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

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Message-ID: <a8eef2d5-5ac5-45bb-97ba-1d6acd5a6a5c@quicinc.com>
Date:   Thu, 30 Nov 2023 16:21:39 +0800
From:   Can Guo <quic_cang@...cinc.com>
To:     Manivannan Sadhasivam <mani@...nel.org>
CC:     <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 11/30/2023 3:25 PM, Manivannan Sadhasivam 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;
> 
> No need to initialize dev_major.

True.

> 
>>   
>>   	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 {
> 
> Can you please add a comment here to describe what is happening?

Will do.

> 
>> +		val = ufshcd_readl(host->hba, REG_UFS_DEBUG_SPARE_CFG);
>> +		dev_major = FIELD_GET(GENMASK(7, 4), val);
> 
> It'd be good to add a macro for GENMASK().

OK

> 
>> +
>> +		/* UFS device version populated, no need to do init twice */
> 
> "Since the UFS device version is populated, let's remove the REINIT quirk as the
> negotiated gear won't change during boot. So there is no need to do reinit."
> 

Nice comment.

>> +		if (dev_major != 0)
> 
> 0x0

Done

> 
>> +			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)
> 
> if (dev_major > 0x0 && dev_major < 0x4)
> 

Sure.

Thanks,
Can Guo.

> - Mani
> 
>> +			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
>>
>>
>