On Jul 25 2023, Douglas Anderson wrote: > As talked about in the patch ("drm/panel: Add a way for other devices > to follow panel state"), we really want to keep the power states of a > touchscreen and the panel it's attached to in sync with each other. In > that spirit, add support to i2c-hid to be a panel follower. This will > let the i2c-hid driver get informed when the panel is powered on and > off. From there we can match the i2c-hid device's power state to that > of the panel. > > NOTE: this patch specifically _doesn't_ use pm_runtime to keep track > of / manage the power state of the i2c-hid device, even though my > first instinct said that would be the way to go. Specific problems > with using pm_runtime(): > * The initial power up couldn't happen in a runtime resume function > since it create sub-devices and, apparently, that's not good to do > in your resume function. > * Managing our power state with pm_runtime meant fighting to make the > right thing happen at system suspend to prevent the system from > trying to resume us only to suspend us again. While this might be > able to be solved, it added complexity. > Overall the code without pm_runtime() ended up being smaller and > easier to understand. > > Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx> > --- > > Changes in v3: > - Add "depends on DRM || !DRM" to Kconfig to avoid randconfig error. > - Split more of the panel follower code out of the core. > > Changes in v2: > - i2c_hid_core_panel_prepared() and ..._unpreparing() are now static. > > drivers/hid/i2c-hid/Kconfig | 2 + > drivers/hid/i2c-hid/i2c-hid-core.c | 82 +++++++++++++++++++++++++++++- > 2 files changed, 82 insertions(+), 2 deletions(-) > > diff --git a/drivers/hid/i2c-hid/Kconfig b/drivers/hid/i2c-hid/Kconfig > index 3be17109301a..2bdb55203104 100644 > --- a/drivers/hid/i2c-hid/Kconfig > +++ b/drivers/hid/i2c-hid/Kconfig > @@ -70,5 +70,7 @@ config I2C_HID_OF_GOODIX > > config I2C_HID_CORE > tristate > + # We need to call into panel code so if DRM=m, this can't be 'y' > + depends on DRM || !DRM > endif > > diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c > index fa8a1ca43d7f..fa6d1f624342 100644 > --- a/drivers/hid/i2c-hid/i2c-hid-core.c > +++ b/drivers/hid/i2c-hid/i2c-hid-core.c > @@ -38,6 +38,8 @@ > #include <linux/mutex.h> > #include <asm/unaligned.h> > > +#include <drm/drm_panel.h> > + > #include "../hid-ids.h" > #include "i2c-hid.h" > > @@ -107,6 +109,8 @@ struct i2c_hid { > struct mutex reset_lock; > > struct i2chid_ops *ops; > + struct drm_panel_follower panel_follower; > + bool is_panel_follower; > }; > > static const struct i2c_hid_quirks { > @@ -1058,6 +1062,59 @@ static int i2c_hid_core_initial_power_up(struct i2c_hid *ihid) > return ret; > } > > +static int i2c_hid_core_panel_prepared(struct drm_panel_follower *follower) > +{ > + struct i2c_hid *ihid = container_of(follower, struct i2c_hid, panel_follower); > + struct hid_device *hid = ihid->hid; > + > + /* > + * hid->version is set on the first power up. If it's still zero then > + * this is the first power on so we should perform initial power up > + * steps. > + */ > + if (!hid->version) > + return i2c_hid_core_initial_power_up(ihid); > + > + return i2c_hid_core_resume(ihid); > +} > + > +static int i2c_hid_core_panel_unpreparing(struct drm_panel_follower *follower) > +{ > + struct i2c_hid *ihid = container_of(follower, struct i2c_hid, panel_follower); > + > + return i2c_hid_core_suspend(ihid); > +} > + > +static const struct drm_panel_follower_funcs i2c_hid_core_panel_follower_funcs = { > + .panel_prepared = i2c_hid_core_panel_prepared, > + .panel_unpreparing = i2c_hid_core_panel_unpreparing, > +}; > + > +static