linux-kernel - Re: [PATCH] phy: qcom-qmp-pcie: Fix the SM8450 PCS registers

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Message-ID: <20221026143152.GA93939@thinkpad>
Date:   Wed, 26 Oct 2022 20:01:52 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     vkoul@...nel.org, andersson@...nel.org, kishon@...com,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] phy: qcom-qmp-pcie: Fix the SM8450 PCS registers

On Wed, Sep 21, 2022 at 04:06:10PM +0300, Dmitry Baryshkov wrote:
> On 10/09/2022 09:38, Manivannan Sadhasivam wrote:
> > In the PCS region, registers QPHY_V5_PCS_EQ_CONFIG4 and
> > QPHY_V5_PCS_EQ_CONFIG5 should be used instead of QPHY_V5_PCS_EQ_CONFIG2
> > and QPHY_V5_PCS_EQ_CONFIG3.
> > 
> > This causes high latency when ASPM is enabled, so fix it!
> 
> I have checked against vendor's tree [1]. The registers in question have
> offsets 0x01c0f3e0 / 0x01c0f3e4. The sm8450.dtsi uses 0x1c0f200 as the PCS
> region base for the PCIe PHY1. Thus the correct offsets for the table are
> 0x1e0/0x1e4.
> 
> There might be a mistake in the name of the register, but the address
> corresponds to the address in the vendor's tree.
> 

Right. Only the register name is wrong and I've got the offset wrong here.
But the actual latency issue is fixed by clearing the
QPHY_V4_PCS_PCIE_PRESET_P10_POST register in pcs_misc register space.

I will check with Qcom on this behaviour and post v2 with register name fix.

Thanks,
Mani

> [1] https://github.com/MiCode/kernel_devicetree/blob/zeus-s-oss/qcom/waipio-pcie.dtsi#L520
> 
> > 
> > Fixes: 2c91bf6bf290 ("phy: qcom-qmp: Add SM8450 PCIe1 PHY support")
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >   drivers/phy/qualcomm/phy-qcom-qmp-pcie.c   | 4 ++--
> >   drivers/phy/qualcomm/phy-qcom-qmp-pcs-v5.h | 4 ++--
> >   2 files changed, 4 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> > index 4648467d5cac..b508903d77d0 100644
> > --- a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> > +++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> > @@ -1332,8 +1332,8 @@ static const struct qmp_phy_init_tbl sm8450_qmp_gen4x2_pcie_rx_tbl[] = {
> >   };
> >   static const struct qmp_phy_init_tbl sm8450_qmp_gen4x2_pcie_pcs_tbl[] = {
> > -	QMP_PHY_INIT_CFG(QPHY_V5_PCS_EQ_CONFIG2, 0x16),
> > -	QMP_PHY_INIT_CFG(QPHY_V5_PCS_EQ_CONFIG3, 0x22),
> > +	QMP_PHY_INIT_CFG(QPHY_V5_PCS_EQ_CONFIG4, 0x16),
> > +	QMP_PHY_INIT_CFG(QPHY_V5_PCS_EQ_CONFIG5, 0x22),
> >   	QMP_PHY_INIT_CFG(QPHY_V5_PCS_G3S2_PRE_GAIN, 0x2e),
> >   	QMP_PHY_INIT_CFG(QPHY_V5_PCS_RX_SIGDET_LVL, 0x99),
> >   };
> > diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcs-v5.h b/drivers/phy/qualcomm/phy-qcom-qmp-pcs-v5.h
> > index 61a44519f969..cca6455ec98c 100644
> > --- a/drivers/phy/qualcomm/phy-qcom-qmp-pcs-v5.h
> > +++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcs-v5.h
> > @@ -11,7 +11,7 @@
> >   #define QPHY_V5_PCS_G3S2_PRE_GAIN			0x170
> >   #define QPHY_V5_PCS_RX_SIGDET_LVL			0x188
> >   #define QPHY_V5_PCS_RATE_SLEW_CNTRL1			0x198
> > -#define QPHY_V5_PCS_EQ_CONFIG2				0x1e0
> > -#define QPHY_V5_PCS_EQ_CONFIG3				0x1e4
> > +#define QPHY_V5_PCS_EQ_CONFIG4				0x2e0
> > +#define QPHY_V5_PCS_EQ_CONFIG5				0x2e4
> >   #endif
> 
> -- 
> With best wishes
> Dmitry
> 

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