Re: [PATCH] HID: i2c-hid: add runtime PM support

[Mika Westerberg]

On Tue, Jan 28, 2014 at 09:19:33AM -0500, Benjamin Tissoires wrote:
> On Tue, Jan 28, 2014 at 4:12 AM, Mika Westerberg
> <mika.westerberg@xxxxxxxxxxxxxxx> wrote:
> > On Mon, Jan 27, 2014 at 10:36:25PM -0500, Benjamin Tissoires wrote:
> >> On Tue, Jan 14, 2014 at 5:13 AM, Mika Westerberg
> >> <mika.westerberg@xxxxxxxxxxxxxxx> wrote:
> >> > This patch adds runtime PM support for the HID over I2C driver. When the
> >> > i2c-hid device is first opened we power it on and on the last close we
> >> > power it off.
> >> >
> >> > The implementation is not the most power efficient because it needs some
> >> > interaction from the userspace (e.g close the device node whenever we are
> >> > no more interested in getting events), nevertheless it allows us to save
> >> > some power and works with devices that are not wake capable.
> >> >
> >>
> >> Hi Mika,
> >>
> >> I am a little bit puzzled here. The commit message just says that you
> >> changed the implementation of the power saving with the exact same
> >> behavior...  At least that's what I understand.
> >> Currently, the devices should be put on sleep if nobody is reading,
> >> and back alive if a reader arrives.
> >> I think there is a gain with the patch, but my knowledge of the pm
> >> subsystem is far too limited to see it :(
> >
> > Yes, there should be gain. If there is power domain involved like, ACPI in
> > our case, runtime suspending the device on close will let ACPI to move the
> > device to D3cold (e.g full off) which saves more power.
> 
> Oh, right. So, if you could just put this last sentence in the commit
> message, that would be great.

Sure.

> 
> >
> >> > Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> >> > ---
> >> >  drivers/hid/i2c-hid/i2c-hid.c | 81 ++++++++++++++++++++++++++++---------------
> >> >  1 file changed, 54 insertions(+), 27 deletions(-)
> >> >
> >> > diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
> >> > index d1f81f52481a..ff767d03d60e 100644
> >> > --- a/drivers/hid/i2c-hid/i2c-hid.c
> >> > +++ b/drivers/hid/i2c-hid/i2c-hid.c
> >> > @@ -25,6 +25,7 @@
> >> >  #include <linux/delay.h>
> >> >  #include <linux/slab.h>
> >> >  #include <linux/pm.h>
> >> > +#include <linux/pm_runtime.h>
> >> >  #include <linux/device.h>
> >> >  #include <linux/wait.h>
> >> >  #include <linux/err.h>
> >> > @@ -454,10 +455,18 @@ static void i2c_hid_init_reports(struct hid_device *hid)
> >> >                 return;
> >> >         }
> >> >
> >> > +       /*
> >> > +        * The device must be powered on while we fetch initial reports
> >> > +        * from it.
> >> > +        */
> >> > +       pm_runtime_get_sync(&client->dev);
> >> > +
> >> >         list_for_each_entry(report,
> >> >                 &hid->report_enum[HID_FEATURE_REPORT].report_list, list)
> >> >                 i2c_hid_init_report(report, inbuf, ihid->bufsize);
> >> >
> >> > +       pm_runtime_put(&client->dev);
> >> > +
> >> >         kfree(inbuf);
> >> >  }
> >> >
> >> > @@ -703,8 +712,8 @@ static int i2c_hid_open(struct hid_device *hid)
> >> >
> >> >         mutex_lock(&i2c_hid_open_mut);
> >> >         if (!hid->open++) {
> >> > -               ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
> >> > -               if (ret) {
> >> > +               ret = pm_runtime_get_sync(&client->dev);
> >>
> >> dummy question (kind of late here...). Is there a counter of how many
> >> get/put has been called in pm_runtime which could allow us to get rid
> >> of the hid->open count?
> >
> > There is a counter but I'm not sure if drivers are supposed to use that. I
> > would prefer not to use that.
> 
> ok
> 
> >
> >>
> >> > +               if (ret < 0) {
> >> >                         hid->open--;
> >> >                         goto done;
> >> >                 }
> >> > @@ -712,7 +721,7 @@ static int i2c_hid_open(struct hid_device *hid)
> >> >         }
> >> >  done:
> >> >         mutex_unlock(&i2c_hid_open_mut);
> >> > -       return ret;
> >> > +       return ret < 0 ? ret : 0;
> >> >  }
> >> >
> >> >  static void i2c_hid_close(struct hid_device *hid)
> >> > @@ -729,37 +738,17 @@ static void i2c_hid_close(struct hid_device *hid)
> >> >                 clear_bit(I2C_HID_STARTED, &ihid->flags);
> >> >
> >> >                 /* Save some power */
> >> > -               i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
> >> > +               pm_runtime_put(&client->dev);
> >> >         }
> >> >         mutex_unlock(&i2c_hid_open_mut);
> >> >  }
> >> >
> >> > -static int i2c_hid_power(struct hid_device *hid, int lvl)
> >> > -{
> >> > -       struct i2c_client *client = hid->driver_data;
> >> > -       struct i2c_hid *ihid = i2c_get_clientdata(client);
> >> > -       int ret = 0;
> >> > -
> >> > -       i2c_hid_dbg(ihid, "%s lvl:%d\n", __func__, lvl);
> >> > -
> >> > -       switch (lvl) {
> >> > -       case PM_HINT_FULLON:
> >> > -               ret = i2c_hid_set_power(client, I2C_HID_PWR_ON);
> >> > -               break;
> >> > -       case PM_HINT_NORMAL:
> >> > -               ret = i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
> >> > -               break;
> >> > -       }
> >> > -       return ret;
> >> > -}
> >> > -
> >> >  static struct hid_ll_driver i2c_hid_ll_driver = {
> >> >         .parse = i2c_hid_parse,
> >> >         .start = i2c_hid_start,
> >> >         .stop = i2c_hid_stop,
> >> >         .open = i2c_hid_open,
> >> >         .close = i2c_hid_close,
> >> > -       .power = i2c_hid_power,
> >>
> >> If I understand correctly, here you are trying to fix hidraw (with
> >> i2c_hid tramsport) which used to set_power on/off twice with the first
> >> reader, right?
> >
> > Right.
> >
> >> I don't think we have other i2c_hid users of hid_hw_power, but I am a
> >> little bit worried of simply removing the callback.
> >
> > OK.
> >
> >> What if we just change i2c_hid_set_power in i2c_hid_power by the
> >> corresponding pm_runtime calls?
> >
> > Sure, I'll change that in the next version.
> >
> >>
> >> >         .request = i2c_hid_request,
> >> >  };
> >> >
> >> > @@ -973,13 +962,17 @@ static int i2c_hid_probe(struct i2c_client *client,
> >> >         if (ret < 0)
> >> >                 goto err;
> >> >
> >> > +       pm_runtime_get_noresume(&client->dev);
> >> > +       pm_runtime_set_active(&client->dev);
> >> > +       pm_runtime_enable(&client->dev);
> >> > +
> >> >         ret = i2c_hid_fetch_hid_descriptor(ihid);
> >> >         if (ret < 0)
> >> > -               goto err;
> >> > +               goto err_pm;
> >> >
> >> >         ret = i2c_hid_init_irq(client);
> >> >         if (ret < 0)
> >> > -               goto err;
> >> > +               goto err_pm;
> >> >
> >> >         hid = hid_allocate_device();
> >> >         if (IS_ERR(hid)) {
> >> > @@ -1010,6 +1003,7 @@ static int i2c_hid_probe(struct i2c_client *client,
> >> >                 goto err_mem_free;
> >> >         }
> >> >
> >> > +       pm_runtime_put(&client->dev);
> >> >         return 0;
> >> >
> >> >  err_mem_free:
> >> > @@ -1018,6 +1012,10 @@ err_mem_free:
> >> >  err_irq:
> >> >         free_irq(client->irq, ihid);
> >> >
> >> > +err_pm:
> >> > +       pm_runtime_put_noidle(&client->dev);
> >> > +       pm_runtime_disable(&client->dev);
> >> > +
> >> >  err:
> >> >         i2c_hid_free_buffers(ihid);
> >> >         kfree(ihid);
> >> > @@ -1029,6 +1027,11 @@ static int i2c_hid_remove(struct i2c_client *client)
> >> >         struct i2c_hid *ihid = i2c_get_clientdata(client);
> >> >         struct hid_device *hid;
> >> >
> >> > +       pm_runtime_get_sync(&client->dev);
> >> > +       pm_runtime_disable(&client->dev);
> >> > +       pm_runtime_set_suspended(&client->dev);
> >> > +       pm_runtime_put_noidle(&client->dev);
> >> > +
> >> >         hid = ihid->hid;
> >> >         hid_destroy_device(hid);
> >> >
> >> > @@ -1074,7 +1077,31 @@ static int i2c_hid_resume(struct device *dev)
> >> >  }
> >> >  #endif
> >> >
> >> > -static SIMPLE_DEV_PM_OPS(i2c_hid_pm, i2c_hid_suspend, i2c_hid_resume);
> >> > +#ifdef CONFIG_PM_RUNTIME
> >> > +static int i2c_hid_runtime_suspend(struct device *dev)
> >> > +{
> >> > +       struct i2c_client *client = to_i2c_client(dev);
> >> > +
> >> > +       i2c_hid_set_power(client, I2C_HID_PWR_SLEEP);
> >> > +       disable_irq(client->irq);
> >> > +       return 0;
> >> > +}
> >> > +
> >> > +static int i2c_hid_runtime_resume(struct device *dev)
> >> > +{
> >> > +       struct i2c_client *client = to_i2c_client(dev);
> >> > +
> >> > +       enable_irq(client->irq);
> >> > +       i2c_hid_set_power(client, I2C_HID_PWR_ON);
> >> > +       return 0;
> >> > +}
> >>
> >> These two functions looks very similar to i2c_hid_suspend and
> >> i2c_hid_resume, without the reset and the irq_wake :(
> >> So, my question here is can we use some common code for them?
> >> It may not be possible regarding CONFIG_PM_RUNTIME and
> >> CONFIG_PM_SLEEP, but it still looks ugly to me.
> >
> > It looks ugly, I agree and we can probably reuse some code in the
> > callbacks. I'll look into that.
> 
> well, anyway, if this involve something even more ugly, we can for
> sure stick with this version :)

It turned out that it is going to be ugly, no matter what :-( I'll keep the
current version for now.

> 
> >
> >> I tested this today, and it works, so you should be right, but I'd
> >> like to have your opinion on this.
> >
> > Thanks for testing and comments.
> >
> > I'll prepare a new version with the suggested changes if you are OK with my
> > explanations ;-)
> 
> Sure I am. Thanks for handling the whole ACPI part of this module. I
> was really pleased the other day to see that the touchscreen of a Bay
> trail tablet is now working out of the box :) I still have many other
> problems with this tablet, but still, having the input working is
> always good with a tablet...

If that's the Asus T100 tablet, we are going to fix rest of the problems
soon :-)
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