linux-kernel - Re: [PATCH 2/4] regulator: Introduce Qualcomm REFGEN regulator driver

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Date:   Thu, 29 Jun 2023 10:43:26 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Mark Brown <broonie@...nel.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Krishna Manikandan <quic_mkrishn@...cinc.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org
Subject: Re: [PATCH 2/4] regulator: Introduce Qualcomm REFGEN regulator driver

On 28.06.2023 21:28, Mark Brown wrote:
> On Wed, Jun 28, 2023 at 06:29:46PM +0200, Konrad Dybcio wrote:
> 
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (c) 2017, 2019-2020, The Linux Foundation. All rights reserved.
>> + * Copyright (c) 2023, Linaro Limited
>> + */
> 
> Please use a C++ comment for the whole thing for consistency.
Oh that's new!

> 
>> +static int qcom_sdm845_refgen_enable(struct regulator_dev *rdev)
>> +{
>> +	struct qcom_refgen *vreg = rdev_get_drvdata(rdev);
>> +
>> +	regmap_update_bits(vreg->base, REFGEN_REG_BG_CTRL,
>> +			   REFGEN_BG_CTRL_MASK, REFGEN_BG_CTRL_ENABLE);
>> +	regmap_write(vreg->base, REFGEN_REG_BIAS_EN, REFGEN_BIAS_EN_ENABLE);
> 
> For the enable and disable operations we use a mix of _update_bits() and
> absolute writes with no FIELD_PREP()...
This absolute write was accidentally fine as the mask began at bit0...

> 
>> +static int qcom_sdm845_refgen_is_enabled(struct regulator_dev *rdev)
>> +{
>> +	struct qcom_refgen *vreg = rdev_get_drvdata(rdev);
>> +	u32 val;
>> +
>> +	regmap_read(vreg->base, REFGEN_REG_BG_CTRL, &val);
>> +	if (FIELD_GET(REFGEN_BG_CTRL_MASK, val) != REFGEN_BG_CTRL_ENABLE)
>> +		return 0;
>> +
>> +	regmap_read(vreg->base, REFGEN_REG_BIAS_EN, &val);
>> +	if (FIELD_GET(REFGEN_BIAS_EN_MASK, val) != REFGEN_BIAS_EN_ENABLE)
>> +		return 0;
> 
> ...but when we read back the status we use FIELD_GET().  This looks like
> a bug, and given that one of the fields starts at bit 1 it presumably is
> one - FIELD_GET() will do shifting.
...but a 2-bit-wide field will never equal 6.
Looks like I put unshifted values in the defines for REFGEN_BG_CTRL..

Thanks for spotting that!

> 
>> +static int qcom_sm8250_refgen_enable(struct regulator_dev *rdev)
>> +{
>> +	struct qcom_refgen *vreg = rdev_get_drvdata(rdev);
>> +
>> +	regmap_update_bits(vreg->base, REFGEN_REG_PWRDWN_CTRL5,
>> +			   REFGEN_PWRDWN_CTRL5_MASK, REFGEN_PWRDWN_CTRL5_ENABLE);
> 
> This is a single bit in a single register so could use the standard
> helpers rather than open coding, the sdm845 does need custom operations
> due to having two fields to manage.
Forgot that's a thing!

Konrad