linux-kernel - Re: [PATCH v6 10/10] scsi: ufs: ufs-qcom: Add support for UFS device version detection

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Date:   Thu, 30 Nov 2023 12:58:59 +0530
From:   Manivannan Sadhasivam <mani@...nel.org>
To:     Eric Chanudet <echanude@...hat.com>
Cc:     Can Guo <quic_cang@...cinc.com>, bvanassche@....org,
        adrian.hunter@...el.com, cmd4@...lcomm.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,
        "Bao D. Nguyen" <quic_nguyenb@...cinc.com>,
        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 v6 10/10] scsi: ufs: ufs-qcom: Add support for UFS device
 version detection

On Wed, Nov 29, 2023 at 02:04:35PM -0500, Eric Chanudet wrote:
> On Wed, Nov 29, 2023 at 12:28:35AM -0800, Can Guo wrote:
> > From: "Bao D. Nguyen" <quic_nguyenb@...cinc.com>
> > 
> > A spare register in UFS host controller is used to indicate the UFS device
> > version. The spare register is populated by bootloader for now, but in
> > future it will be populated by HW automatically during link startup with
> > its best efforts in any boot stages prior to Linux.
> > 
> > During host driver init, read the spare register, if it is not populated
> > with a UFS device version, go ahead with the dual init mechanism. If a UFS
> > device version is in there, use the UFS device version together with host
> > controller's HW version to decide the proper PHY gear which should be used
> > to configure the UFS PHY without going through the second init.
> > 
> > Signed-off-by: Bao D. Nguyen <quic_nguyenb@...cinc.com>
> > Signed-off-by: Can Guo <quic_cang@...cinc.com>
> > ---
> >  drivers/ufs/host/ufs-qcom.c | 23 ++++++++++++++++++-----
> >  drivers/ufs/host/ufs-qcom.h |  2 ++
> >  2 files changed, 20 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> > index 9c0ebbc..e94dea2 100644
> > --- a/drivers/ufs/host/ufs-qcom.c
> > +++ b/drivers/ufs/host/ufs-qcom.c
> > @@ -1068,15 +1068,28 @@ static void ufs_qcom_advertise_quirks(struct ufs_hba *hba)
> >  static void ufs_qcom_set_phy_gear(struct ufs_qcom_host *host)
> >  {
> >  	struct ufs_host_params *host_params = &host->host_params;
> > +	u32 val, dev_major = 0;
> >  
> >  	host->phy_gear = host_params->hs_tx_gear;
> >  
> > -	/*
> > -	 * Power up the PHY using the minimum supported gear (UFS_HS_G2).
> > -	 * Switching to max gear will be performed during reinit if supported.
> > -	 */
> > -	if (host->hw_ver.major < 0x4)
> > +	if (host->hw_ver.major < 0x4) {
> > +		/*
> > +		 * Power up the PHY using the minimum supported gear (UFS_HS_G2).
> > +		 * Switching to max gear will be performed during reinit if supported.
> > +		 */
> >  		host->phy_gear = UFS_HS_G2;
> > +	} else {
> > +		val = ufshcd_readl(host->hba, REG_UFS_DEBUG_SPARE_CFG);
> > +		dev_major = FIELD_GET(GENMASK(7, 4), val);
> > +
> > +		/* UFS device version populated, no need to do init twice */
> 
> This change documents the content of the register as "UFS device
> version", both inline in the code and in the commit description. Earlier
> in this series[1], Mani mentioned it was the gear info:
> > > [...]populating a spare register in the bootloader with the max gear
> > > info that the bootloader has already found[...]
> 
> Is it the gear number as in HS-G4? Or the version as in UFS controller
> revision 3.1?
> 

That was a mistake from my end, apologies. The register has the device version
only and the driver uses both device and host controller's version info to
decide the initial gear.

- Mani

> [1] https://lore.kernel.org/all/20231018124741.GA47321@thinkpad/
> 
> > +		if (dev_major != 0)
> > +			host->hba->quirks &= ~UFSHCD_QUIRK_REINIT_AFTER_MAX_GEAR_SWITCH;
> > +
> > +		/* For UFS 3.1 and older, apply HS-G4 PHY gear to save power */
> > +		if (dev_major < 0x4 && dev_major > 0)
> > +			host->phy_gear = UFS_HS_G4;
> > +	}
> >  }
> >  
> >  static void ufs_qcom_set_host_params(struct ufs_hba *hba)
> > diff --git a/drivers/ufs/host/ufs-qcom.h b/drivers/ufs/host/ufs-qcom.h
> > index 11419eb..d12fc5a 100644
> > --- a/drivers/ufs/host/ufs-qcom.h
> > +++ b/drivers/ufs/host/ufs-qcom.h
> > @@ -54,6 +54,8 @@ enum {
> >  	UFS_AH8_CFG				= 0xFC,
> >  
> >  	REG_UFS_CFG3				= 0x271C,
> > +
> > +	REG_UFS_DEBUG_SPARE_CFG			= 0x284C,
> >  };
> >  
> >  /* QCOM UFS host controller vendor specific debug registers */
> > -- 
> > 2.7.4
> > 
> > 
> 
> -- 
> Eric Chanudet
> 
> 

-- 
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