Re: [PATCH 3/3] PM: domains: Add a ->dev_get_performance_state() callback to genpd
From: Ulf Hansson <hidden>
Date: 2021-09-03 08:56:20
Also in:
linux-pm, lkml
On Fri, 3 Sept 2021 at 08:00, Dmitry Osipenko [off-list ref] wrote:
02.09.2021 13:16, Ulf Hansson пишет:quoted
Hardware may be preprogrammed to a specific performance state, which may not be zero initially during boot. This may lead to that genpd's current performance state becomes inconsistent with the state of the hardware. To deal with this, the driver for a device that is being attached to its genpd, need to request an initial performance state vote, which is typically done by calling some of the OPP APIs while probing. In some cases this would lead to boilerplate code in the drivers. Let's make it possible to avoid this, by adding a new optional callback to genpd and invoke it per device during the attach process. In this way, the genpd provider driver can inform genpd about the initial performance state that is needed for the device. Signed-off-by: Ulf Hansson <redacted> --- drivers/base/power/domain.c | 8 +++++--- include/linux/pm_domain.h | 2 ++ 2 files changed, 7 insertions(+), 3 deletions(-)diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c index 800adf831cae..1a6f3538af8d 100644 --- a/drivers/base/power/domain.c +++ b/drivers/base/power/domain.c@@ -2640,13 +2640,15 @@ static void genpd_dev_pm_sync(struct device *dev) genpd_queue_power_off_work(pd); } -static int genpd_get_default_performance_state(struct device *dev, +static int genpd_get_default_performance_state(struct generic_pm_domain *genpd, + struct device *dev, unsigned int index) { int pstate = of_get_required_opp_performance_state(dev->of_node, index); if (pstate == -ENODEV || pstate == -EOPNOTSUPP) - return 0; + pstate = genpd->dev_get_performance_state ? + genpd->dev_get_performance_state(genpd, dev) : 0; return pstate; }@@ -2701,7 +2703,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev, } /* Set the default performance state */ - pstate = genpd_get_default_performance_state(dev, index); + pstate = genpd_get_default_performance_state(pd, dev, index);If base device is suspended, then its performance state is zero. When device will be rpm-resumed, then its performance should be set to the default state. You're setting performance state of the wrong device, it should be the base device and not the virtual domain device.
No I am not. :-) Let me elaborate.
For the single PM domain case, 'dev' and 'base_dev' are pointing to
the same device. So this works fine.
For the multiple PM domain case or when attaching goes via
genpd_dev_pm_attach_by_id(), 'dev' is the virtual device registered in
genpd_dev_pm_attach_by_id(). In this case, it's 'dev' that is becoming
attached to genpd and not the 'base_dev'. Note also that, runtime PM
has not been enabled for 'dev' yet at this point and 'dev' has been
assigned the same OF node as 'base_dev", to allow OF parsing to work
as is for it.
Moreover, to deal with runtime PM in the multiple PM domain case, the
consumer driver should create a device link. Along the lines of this:
device_link_add(base_dev, dev, DL_FLAG_PM_RUNTIME |
DL_FLAG_STATELESS), thus assigning the virtual device ('dev') as the
supplier for its consumer device ('base_dev').
These all is handled properly by my patch [1]. Hence it's complicated for the reason.
See above. It shouldn't have to be complicated. If it still is, there is something to fix for the multiple PM domain case.
[1] https://patchwork.ozlabs.org/project/linux-tegra/patch/20210831135450.26070-5-digetx@gmail.com/
Kind regards Uffe _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel