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Date: Tue, 28 Jan 2014 09:19:33 -0500
From: Benjamin Tissoires <benjamin.tissoires@...il.com>
To: Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc: linux-input <linux-input@...r.kernel.org>,
Jiri Kosina <jkosina@...e.cz>,
Benjamin Tissoires <benjamin.tissoires@...hat.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] HID: i2c-hid: add runtime PM support
On Tue, Jan 28, 2014 at 4:12 AM, Mika Westerberg
<mika.westerberg@...ux.intel.com> 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@...ux.intel.com> 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.
>
>> > Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
>> > ---
>> > 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 :)
>
>> 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...
Cheers,
Benjamin
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