linux-kernel - Re: [PATCH 2/3] usb: xhci: tegra: Add runtime PM support

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Date:   Fri, 9 Mar 2018 09:36:29 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Jon Hunter <jonathanh@...dia.com>
Cc:     Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] usb: xhci: tegra: Add runtime PM support

On Thu, Mar 08, 2018 at 09:31:07PM +0000, Jon Hunter wrote:
> 
> On 01/03/18 14:18, Mathias Nyman wrote:
> > On 14.02.2018 18:34, Jon Hunter wrote:
> >> Add runtime PM support to the Tegra XHCI driver and move the function
> >> calls to enable/disable the clocks, regulators and PHY into the runtime
> >> PM callbacks.
> >>
> >> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
> >> ---
> >>   drivers/usb/host/xhci-tegra.c | 80
> >> ++++++++++++++++++++++++++++++-------------
> >>   1 file changed, 56 insertions(+), 24 deletions(-)
> >>
> >> diff --git a/drivers/usb/host/xhci-tegra.c
> >> b/drivers/usb/host/xhci-tegra.c
> >> index 02b0b24faa58..42aa67858b53 100644
> >> --- a/drivers/usb/host/xhci-tegra.c
> >> +++ b/drivers/usb/host/xhci-tegra.c
> >> @@ -18,6 +18,7 @@
> >>   #include <linux/phy/tegra/xusb.h>
> >>   #include <linux/platform_device.h>
> >>   #include <linux/pm.h>
> >> +#include <linux/pm_runtime.h>
> >>   #include <linux/regulator/consumer.h>
> >>   #include <linux/reset.h>
> >>   #include <linux/slab.h>
> >> @@ -1067,22 +1068,12 @@ static int tegra_xusb_probe(struct
> >> platform_device *pdev)
> >>        */
> >>       platform_set_drvdata(pdev, tegra);
> >>   -    err = tegra_xusb_clk_enable(tegra);
> >> -    if (err) {
> >> -        dev_err(&pdev->dev, "failed to enable clocks: %d\n", err);
> >> -        goto put_usb2;
> >> -    }
> >> -
> >> -    err = regulator_bulk_enable(tegra->soc->num_supplies,
> >> tegra->supplies);
> >> -    if (err) {
> >> -        dev_err(&pdev->dev, "failed to enable regulators: %d\n", err);
> >> -        goto disable_clk;
> >> -    }
> >> +    pm_runtime_enable(&pdev->dev);
> >>   -    err = tegra_xusb_phy_enable(tegra);
> >> +    err = pm_runtime_get_sync(&pdev->dev);
> >>       if (err < 0) {
> > 
> > Does this mean that if runtime PM is disabled then clocks and regulator
> > will never be enabled
> > for Tegra xhci?
> > 
> > How about keeping the clock and regualtor enabling in probe, and instead
> > add something like:
> > 
> > pm_runtime_set_active(&pdev->dev);
> > pm_runtime_enable(&pdev->dev);
> > pm_runtime_get_noresume(&pdev->dev);
> 
> For 64-bit Tegra there is a dependency on CONFIG_PM, but for 32-bit
> AFAIK there is not and so yes we should handle the case when PM_RUNTIME
> is disabled.
> 
> Typically we do something like ...
> 
>     pm_runtime_enable(&pdev->dev);
>     if (!pm_runtime_enabled(&pdev->dev))
> 	ret = tegra_xusb_runtime_resume(&pdev->dev);
>     else
>         ret = pm_runtime_get_sync(&pdev->dev);
> 
> That way we can keep the regulator and clock stuff in the handler. I
> will update this series.

Is there any good reason why we don't depend on PM for 32-bit as well?
I'm not aware of any differences in drivers that are 32-bit specific for
Tegra, and I'm not even sure the !PM case gets any testing at all. And
even if, do we really still want to support that?

I don't see any advantage these days for having it disabled.

Thierry

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