linux-kernel - Re: [PATCH 01/18] phy: mediatek: add a new helper to update bitfield

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Date:   Thu, 22 Sep 2022 09:17:36 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>,
        Vinod Koul <vkoul@...nel.org>
Cc:     Philipp Zabel <p.zabel@...gutronix.de>,
        Kishon Vijay Abraham I <kishon@...com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        dri-devel@...ts.freedesktop.org,
        linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-phy@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Jitao Shi <jitao.shi@...iatek.com>,
        Stanley Chu <stanley.chu@...iatek.com>
Subject: Re: [PATCH 01/18] phy: mediatek: add a new helper to update bitfield

Il 22/09/22 04:36, Chunfeng Yun ha scritto:
> On Wed, 2022-09-21 at 10:15 +0200, AngeloGioacchino Del Regno wrote:
>> Il 20/09/22 11:00, Chunfeng Yun ha scritto:
>>> Due to FIELD_PREP() macro can be used to prepare a bitfield value,
>>> local ones can be remove; add the new helper to make bitfield
>>> update
>>> easier.
>>>
>>> Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
>>> ---
>>>    drivers/phy/mediatek/phy-mtk-io.h | 7 +++++++
>>>    1 file changed, 7 insertions(+)
>>>
>>> diff --git a/drivers/phy/mediatek/phy-mtk-io.h
>>> b/drivers/phy/mediatek/phy-mtk-io.h
>>> index 500fcdab165d..a723d4afc9b4 100644
>>> --- a/drivers/phy/mediatek/phy-mtk-io.h
>>> +++ b/drivers/phy/mediatek/phy-mtk-io.h
>>> @@ -8,6 +8,7 @@
>>>    #ifndef __PHY_MTK_H__
>>>    #define __PHY_MTK_H__
>>>    
>>> +#include <linux/bitfield.h>
>>>    #include <linux/io.h>
>>>    
>>>    static inline void mtk_phy_clear_bits(void __iomem *reg, u32
>>> bits)
>>> @@ -35,4 +36,10 @@ static inline void mtk_phy_update_bits(void
>>> __iomem *reg, u32 mask, u32 val)
>>>    	writel(tmp, reg);
>>>    }
>>>    
>>> +/* field @mask should be constant and continuous */
>>
>> "Field @mask shall be [...]"
>>                ^^^^^
> Ok, will modify it
> 
>>
>>> +static inline void mtk_phy_update_field(void __iomem *reg, u32
>>> mask, u32 val)
>>
>> ...so, (void __iomem *reg, const u32 mask, u32 val)
> Maybe no need const, @mask will be checked it in compile time when
> use FIELD_PREP(), means @mask is a constant value, but not a variable.
> 

Adding const is not *required*, but `mask` is, effectively, a constant, hence
it fully makes sense to add const.

> Thanks
> 
>>
>>> +{
>>> +	mtk_phy_update_bits(reg, mask, FIELD_PREP(mask, val));
>>> +}
>>> +
>>>    #endif
>>
>>
>