int i2c_hid_core_register_panel_follower(struct i2c_hid *ihid) > +{ > + struct device *dev = &ihid->client->dev; > + int ret; > + > + ihid->is_panel_follower = true; > + ihid->panel_follower.funcs = &i2c_hid_core_panel_follower_funcs; > + > + /* > + * If we're not in control of our own power up/power down then we can't > + * do the logic to manage wakeups. Give a warning if a user thought > + * that was possible then force the capability off. > + */ > + if (device_can_wakeup(dev)) { > + dev_warn(dev, "Can't wakeup if following panel\n"); > + device_set_wakeup_capable(dev, false); > + } > + > + ret = drm_panel_add_follower(dev, &ihid->panel_follower); > + if (ret) > + return ret; > + > + return 0; > +} > + > int i2c_hid_core_probe(struct i2c_client *client, struct i2chid_ops *ops, > u16 hid_descriptor_address, u32 quirks) > { > @@ -1119,7 +1176,15 @@ int i2c_hid_core_probe(struct i2c_client *client, struct i2chid_ops *ops, > hid->bus = BUS_I2C; > hid->initial_quirks = quirks; > > - ret = i2c_hid_core_initial_power_up(ihid); > + /* > + * If we're a panel follower, we'll register and do our initial power > + * up when the panel turns on; otherwise we do it right away. > + */ > + if (drm_is_panel_follower(&client->dev)) > + ret = i2c_hid_core_register_panel_follower(ihid); > + else > + ret = i2c_hid_core_initial_power_up(ihid); nitpicks, but I'm not sure I'm a big fan of having "if (drm_is_panel_follower(&client->dev))" sprinkled everywhere in the generic probe/resume/suspend code. Would it be OK to define a `static int __do_i2c_hid_core_initial_power_up(struct i2c_hid *ihid)` that would do the actual powering up, and have i2c_hid_core_initial_power_up() doing the test if we are a panel follower? The i2c_hid_core_panel_* will need to be updated to use the `__do_` prefixed functions. > + > if (ret) > goto err_mem_free; > > @@ -1143,7 +1208,14 @@ void i2c_hid_core_remove(struct i2c_client *client) > struct i2c_hid *ihid = i2c_get_clientdata(client); > struct hid_device *hid; > > - i2c_hid_core_power_down(ihid); > + /* > + * If we're a follower, the act of unfollowing will cause us to be > + * powered down. Otherwise we need to manually do it. > + */ > + if (ihid->is_panel_follower) > + drm_panel_remove_follower(&ihid->panel_follower); That part is concerning, as we are now calling hid_drv->suspend() when removing the device. It might or not have an impact (I'm not sure of it), but we are effectively changing the path of commands sent to the device. hid-multitouch might call a feature in ->suspend, but the remove makes that the physical is actually disconnected, so the function will fail, and I'm not sure what is happening then. > + else > + i2c_hid_core_power_down(ihid); Same here, I *think* it would be best to have the `if (ihid->is_panel_follower)` test in i2c_hid_core_power_down() (and have a separate _do_i2c_hid_core_power_down()). > > hid = ihid->hid; > hid_destroy_device(hid); > @@ -1171,6 +1243,9 @@ static int i2c_hid_core_pm_suspend(struct device *dev) > struct i2c_client *client = to_i2c_client(dev); > struct i2c_hid *ihid = i2c_get_clientdata(client); > > + if (ihid->is_panel_follower) > + return 0; Not sure we need to split that one with _do_ prefix, it's already split :) > + > return i2c_hid_core_suspend(ihid); > } > > @@ -1179,6 +1254,9 @@ static int i2c_hid_core_pm_resume(struct device *dev) > struct i2c_client *client = to_i2c_client(dev); > struct i2c_hid *ihid = i2c_get_clientdata(client); > > + if (ihid->is_panel_follower) > + return 0; Same here, no need to split. > + > return i2c_hid_core_resume(ihid); > } > > -- > 2.41.0.487.g6d72f3e995-goog > Cheers, Benjamin