From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756021AbcHXU43 (ORCPT ); Wed, 24 Aug 2016 16:56:29 -0400 Received: from bhuna.collabora.co.uk ([46.235.227.227]:42508 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751139AbcHXU42 (ORCPT ); Wed, 24 Aug 2016 16:56:28 -0400 Subject: Re: [PACTH,v6,1/2] usb: xhci: plat: Enable runtime PM To: Brian Norris References: <1470861136-23017-2-git-send-email-robert.foss@collabora.com> <20160823032304.GA1781@google.com> Cc: mathias.nyman@intel.com, gregkh@linuxfoundation.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Julius Werner , Andrew Bresticker , Felipe Balbi , Baolin Wang , zyx@rock-chips.com, wulf@rock-chips.com From: Robert Foss Message-ID: <3bf26670-6af5-e580-76cc-304c759befaf@collabora.com> Date: Wed, 24 Aug 2016 16:48:01 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 MIME-Version: 1.0 In-Reply-To: <20160823032304.GA1781@google.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016-08-22 11:23 PM, Brian Norris wrote: > + others > > Hi Robert and Felipe, > > I have a few questions for one or both of you. I'm not really an expert > on runtime PM, so please take my questions with a grain of salt. > > On Wed, Aug 10, 2016 at 04:32:15PM -0400, robert.foss@collabora.com wrote: >> From: Robert Foss >> >> Enable runtime PM for the xhci-plat device so that the parent device >> may implement runtime PM. >> >> Signed-off-by: Robert Foss >> >> Tested-by: Robert Foss >> --- >> drivers/usb/host/xhci-plat.c | 29 +++++++++++++++++++++++++++-- >> 1 file changed, 27 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c >> index ed56bf9..ba4efe7 100644 >> --- a/drivers/usb/host/xhci-plat.c >> +++ b/drivers/usb/host/xhci-plat.c >> @@ -246,6 +246,9 @@ static int xhci_plat_probe(struct platform_device *pdev) >> if (ret) >> goto dealloc_usb2_hcd; >> >> + pm_runtime_set_active(&pdev->dev); >> + pm_runtime_enable(&pdev->dev); >> + > > How does it help to enable PM runtime like this, if you don't have any > kind of runtime_{suspend,resume}() callbacks? Andrew, I think you understand the inner workings of this code better than me, maybe you could give a short summary? > > I suspect that this patch set was derived from the Chromium OS kernel > tree, where we were supporting a Tegra XHCI chipset: > > https://chromium.googlesource.com/chromiumos/third_party/kernel/+/chromeos-3.10/drivers/usb/host/xhci-tegra.c#1920 > > It looks like the driver was refactored to not use xhci-plat.c before it > was upstreamed (and runtime PM support was dropped along the way). > > So, I'm wondering how I might actually use this? Particularly, I'm > looking at trying out runtime suspend for a DWC3 controller in host > mode, and it looks like I'd have to do some layer-violating calls to > xhci_suspend()/xhci_resume() from the parent dwc3 device, or else > rewrite drivers/usb/dwc3/host.c to avoid using xhci-plat.c. > > (I also see that Baolin, CC'd here, was interested in dwc3 [1].) > > Or possibly an enlightening question for me: if you don't mind, how are > you utilizing runtime PM in conjunction with xhci-plat.c, Robert? > Presumably some other parent device/driver is doing some additional > management of the XHCI core? > > Regards, > Brian > > [1] [PATCH 4/4] usb: dwc3: core: Support the dwc3 host suspend/resume > https://lkml.org/lkml/2016/7/15/181 > https://patchwork.kernel.org/patch/9231417/ > >> return 0; >> >> >> @@ -274,6 +277,8 @@ static int xhci_plat_remove(struct platform_device *dev) >> struct xhci_hcd *xhci = hcd_to_xhci(hcd); >> struct clk *clk = xhci->clk; >> >> + pm_runtime_disable(&dev->dev); >> + >> usb_remove_hcd(xhci->shared_hcd); >> usb_phy_shutdown(hcd->usb_phy); >> >> @@ -292,6 +297,13 @@ static int xhci_plat_suspend(struct device *dev) >> { >> struct usb_hcd *hcd = dev_get_drvdata(dev); >> struct xhci_hcd *xhci = hcd_to_xhci(hcd); >> + int ret; >> + >> + ret = pm_runtime_get_sync(dev); >> + if (ret < 0) { >> + pm_runtime_put(dev); >> + return ret; >> + } >> >> /* >> * xhci_suspend() needs `do_wakeup` to know whether host is allowed >> @@ -301,15 +313,28 @@ static int xhci_plat_suspend(struct device *dev) >> * reconsider this when xhci_plat_suspend enlarges its scope, e.g., >> * also applies to runtime suspend. >> */ >> - return xhci_suspend(xhci, device_may_wakeup(dev)); >> + ret = xhci_suspend(xhci, device_may_wakeup(dev)); >> + pm_runtime_put(dev); >> + >> + return ret; >> } >> >> static int xhci_plat_resume(struct device *dev) >> { >> struct usb_hcd *hcd = dev_get_drvdata(dev); >> struct xhci_hcd *xhci = hcd_to_xhci(hcd); >> + int ret; >> >> - return xhci_resume(xhci, 0); >> + ret = pm_runtime_get_sync(dev); >> + if (ret < 0) { >> + pm_runtime_put(dev); >> + return ret; >> + } >> + >> + ret = xhci_resume(xhci, 0); >> + pm_runtime_put(dev); >> + >> + return ret; >> } >> >> static const struct dev_pm_ops xhci_plat_pm_ops = {