linux-kernel - Re: [PATCH v2 2/2] scsi: ufs: core: Replace hard coded vcc-off delay with a variable

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Message-ID: <714110b991f9ced2c8d496afc767d8666ad8332a.camel@mediatek.com>
Date: Mon, 13 Oct 2025 03:58:32 +0000
From: Peter Wang (王信友) <peter.wang@...iatek.com>
To: "quic_cang@...cinc.com" <quic_cang@...cinc.com>,
	"martin.petersen@...cle.com" <martin.petersen@...cle.com>,
	"adrian.hunter@...el.com" <adrian.hunter@...el.com>, "bvanassche@....org"
	<bvanassche@....org>, "quic_nguyenb@...cinc.com" <quic_nguyenb@...cinc.com>,
	"quic_nitirawa@...cinc.com" <quic_nitirawa@...cinc.com>,
	"avri.altman@....com" <avri.altman@....com>
CC: "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
	"beanhuo@...ron.com" <beanhuo@...ron.com>, "neil.armstrong@...aro.org"
	<neil.armstrong@...aro.org>, "alim.akhtar@...sung.com"
	<alim.akhtar@...sung.com>, "James.Bottomley@...senPartnership.com"
	<James.Bottomley@...senPartnership.com>, "ebiggers@...nel.org"
	<ebiggers@...nel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] scsi: ufs: core: Replace hard coded vcc-off delay
 with a variable

On Thu, 2025-10-09 at 13:10 -0700, Bao D. Nguyen wrote:
> 
> +       /*
> +        * Most ufs devices require 1ms delay after vcc is powered
> off before
> +        * it can be powered on again. Set the default to 5ms. The
> platform
> +        * drivers can override this setting as needed.
> +        */
> +       hba->sleep_post_vcc_off = 5000;
> +
> 

Hi Bao,

Since 2ms is sufficient for most devices, wouldn't it make
sense to set the default value to 2ms?


>         init_completion(&hba->dev_cmd.complete);
> 
>         err = ufshcd_hba_init(hba);
> diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
> index 1d39437..ad49979 100644
> --- a/include/ufs/ufshcd.h
> +++ b/include/ufs/ufshcd.h
> @@ -1140,6 +1140,8 @@ struct ufs_hba {
>         int critical_health_count;
>         atomic_t dev_lvl_exception_count;
>         u64 dev_lvl_exception_id;
> +
> +       u32 sleep_post_vcc_off;
> 

The name sleep_post_vcc_off might be misunderstood as a 
status or a flag. I suggest changing it to a more explicit 
name, such as vcc_off_delay_ms.


Thanks
Peter