linux-kernel - Re: [PATCH v2 3/7] phy: phy-mtk-tphy: add property to set pre-emphasis

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Date:   Thu, 8 Sep 2022 09:39:22 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Vinod Koul <vkoul@...nel.org>, Rob Herring <robh+dt@...nel.org>
CC:     Kishon Vijay Abraham I <kishon@...com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.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>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski@...onical.com>,
        Eddie Hung <eddie.hung@...iatek.com>
Subject: Re: [PATCH v2 3/7] phy: phy-mtk-tphy: add property to set
 pre-emphasis

On Wed, 2022-08-31 at 10:14 +0200, AngeloGioacchino Del Regno wrote:
> Il 29/08/22 10:08, Chunfeng Yun ha scritto:
> > Add a property to set usb2 phy's pre-emphasis, it's disabled by
> > default
> > on some SoCs.
> > 
> > Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> > ---
> > v2: no changes
> > ---
> >   drivers/phy/mediatek/phy-mtk-tphy.c | 10 ++++++++++
> >   1 file changed, 10 insertions(+)
> > 
> > diff --git a/drivers/phy/mediatek/phy-mtk-tphy.c
> > b/drivers/phy/mediatek/phy-mtk-tphy.c
> > index 8ee7682b8e93..986fde0f63a0 100644
> > --- a/drivers/phy/mediatek/phy-mtk-tphy.c
> > +++ b/drivers/phy/mediatek/phy-mtk-tphy.c
> > @@ -72,6 +72,8 @@
> >   #define PA5_RG_U2_HS_100U_U3_EN	BIT(11)
> >   
> >   #define U3P_USBPHYACR6		0x018
> > +#define PA6_RG_U2_PRE_EMP		GENMASK(31, 30)
> > +#define PA6_RG_U2_PRE_EMP_VAL(x)	((0x3 & (x)) << 30)
> 
> Hello Chunfeng,
> 
> can you please clarify which SoC is this change referred to?
These bits are reserved before using 12nm process.

> 
> If I'm not missing anything, there may be a register layout conflict 
As I know these reserved bits are not used before, but now used to tune
pre-emphasis after supporting 12nm or 5nm process.

> between
> one version and the other for T-PHYs, for which, it may be a good
> idea to add
> a PHY version check before allowing to write settings that are
> supported only
> on a specific IP...
Do you know which SoC used bits, I can confirm it with our DE.

Thanks a lot

> 
> Regards,
> Angelo
>