linux-kernel - RE: [PATCH] scsi: ufs: no sw reset after last linkstartup fail

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Date:   Mon, 4 Jul 2022 20:11:25 +0900
From:   "Seunghui Lee" <sh043.lee@...sung.com>
To:     <alim.akhtar@...sung.com>, <avri.altman@....com>,
        <bvanassche@....org>, <jejb@...ux.ibm.com>,
        <martin.petersen@...cle.com>, <linux-scsi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Cc:     <grant.jung@...sung.com>, <jt77.jang@...sung.com>,
        <dh0421.hwang@...sung.com>, <junwoo80.lee@...sung.com>,
        <jangsub.yi@...sung.com>, <cw9316.lee@...sung.com>,
        <sh8267.baek@...sung.com>, <wkon.kim@...sung.com>,
        <seunghwan.hyun@...sung.com>
Subject: RE: [PATCH] scsi: ufs: no sw reset after last linkstartup fail

As we know, the ufs host controller is disabled and enabled in the ufshcd_hba_enable(). So, host controller registers are clear after sw reset.

Once the host fails to link startup 3 times, all host's controller can be clear due to executing last ufshcd_hba_enable()(s/w reset).
That's why we need to skip last sw reset to get valid host register values.

Before
(ufshcd_dme_link_startup() -> ufshcd_hba_enable() -> retries--) * 3 times.

After
(ufshcd_dme_link_startup() -> if retries is 0, break. ->  ufshcd_hba_enable() -> retries--) * 3 times.
In this case, ufshcd_print_host_state(), ufshcd_print_pwr_info(), ufshcd_print_evt_hist() are valid.

> -----Original Message-----
> From: Seunghui Lee <sh043.lee@...sung.com>
> Sent: Thursday, June 30, 2022 1:48 PM
> To: alim.akhtar@...sung.com; avri.altman@....com; bvanassche@....org;
> jejb@...ux.ibm.com; martin.petersen@...cle.com; linux-scsi@...r.kernel.org;
> linux-kernel@...r.kernel.org
> Cc: grant.jung@...sung.com; jt77.jang@...sung.com;
> dh0421.hwang@...sung.com; junwoo80.lee@...sung.com; jangsub.yi@...sung.com;
> cw9316.lee@...sung.com; sh8267.baek@...sung.com; wkon.kim@...sung.com;
> Seunghui Lee <sh043.lee@...sung.com>
> Subject: [PATCH] scsi: ufs: no sw reset after last linkstartup fail
> 
> Host driver resets the host(ufshcd_hba_enable) after last linkstartup
> command failed. All of the member or host dump after linkstartup fail are
> reset value because of sw reset.
> 
> Signed-off-by: Junwoo Lee <junwoo80.lee@...sung.com>
> Signed-off-by: Seunghui Lee <sh043.lee@...sung.com>
> ---
>  drivers/ufs/core/ufshcd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c index
> 7c1d7bb9c579..2cdc14675443 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -4753,7 +4753,7 @@ static int ufshcd_link_startup(struct ufs_hba *hba)
>  		 * but we can't be sure if the link is up until link startup
>  		 * succeeds. So reset the local Uni-Pro and try again.
>  		 */
> -		if (ret && ufshcd_hba_enable(hba)) {
> +		if (ret && retries && ufshcd_hba_enable(hba)) {
>  			ufshcd_update_evt_hist(hba,
>  					       UFS_EVT_LINK_STARTUP_FAIL,
>  					       (u32)ret);
> --
> 2.29.0