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

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Date:   Fri, 23 Sep 2022 14:03:35 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.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

On Thu, 2022-09-22 at 09:17 +0200, AngeloGioacchino Del Regno wrote:
> 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.
Prefer to leave it unchanged, there is no 'const' in
function mtk_phy_update_bits(), if add 'const', will cause build
warning. and FIELD_PREP() already do many checks in compile time.

Thanks

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