Re: [PATCH v4 1/4] gpu: drm: meson: Use devm_regulator_*get_enable*()

[neil.armstrong@xxxxxxxxxx]

On 16/11/2022 13:02, Vaittinen, Matti wrote:
> Hi dee Ho Laurent & All,
>
> On 10/21/22 18:29, Neil Armstrong wrote:
> > Hi,
> >
> > On 21/10/2022 17:02, Laurent Pinchart wrote:
> > > Hi Matti,
> > >
> > > On Fri, Oct 21, 2022 at 04:18:01PM +0300, Matti Vaittinen wrote:
> > > > Simplify using the devm_regulator_get_enable_optional(). Also drop the
> > > > seemingly unused struct member 'hdmi_supply'.
> > > >
> > > > Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>
> > > >
> > > > ---
> > > > v3 => v4:
> > > > - split meson part to own patch
> > > >
> > > > RFCv1 => v2:
> > > > - Change also sii902x to use devm_regulator_bulk_get_enable()
> > > >
> > > > Please note - this is only compile-tested due to the lack of HW. Careful
> > > > review and testing is _highly_ appreciated.
> > > > ---
> > > >    drivers/gpu/drm/meson/meson_dw_hdmi.c | 23 +++--------------------
> > > >    1 file changed, 3 insertions(+), 20 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/meson/meson_dw_hdmi.c
> > > > b/drivers/gpu/drm/meson/meson_dw_hdmi.c
> > > > index 5cd2b2ebbbd3..7642f740272b 100644
> > > > --- a/drivers/gpu/drm/meson/meson_dw_hdmi.c
> > > > +++ b/drivers/gpu/drm/meson/meson_dw_hdmi.c
> > > > @@ -140,7 +140,6 @@ struct meson_dw_hdmi {
> > > >        struct reset_control *hdmitx_apb;
> > > >        struct reset_control *hdmitx_ctrl;
> > > >        struct reset_control *hdmitx_phy;
> > > > -    struct regulator *hdmi_supply;
> > > >        u32 irq_stat;
> > > >        struct dw_hdmi *hdmi;
> > > >        struct drm_bridge *bridge;
> > > > @@ -665,11 +664,6 @@ static void meson_dw_hdmi_init(struct
> > > > meson_dw_hdmi *meson_dw_hdmi)
> > > >    }
> > > > -static void meson_disable_regulator(void *data)
> > > > -{
> > > > -    regulator_disable(data);
> > > > -}
> > > > -
> > > >    static void meson_disable_clk(void *data)
> > > >    {
> > > >        clk_disable_unprepare(data);
> > > > @@ -723,20 +717,9 @@ static int meson_dw_hdmi_bind(struct device
> > > > *dev, struct device *master,
> > > >        meson_dw_hdmi->data = match;
> > > >        dw_plat_data = &meson_dw_hdmi->dw_plat_data;
> > > > -    meson_dw_hdmi->hdmi_supply = devm_regulator_get_optional(dev,
> > > > "hdmi");
> > > > -    if (IS_ERR(meson_dw_hdmi->hdmi_supply)) {
> > > > -        if (PTR_ERR(meson_dw_hdmi->hdmi_supply) == -EPROBE_DEFER)
> > > > -            return -EPROBE_DEFER;
> > > > -        meson_dw_hdmi->hdmi_supply = NULL;
> > > > -    } else {
> > > > -        ret = regulator_enable(meson_dw_hdmi->hdmi_supply);
> > > > -        if (ret)
> > > > -            return ret;
> > > > -        ret = devm_add_action_or_reset(dev, meson_disable_regulator,
> > > > -                           meson_dw_hdmi->hdmi_supply);
> > > > -        if (ret)
> > > > -            return ret;
> > > > -    }
> > > > +    ret = devm_regulator_get_enable_optional(dev, "hdmi");
> > > > +    if (ret != -ENODEV)
> > > > +        return ret;
> > >
> > > As noted in the review of the series that introduced
> > > devm_regulator_get_enable_optional(), the right thing to do is to
> > > implement runtime PM in this driver to avoid wasting power.
> >
> > While I agree, it's not really the same level of effort as this patch
> > should be functionally equivalent.
>
> While we all agree that power savings gained by runtime PM would be
> great - I don't think we should stop minor improvements while waiting
> for that to magically happen ;)
>
> I like the saying I first heard from Jonathan Cameron - "Don't let the
> perfect be an enemy of good".
>
> After that being said, should I re-spin this or just drop it? (I am
> cleaning up my local git from old stuff, and these are about to vanish
> from my books).

I'm ok with you, please re-spin it.

Neil

> Yours,
> 	-- Matti