linux-kernel - Re: [PATCH v4 1/4] gpu: drm: meson: Use devm_regulator_*get

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Message-ID: <00d90039-c38a-ad8a-80a1-5a654a528756@linaro.org>
Date:   Fri, 21 Oct 2022 17:29:16 +0200
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Matti Vaittinen <mazziesaccount@...il.com>
Cc:     Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Robert Foss <robert.foss@...aro.org>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v4 1/4] gpu: drm: meson: Use devm_regulator_*get_enable*()

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@...il.com>
>>
>> ---
>> 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.

> 
>>   
>>   	meson_dw_hdmi->hdmitx_apb = devm_reset_control_get_exclusive(dev,
>>   						"hdmitx_apb");
> 

Neil