linux-kernel - Re: [PATCH v7 04/10] scsi: ufs: ufs-qcom: Allow the first init start with the maximum supported gear

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Message-ID: <830f5586-0aec-f2ba-314b-e909f7126248@quicinc.com>
Date:   Fri, 1 Dec 2023 14:51:40 +0530
From:   Nitin Rawat <quic_nitirawa@...cinc.com>
To:     Can Guo <quic_cang@...cinc.com>, <bvanassche@....org>,
        <mani@...nel.org>, <adrian.hunter@...el.com>, <vkoul@...nel.org>,
        <beanhuo@...ron.com>, <avri.altman@....com>,
        <junwoo80.lee@...sung.com>, <martin.petersen@...cle.com>
CC:     <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 v7 04/10] scsi: ufs: ufs-qcom: Allow the first init start
 with the maximum supported gear



On 12/1/2023 10:33 AM, Can Guo wrote:
> During host driver init, the phy_gear is set to the minimum supported gear
> (HS_G2). Then, during the first power mode change, the negotiated gear, say
> HS-G4, is updated to the phy_gear variable so that in the second init the
> updated phy_gear can be used to program the PHY.
> 
> But the current code only allows update the phy_gear to a higher value. If
> one wants to start the first init with the maximum support gear, say HS-G4,
> the phy_gear is not updated to HS-G3 if the device only supports HS-G3.
> 
> The original check added there is intend to make sure the phy_gear won't be
> updated when gear is scaled down (during clock scaling). Update the check
> so that one can start the first init with the maximum support gear without
> breaking the original fix by checking the ufshcd_state, that is, allow
> update to phy_gear only if power mode change is invoked from
> ufshcd_probe_hba().
> 
> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> Signed-off-by: Can Guo <quic_cang@...cinc.com>
> ---
>   drivers/ufs/host/ufs-qcom.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/ufs/host/ufs-qcom.c b/drivers/ufs/host/ufs-qcom.c
> index 9a90019..81056b9 100644
> --- a/drivers/ufs/host/ufs-qcom.c
> +++ b/drivers/ufs/host/ufs-qcom.c
> @@ -916,11 +916,12 @@ static int ufs_qcom_pwr_change_notify(struct ufs_hba *hba,
>   		}
>   
>   		/*
> -		 * Update phy_gear only when the gears are scaled to a higher value. This is
> -		 * because, the PHY gear settings are backwards compatible and we only need to
> -		 * change the PHY gear settings while scaling to higher gears.
> +		 * During UFS driver probe, always update the PHY gear to match the negotiated
> +		 * gear, so that, if quirk UFSHCD_QUIRK_REINIT_AFTER_MAX_GEAR_SWITCH is enabled,
> +		 * the second init can program the optimal PHY settings. This allows one to start
> +		 * the first init with either the minimum or the maximum support gear.
>   		 */
> -		if (dev_req_params->gear_tx > host->phy_gear)
> +		if (hba->ufshcd_state == UFSHCD_STATE_RESET)
>   			host->phy_gear = dev_req_params->gear_tx;
>   
>   		/* enable the device ref clock before changing to HS mode */

Reviewed-by: Nitin Rawat <quic_nitirawa@...cinc.com>