linux-kernel - Re: [PATCH] soc: mediatek: mediatek-regulator-coupler: Fix comment

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Message-ID: <9b12aaec-504c-4e3a-a606-240341d8e0d3@collabora.com>
Date: Wed, 23 Oct 2024 12:40:32 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Fei Shao <fshao@...omium.org>, Matthias Brugger <matthias.bgg@...il.com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] soc: mediatek: mediatek-regulator-coupler: Fix comment

Il 23/10/24 12:19, Fei Shao ha scritto:
> Fix two minor issues in the comments.
> 
> 1. We balance VSRAM voltage based on the target VGPU voltage, so the
>     comment likely refers to VGPU.

Function `mediatek_regulator_balance_voltage()` refers, as stated in the comment
located at the top of its signature, to "GPU<->SRAM" voltages relationships.

So, we're taking into consideration only two regulators:
                   VGPU and VSRAM

The first comment says:
"If we're asked to set a voltage (implicit: to VGPU) less than VSRAM min_uV[...]"

...so, I think that you've misunderstood what the comment says :-)

> 2. .attach_regulator() returns 0 on success and 1 if the regulator is
>     not suitable. The context suggests a successful return value (0).

The comment is on top of a "refuse" or "error" case - one that wants to return 1
and not zero.

Besides, it clearly states:
"The regulator core will keep walking through the list of couplers when any
  .attach_regulator() callback returns 1"

...which is definitely true.

drivers/regulator/core.c
function `regulator_find_coupler()`:

	list_for_each_entry_reverse(coupler, &regulator_coupler_list, list) {
		err = coupler->attach_regulator(coupler, rdev);
		[.....]
		if (err < 0)
			return ERR_PTR(err);

		if (err == 1)
			continue;

		break;
	}

Is that clear now?

Cheers,
Angelo

> 
> Fixes: c200774a6df4 ("soc: mediatek: Introduce mediatek-regulator-coupler driver")
> Signed-off-by: Fei Shao <fshao@...omium.org>
> ---
> 
>   drivers/soc/mediatek/mtk-regulator-coupler.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/soc/mediatek/mtk-regulator-coupler.c b/drivers/soc/mediatek/mtk-regulator-coupler.c
> index 0b6a2884145e..16df12d1c2e0 100644
> --- a/drivers/soc/mediatek/mtk-regulator-coupler.c
> +++ b/drivers/soc/mediatek/mtk-regulator-coupler.c
> @@ -74,7 +74,7 @@ static int mediatek_regulator_balance_voltage(struct regulator_coupler *coupler,
>   		return ret;
>   
>   	/*
> -	 * If we're asked to set a voltage less than VSRAM min_uV, set
> +	 * If we're asked to set a voltage less than VGPU min_uV, set
>   	 * the minimum allowed voltage on VSRAM, as in this case it is
>   	 * safe to ignore the max_spread parameter.
>   	 */
> @@ -108,7 +108,7 @@ static int mediatek_regulator_attach(struct regulator_coupler *coupler,
>   	 * this means that this is surely not a GPU<->SRAM couple: in that
>   	 * case, we may want to use another coupler implementation, if any,
>   	 * or the generic one: the regulator core will keep walking through
> -	 * the list of couplers when any .attach_regulator() cb returns 1.
> +	 * the list of couplers when any .attach_regulator() cb returns 0.
>   	 */
>   	if (rdev->coupling_desc.n_coupled > 2)
>   		return 1;