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

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Date:   Wed, 29 Nov 2023 14:04:35 -0500
From:   Eric Chanudet <echanude@...hat.com>
To:     Can Guo <quic_cang@...cinc.com>
Cc:     bvanassche@....org, mani@...nel.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 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?

[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