linux-kernel - Re: [PATCH v3 1/2] scsi: ufs: core: check asymmetric connected lanes

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Message-ID: <52ed0795-c493-414c-b22b-86c90b8d89c8@acm.org>
Date: Tue, 15 Oct 2024 11:16:39 -0700
From: Bart Van Assche <bvanassche@....org>
To: SEO HOYOUNG <hy50.seo@...sung.com>, linux-scsi@...r.kernel.org,
 linux-kernel@...r.kernel.org, alim.akhtar@...sung.com, avri.altman@....com,
 jejb@...ux.ibm.com, martin.petersen@...cle.com, beanhuo@...ron.com,
 kwangwon.min@...sung.com, kwmad.kim@...sung.com, sh425.lee@...sung.com,
 quic_nguyenb@...cinc.com, cpgs@...sung.com, h10.kim@...sung.com,
 grant.jung@...sung.com, junwoo80.lee@...sung.com, wkon.kim@...sung.com
Subject: Re: [PATCH v3 1/2] scsi: ufs: core: check asymmetric connected lanes

On 10/10/24 12:52 AM, SEO HOYOUNG wrote:
> Performance problems may occur if there is a problem with the
> asymmetric connected lane such as h/w failure.
> Currently, only check connected lane for rx/tx is checked if it is not 0.
> But it should also be checked if it is asymmetrically connected.
> 
> Signed-off-by: SEO HOYOUNG <hy50.seo@...sung.com>
> ---
>   drivers/ufs/core/ufshcd.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 24a32e2fd75e..387eec6f19ef 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -4540,6 +4540,14 @@ static int ufshcd_get_max_pwr_mode(struct ufs_hba *hba)
>   		return -EINVAL;
>   	}
>   
> +	if (pwr_info->lane_rx != pwr_info->lane_tx) {
> +		dev_err(hba->dev, "%s: asymmetric connected lanes. rx=%d, tx=%d\n",
> +			__func__,
> +				pwr_info->lane_rx,
> +				pwr_info->lane_tx);
> +		return -EINVAL;
> +	}
> +
>   	/*
>   	 * First, get the maximum gears of HS speed.
>   	 * If a zero value, it means there is no HSGEAR capability.

It seems to me that symmetry of the number of lanes is required by the
UFS standard? From the UFS standard: "An equal number of downstream and
upstream lanes shall be provided in each link." Hence:

Reviewed-by: Bart Van Assche <bvanassche@....org>