linux-kernel - Re: [PATCH v5 06/10] scsi: ufs: ufs-qcom: Limit HS-G5 Rate-A to hosts with HW version 5

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Message-ID: <20231128112409.GU3088@thinkpad>
Date:   Tue, 28 Nov 2023 16:54:09 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Can Guo <quic_cang@...cinc.com>
Cc:     bvanassche@....org, adrian.hunter@...el.com, beanhuo@...ron.com,
        avri.altman@....com, junwoo80.lee@...sung.com,
        martin.petersen@...cle.com, linux-scsi@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 06/10] scsi: ufs: ufs-qcom: Limit HS-G5 Rate-A to
 hosts with HW version 5

On Tue, Nov 28, 2023 at 06:59:39PM +0800, Can Guo wrote:
> 
> 
> On 11/28/2023 6:55 PM, Manivannan Sadhasivam wrote:
> > On Tue, Nov 28, 2023 at 03:48:02PM +0800, Can Guo wrote:
> > > Hi Mani,
> > > 
> > > On 11/28/2023 1:55 PM, Manivannan Sadhasivam wrote:
> > > > On Thu, Nov 23, 2023 at 12:46:26AM -0800, Can Guo wrote:
> > > > > Qcom UFS hosts, with HW ver 5, can only support up to HS-G5 Rate-A due to
> > > > > HW limitations. If the HS-G5 PHY gear is used, update host_params->hs_rate
> > > > > to Rate-A, so that the subsequent power mode changes shall stick to Rate-A.
> > > > > 
> > > > > Signed-off-by: Can Guo <quic_cang@...cinc.com>
> > > > 
> > > > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > > > 
> > > > One question below...
> > > > 
> > > > > ---
> > > > >    drivers/ufs/host/ufs-qcom.c | 18 +++++++++++++++++-
> > > > >    1 file changed, 17 insertions(+), 1 deletion(-)
> > > > > 
> > > > > diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> > > > > index 9613ad9..6756f8d 100644
> > > > > --- a/drivers/ufs/host/ufs-qcom.c
> > > > > +++ b/drivers/ufs/host/ufs-qcom.c
> > > > > @@ -442,9 +442,25 @@ static u32 ufs_qcom_get_hs_gear(struct ufs_hba *hba)
> > > > >    static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
> > > > >    {
> > > > >    	struct ufs_qcom_host *host = ufshcd_get_variant(hba);
> > > > > +	struct ufs_host_params *host_params = &host->host_params;
> > > > >    	struct phy *phy = host->generic_phy;
> > > > > +	enum phy_mode mode;
> > > > >    	int ret;
> > > > > +	/*
> > > > > +	 * HW ver 5 can only support up to HS-G5 Rate-A due to HW limitations.
> > > > > +	 * If the HS-G5 PHY gear is used, update host_params->hs_rate to Rate-A,
> > > > > +	 * so that the subsequent power mode change shall stick to Rate-A.
> > > > > +	 */
> > > > > +	if (host->hw_ver.major == 0x5) {
> > > > > +		if (host->phy_gear == UFS_HS_G5)
> > > > > +			host_params->hs_rate = PA_HS_MODE_A;
> > > > > +		else
> > > > > +			host_params->hs_rate = PA_HS_MODE_B;
> > > > 
> > > > Is this 'else' part really needed? Since there wouldn't be any 2nd init, I think
> > > > we can skip that.
> > > 
> > > We need it because, even there is only one init, if a UFS3.1 device is
> > > attached, phy_gear is given as UFS_HS_G4 in ufs_qcom_set_phy_gear(), hence
> > > we need to put the UFS at HS-G4 Rate B, not Rate A.
> > > 
> > 
> > But the default hs_rate is PA_HS_MODE_B only and the else condition would be not
> > needed for the 1st init.
> 
> You are right, but still we need this in case the UFS device version is not
> populated, meaning dual init can also happen to SM8550. We need to apply the
> right hs_rate in case the 2nd init asks for HS_G4.
> 

Hmm, yeah I missed that corner case. This is fine.

- Mani

> Thanks,
> Can Guo.
> 
> > 
> > - Mani
> > 
> > > Thanks,
> > > Can Guo.
> > > 
> > > > 
> > > > - Mani
> > > > 
> > > > > +	}
> > > > > +
> > > > > +	mode = host_params->hs_rate == PA_HS_MODE_B ? PHY_MODE_UFS_HS_B : PHY_MODE_UFS_HS_A;
> > > > > +
> > > > >    	/* Reset UFS Host Controller and PHY */
> > > > >    	ret = ufs_qcom_host_reset(hba);
> > > > >    	if (ret)
> > > > > @@ -459,7 +475,7 @@ static int ufs_qcom_power_up_sequence(struct ufs_hba *hba)
> > > > >    		return ret;
> > > > >    	}
> > > > > -	phy_set_mode_ext(phy, PHY_MODE_UFS_HS_B, host->phy_gear);
> > > > > +	phy_set_mode_ext(phy, mode, host->phy_gear);
> > > > >    	/* power on phy - start serdes and phy's power and clocks */
> > > > >    	ret = phy_power_on(phy);
> > > > > -- 
> > > > > 2.7.4
> > > > > 
> > > > 
> > 

-- 
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