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 10:05:44 +0200
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Chunfeng Yun <chunfeng.yun@...iatek.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

Il 08/09/22 03:39, Chunfeng Yun ha scritto:
> 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.
> 

MT8195, MT8186 (and others), RG_USB20_PHY_REV is marked as bit 31:24.

Regards,
Angelo