Re: [PATCH] soc: amlogic: meson-pwrc: Hold reference returned by of_get_parent()

Re: [PATCH] soc: amlogic: meson-pwrc: Hold reference returned by of_get_parent()

[Neil Armstrong]

+ linux-amlogic, linux-arm-kernel, linux-kernel

On 05/07/2022 04:20, Liang He wrote:
> We should hold the reference returned by of_get_parent() and use
> it to call of_node_put() for refcount balance.
> 
> Signed-off-by: Liang He <windhl@126.com>
> ---
>   drivers/soc/amlogic/meson-ee-pwrc.c     | 5 ++++-
>   drivers/soc/amlogic/meson-gx-pwrc-vpu.c | 5 ++++-
>   2 files changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/soc/amlogic/meson-ee-pwrc.c b/drivers/soc/amlogic/meson-ee-pwrc.c
> index 2be3afe6c2e3..872ab8ba90bc 100644
> --- a/drivers/soc/amlogic/meson-ee-pwrc.c
> +++ b/drivers/soc/amlogic/meson-ee-pwrc.c
> @@ -470,6 +470,7 @@ static int meson_ee_pwrc_probe(struct platform_device *pdev)
>   	const struct meson_ee_pwrc_domain_data *match;
>   	struct regmap *regmap_ao, *regmap_hhi;
>   	struct meson_ee_pwrc *pwrc;
> +	struct device_node *np;
>   	int i, ret;
>   
>   	match = of_device_get_match_data(&pdev->dev);
> @@ -495,7 +496,9 @@ static int meson_ee_pwrc_probe(struct platform_device *pdev)
>   
>   	pwrc->xlate.num_domains = match->count;
>   
> -	regmap_hhi = syscon_node_to_regmap(of_get_parent(pdev->dev.of_node));
> +	np = of_get_parent(pdev->dev.of_node);
> +	regmap_hhi = syscon_node_to_regmap(np);
> +	of_node_put(np);
>   	if (IS_ERR(regmap_hhi)) {
>   		dev_err(&pdev->dev, "failed to get HHI regmap\n");
>   		return PTR_ERR(regmap_hhi);
> diff --git a/drivers/soc/amlogic/meson-gx-pwrc-vpu.c b/drivers/soc/amlogic/meson-gx-pwrc-vpu.c
> index b4615b288625..75a4e1cec416 100644
> --- a/drivers/soc/amlogic/meson-gx-pwrc-vpu.c
> +++ b/drivers/soc/amlogic/meson-gx-pwrc-vpu.c
> @@ -274,6 +274,7 @@ static int meson_gx_pwrc_vpu_probe(struct platform_device *pdev)
>   	struct regmap *regmap_ao, *regmap_hhi;
>   	struct meson_gx_pwrc_vpu *vpu_pd;
>   	struct reset_control *rstc;
> +	struct device_node *np;
>   	struct clk *vpu_clk;
>   	struct clk *vapb_clk;
>   	bool powered_off;
> @@ -291,7 +292,9 @@ static int meson_gx_pwrc_vpu_probe(struct platform_device *pdev)
>   
>   	memcpy(vpu_pd, vpu_pd_match, sizeof(*vpu_pd));
>   
> -	regmap_ao = syscon_node_to_regmap(of_get_parent(pdev->dev.of_node));
> +	np = of_get_parent(pdev->dev.of_node);
> +	regmap_ao = syscon_node_to_regmap(np);
> +	of_node_put(np);
>   	if (IS_ERR(regmap_ao)) {
>   		dev_err(&pdev->dev, "failed to get regmap\n");
>   		return PTR_ERR(regmap_ao);


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Re: [PATCH] soc: amlogic: meson-pwrc: Hold reference returned by of_get_parent()

[Martin Blumenstingl]

Hello,

thank you for your patch!

On Tue, Jul 5, 2022 at 4:20 AM Liang He <windhl@126.com> wrote:
[...]
> +       struct device_node *np;
>
>         int i, ret;
>
>         match = of_device_get_match_data(&pdev->dev);
> @@ -495,7 +496,9 @@ static int meson_ee_pwrc_probe(struct platform_device *pdev)
>
>         pwrc->xlate.num_domains = match->count;
>
> -       regmap_hhi = syscon_node_to_regmap(of_get_parent(pdev->dev.of_node));
> +       np = of_get_parent(pdev->dev.of_node);
> +       regmap_hhi = syscon_node_to_regmap(np);
This works but I had to read the code twice because I thought the
wrong struct device_node was used.
Other drivers typically use "np" for whatever the code section
currently refers to. In this case the code section is about the power
controller, so I thought that "np" was the same as
"pdev->dev.of_node".

