linux-kernel - Re: [PATCH 3/4] phy: qcom-qmp: Add optional SW reset

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Date:   Fri, 20 Dec 2019 12:40:15 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Can Guo <cang@...eaurora.org>
Cc:     Asutosh Das <asutoshd@...eaurora.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        linux-arm-msm@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Jeffrey Hugo <jeffrey.l.hugo@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] phy: qcom-qmp: Add optional SW reset

On 20-12-19, 14:00, Can Guo wrote:
> On 2019-12-20 12:24, Vinod Koul wrote:
> > On 20-12-19, 08:49, cang@...eaurora.org wrote:
> > > On 2019-12-20 08:22, cang@...eaurora.org wrote:
> > > > On 2019-12-19 23:04, Vinod Koul wrote:
> > > >
> > > > >  	/* start SerDes and Phy-Coding-Sublayer */
> > > > >  	qphy_setbits(pcs, cfg->regs[QPHY_START_CTRL], cfg->start_ctrl);
> > > 
> > > I thought your change would be like this
> > > 
> > > diff --git a/drivers/phy/qualcomm/phy-qcom-qmp.c
> > > b/drivers/phy/qualcomm/phy-qcom-qmp.c
> > > index 8e642a6..a4ab4b7 100755
> > > --- a/drivers/phy/qualcomm/phy-qcom-qmp.c
> > > +++ b/drivers/phy/qualcomm/phy-qcom-qmp.c
> > > @@ -166,6 +166,7 @@ static const unsigned int
> > > sdm845_ufsphy_regs_layout[] =
> > > {
> > >  };
> > > 
> > >  static const unsigned int sm8150_ufsphy_regs_layout[] = {
> > > +       [QPHY_SW_RESET]                 = 0x08,
> > >         [QPHY_START_CTRL]               = 0x00,
> > >         [QPHY_PCS_READY_STATUS]         = 0x180,
> > >  };
> > > @@ -1390,7 +1391,6 @@ static const struct qmp_phy_cfg
> > > sm8150_ufsphy_cfg = {
> > >         .pwrdn_ctrl             = SW_PWRDN,
> > > 
> > >         .is_dual_lane_phy       = true,
> > > -       .no_pcs_sw_reset        = true,
> > >  };
> > > 
> > >  static void qcom_qmp_phy_configure(void __iomem *base,
> > > @@ -1475,6 +1475,9 @@ static int qcom_qmp_phy_com_init(struct
> > > qmp_phy *qphy)
> > >                              SW_USB3PHY_RESET_MUX | SW_USB3PHY_RESET);
> > >         }
> > > 
> > > +       if ((cfg->type == PHY_TYPE_UFS) && (!cfg->no_pcs_sw_reset))
> > > +               qphy_setbits(pcs, cfg->regs[QPHY_SW_RESET], SW_RESET);
> > 
> > Well am not sure if no_pcs_sw_reset would do this and side effect on
> > other phys (somehow older ones dont seem to need this). That was the
> > reason for a new flag and to be used for specific instances
> > 
> > Thanks
> 
> Hi Vinod,
> 
> That is why I added the check as cfg->type == PHY_TYPE_UFS, meaning this
> change will only apply to UFS.
> FYI, start from 8150(include 8150), QPHY_SW_RESET is present in PHY's
> PCS register. no_pcs_sw_reset = TRUE should only be given to 845 and older
> targets, like 8998, because they don't have this QPHY_SW_RESET in PHY's
> register per their design, that's why they leverage the reset control
> provided by UFS controller.

I have removed no_pcs_sw_reset and tested.

Well as you said even with UFS we have variations between various chips,
so I thought leaving it separate might be better than creating a chance
of regression on older platforms!

Moreover, are we sure that the reset wont be there for other qmp phy's
in future other than UFS...

Thanks
-- 
~Vinod