linux-kernel - Re: [PATCH v2] phy: ti: phy-j721e-wiz: fix usxgmii configuration

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Message-ID: <c5ef5303-6390-4f2b-b9d2-3d1f3085e15f@ti.com>
Date: Tue, 1 Oct 2024 08:40:27 +0530
From: Siddharth Vadapalli <s-vadapalli@...com>
To: Roger Quadros <rogerq@...nel.org>
CC: Siddharth Vadapalli <s-vadapalli@...com>, <vkoul@...nel.org>,
        <kishon@...nel.org>, <thomas.richard@...tlin.com>,
        <krzysztof.kozlowski@...aro.org>, <nichen@...as.ac.cn>,
        <c-vankar@...com>, <t-patil@...com>, <linux-phy@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <srk@...com>
Subject: Re: [PATCH v2] phy: ti: phy-j721e-wiz: fix usxgmii configuration

On Mon, Sep 30, 2024 at 05:06:35PM +0300, Roger Quadros wrote:

Hello Roger,

> Hi Siddharth,
> 
> On 30/09/2024 12:57, Siddharth Vadapalli wrote:
> > Commit b64a85fb8f53 ("phy: ti: phy-j721e-wiz.c: Add usxgmii support in
> > wiz driver") added support for USXGMII mode. In doing so, P0_REFCLK_SEL
> > was set to "pcs_mac_clk_divx1_ln_0" (0x3) and P0_STANDARD_MODE was set to
> > LANE_MODE_GEN1, which results in a data rate of 5.15625 Gbps. However,
> > since the USXGMII mode can support up to 10.3125 Gbps data rate, the
> > aforementioned fields should be set to "pcs_mac_clk_divx0_ln_0" (0x2) and
> > LANE_MODE_GEN2 respectively. Fix the configuration accordingly to truly
> > support USXGMII up to 10G.
> > 
> > Fixes: b64a85fb8f53 ("phy: ti: phy-j721e-wiz.c: Add usxgmii support in wiz driver")
> > Signed-off-by: Siddharth Vadapalli <s-vadapalli@...com>

[...]

> > diff --git a/drivers/phy/ti/phy-j721e-wiz.c b/drivers/phy/ti/phy-j721e-wiz.c
> > index a6c0c5607ffd..c6e846d385d2 100644
> > --- a/drivers/phy/ti/phy-j721e-wiz.c
> > +++ b/drivers/phy/ti/phy-j721e-wiz.c
> > @@ -450,8 +450,8 @@ static int wiz_mode_select(struct wiz *wiz)
> >  		} else if (wiz->lane_phy_type[i] == PHY_TYPE_USXGMII) {
> >  			ret = regmap_field_write(wiz->p0_mac_src_sel[i], 0x3);
> >  			ret = regmap_field_write(wiz->p0_rxfclk_sel[i], 0x3);
> 
> I'm not sure. Don't we have to change rxfclk as well?

This patch was validated on a custom board with the J7200 SR 2.0 SoC.
The signal corresponding to the USXGMII lane of the SERDES was measured
to be 5 Gbps without this patch and 10 Gbps with this patch applied,
with no other changes required. Apart from measuring the signal, ping
was also validated.

Regards,
Siddharth.