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@xxxxxxxxxxxxx wrote:
From: Robert Foss <robert.foss@xxxxxxxxxxxxx>
Enable runtime PM for the xhci-plat device so that the parent device
may implement runtime PM.
Signed-off-by: Robert Foss <robert.foss@xxxxxxxxxxxxx>
Tested-by: Robert Foss <robert.foss@xxxxxxxxxxxxx>
---
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 = {
--
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