linux-kernel - Re: [PATCH v2 3/5] phy: mediatek: add helpers to update bits of registers

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Date:   Mon, 3 Jan 2022 09:59:04 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Vinod Koul <vkoul@...nel.org>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Eddie Hung <eddie.hung@...iatek.com>
Subject: Re: [PATCH v2 3/5] phy: mediatek: add helpers to update bits of
 registers

Il 30/12/21 03:06, Chunfeng Yun ha scritto:
> On Fri, 2021-12-24 at 11:10 +0100, AngeloGioacchino Del Regno wrote:
>> Il 18/12/21 09:28, Chunfeng Yun ha scritto:
>>> Add three helpers mtk_phy_clear/set/update_bits() for registers
>>> operation
>>>
>>> Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
>>> ---
>>> v2: new patch, add register access helpers,
>>>       Add updatel() macro suggested by Vinod, here add more ones
>>> instead.
>>> ---
>>>    drivers/phy/mediatek/phy-mtk-io.h | 38
>>> +++++++++++++++++++++++++++++++
>>>    1 file changed, 38 insertions(+)
>>>    create mode 100644 drivers/phy/mediatek/phy-mtk-io.h
>>>
>>> diff --git a/drivers/phy/mediatek/phy-mtk-io.h
>>> b/drivers/phy/mediatek/phy-mtk-io.h
>>> new file mode 100644
>>> index 000000000000..500fcdab165d
>>> --- /dev/null
>>> +++ b/drivers/phy/mediatek/phy-mtk-io.h
>>> @@ -0,0 +1,38 @@
>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>> +/*
>>> + * Copyright (C) 2021 MediaTek Inc.
>>> + *
>>> + * Author: Chunfeng Yun <chunfeng.yun@...iatek.com>
>>> + */
>>> +
>>> +#ifndef __PHY_MTK_H__
>>> +#define __PHY_MTK_H__
>>> +
>>> +#include <linux/io.h>
>>> +
>>> +static inline void mtk_phy_clear_bits(void __iomem *reg, u32 bits)
>>> +{
>>> +	u32 tmp = readl(reg);
>>> +
>>> +	tmp &= ~bits;
>>> +	writel(tmp, reg);
>>> +}
>>> +
>>> +static inline void mtk_phy_set_bits(void __iomem *reg, u32 bits)
>>> +{
>>> +	u32 tmp = readl(reg);
>>> +
>>> +	tmp |= bits;
>>> +	writel(tmp, reg);
>>> +}
>>> +
>>> +static inline void mtk_phy_update_bits(void __iomem *reg, u32
>>> mask, u32 val)
>>> +{
>>> +	u32 tmp = readl(reg);
>>> +
>>> +	tmp &= ~mask;
>>> +	tmp |= val & mask;
>>> +	writel(tmp, reg);
>>> +}
>>> +
>>> +#endif
>>>
>>
>> These helpers are almost exactly duplicating what
>> regmap_update_bits() is doing.
>> I appreciate the effort to stop open-coding the same sequences over
>> and over by
>> adding such helper functions,
> I agree with you.
>> but I think that the proper way of doing what you
>> are proposing is not to add custom functions but rather reuse what
>> the Linux APIs
>> give you.
> I also like to use common APIs ASAP, but not found suitable ones.
> This may be a problem, I found that some similar custom helps already
> added under phy fold.
> 
>>
>> What about doing a conversion to use regmap on this driver?
> No, we don't use regmap here, these registers are monopolized by t-phy,
> it's not syscon.
> 
> 

Hello,

The regmap API allows this kind of usage, registers don't necessarily have
to be part of a syscon.

Regards,
- Angelo