> want to enable wakeup by default for host controller devices. The >> reason is simple enough: If some USB device attached to the HC is >> enabled for wakeup and sends a wakeup request, we don't want the request >> to get lost because the HC isn't allowed to forward the request on to >> the CPU. >> >> But we do not want to enable wakeup for root hubs. In particular, we >> don't want to wake up a suspended system merely because a USB device has >> been plugged or unplugged. >> >> Clearly this arrangement depends on the hardware making a distinction >> between wakeup requests originating from the root hub and those simply >> passing through the HC. > > Should USB keyboard be able to wake up every HC or it's a > machine-specific feature? I mean whether key press should wake up HC if wake-up is enabled for the keyboard device. > I'm asking because wakeup works on a typical > Intel hardware, but doesn't work on older Tegra SoCs that use Chipidea > controller. It's not obvious to me whether this is something that > firmware handles for Intel or it's broken on Tegra. Could you please > clarify? If it should work for every HC, then I may try to take a closer > look. >