I think the code would be easier to understand and the likelihood of
someone making the same mistake as I did if you could rename "np" to
"parent_np" (just like you have done in your other patches).

[...]
> +       struct device_node *np;
same as above, I suggest renaming this to parent_np.

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Re:Re: [PATCH] soc: amlogic: meson-pwrc: Hold reference returned by of_get_parent()

[Liang He]

At 2022-07-26 03:46:30, "Martin Blumenstingl" <martin.blumenstingl@googlemail.com> wrote:
>Hello,
>
>thank you for your patch!
>
>On Tue, Jul 5, 2022 at 4:20 AM Liang He <windhl@126.com> wrote:
>[...]
>> +       struct device_node *np;
>>
>>         int i, ret;
>>
>>         match = of_device_get_match_data(&pdev->dev);
>> @@ -495,7 +496,9 @@ static int meson_ee_pwrc_probe(struct platform_device *pdev)
>>
>>         pwrc->xlate.num_domains = match->count;
>>
>> -       regmap_hhi = syscon_node_to_regmap(of_get_parent(pdev->dev.of_node));
>> +       np = of_get_parent(pdev->dev.of_node);
>> +       regmap_hhi = syscon_node_to_regmap(np);
>This works but I had to read the code twice because I thought the
>wrong struct device_node was used.
>Other drivers typically use "np" for whatever the code section
>currently refers to. In this case the code section is about the power
>controller, so I thought that "np" was the same as
>"pdev->dev.of_node".
>
>I think the code would be easier to understand and the likelihood of
>someone making the same mistake as I did if you could rename "np" to
>"parent_np" (just like you have done in your other patches).
>
>[...]
>> +       struct device_node *np;
>same as above, I suggest renaming this to parent_np.

Thanks, I will send a new verison soon.

Liang
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Re:Re: [PATCH] soc: amlogic: meson-pwrc: Hold reference returned by of_get_parent()

[Liang He]

At 2022-07-26 03:46:30, "Martin Blumenstingl" <martin.blumenstingl@googlemail.com> wrote:
>Hello,
>
>thank you for your patch!
>
>On Tue, Jul 5, 2022 at 4:20 AM Liang He <windhl@126.com> wrote:
>[...]
>> +       struct device_node *np;
>>
>>         int i, ret;
>>
>>         match = of_device_get_match_data(&pdev->dev);
>> @@ -495,7 +496,9 @@ static int meson_ee_pwrc_probe(struct platform_device *pdev)
>>
>>         pwrc->xlate.num_domains = match->count;
>>
>> -       regmap_hhi = syscon_node_to_regmap(of_get_parent(pdev->dev.of_node));
>> +       np = of_get_parent(pdev->dev.of_node);
>> +       regmap_hhi = syscon_node_to_regmap(np);
>This works but I had to read the code twice because I thought the
>wrong struct device_node was used.
>Other drivers typically use "np" for whatever the code section
>currently refers to. In this case the code section is about the power
>controller, so I thought that "np" was the same as
>"pdev->dev.of_node".
>
>I think the code would be easier to understand and the likelihood of
>someone making the same mistake as I did if you could rename "np" to
>"parent_np" (just like you have done in your other patches).
>
>[...]
>> +       struct device_node *np;

>same as above, I suggest renaming this to parent_np.


Hi, Martin,


I notice the declarations keep the reverse Christmas tree order, 
should I keep that order as the  'parent_np' will become longer than 'np'.


Thanks,
Liang
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Re: Re: [PATCH] soc: amlogic: meson-pwrc: Hold reference returned by of_get_parent()

[Martin Blumenstingl]

Hi Liang,

On Tue, Jul 26, 2022 at 3:18 AM Liang He <windhl@126.com> wrote:
[...]
> I notice the declarations keep the reverse Christmas tree order,
> should I keep that order as the  'parent_np' will become longer than 'np'.
Good catch!
Personally I would move parent_np up (above pwrc) to keep the reverse
Christmas tree ordering, even for new variables.


Best regards,
Martin

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