linux-kernel - Re: [PATCH v1 7/9] scsi: ufs: add UFS power collapse support during hibern8

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Date:   Fri, 20 Jul 2018 16:58:09 -0700
From:   Subhash Jadavani <subhashj@...eaurora.org>
To:     Asutosh Das <asutoshd@...eaurora.org>
Cc:     cang@...eaurora.org, vivek.gautam@...eaurora.org,
        rnayak@...eaurora.org, vinholikatti@...il.com,
        jejb@...ux.vnet.ibm.com, martin.petersen@...cle.com,
        linux-scsi@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Venkat Gopalakrishnan <venkatg@...eaurora.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 7/9] scsi: ufs: add UFS power collapse support during
 hibern8

On 2018-07-06 05:30, Asutosh Das wrote:
> From: Subhash Jadavani <subhashj@...eaurora.org>
> 
> UFS host controller hardware may allow the host controller
> to be power collapsed when UFS link is hibern8 state, this
> change allows the UFS host controller to be power collapsed
> during hibern8.
> 
> Signed-off-by: Subhash Jadavani <subhashj@...eaurora.org>
> Signed-off-by: Venkat Gopalakrishnan <venkatg@...eaurora.org>
> Signed-off-by: Can Guo <cang@...eaurora.org>
> Signed-off-by: Asutosh Das <asutoshd@...eaurora.org>
> ---
>  drivers/scsi/ufs/ufshcd.c |  8 ++++++--
>  drivers/scsi/ufs/ufshcd.h | 13 ++++++++++++-
>  2 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> index 40d9c35..50588cf 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -7673,13 +7673,17 @@ static int ufshcd_vreg_set_hpm(struct ufs_hba 
> *hba)
> 
>  static void ufshcd_hba_vreg_set_lpm(struct ufs_hba *hba)
>  {
> -	if (ufshcd_is_link_off(hba))
> +	if (ufshcd_is_link_off(hba) ||
> +	    (ufshcd_is_link_hibern8(hba)
> +	     && ufshcd_is_power_collapse_during_hibern8_allowed(hba)))
>  		ufshcd_setup_hba_vreg(hba, false);

I guess we have to handle the UFS host controller power collapse via 
"power-domains" which would requires us to specify the "power-domains" 
attribute under UFS controller's DT node and then linux core power 
framework should automatically collapse the UFS controller post runtime 
suspend. This also means we can't power collapse UFS controller 
aggressively (as part of clock gating) but it should still be fine from 
power point of view.

>  }
> 
>  static void ufshcd_hba_vreg_set_hpm(struct ufs_hba *hba)
>  {
> -	if (ufshcd_is_link_off(hba))
> +	if (ufshcd_is_link_off(hba) ||
> +	    (ufshcd_is_link_hibern8(hba)
> +	     && ufshcd_is_power_collapse_during_hibern8_allowed(hba)))
>  		ufshcd_setup_hba_vreg(hba, true);
>  }
> 
> diff --git a/drivers/scsi/ufs/ufshcd.h b/drivers/scsi/ufs/ufshcd.h
> index f79a639..8c5f987 100644
> --- a/drivers/scsi/ufs/ufshcd.h
> +++ b/drivers/scsi/ufs/ufshcd.h
> @@ -728,7 +728,12 @@ struct ufs_hba {
>  	 * to do background operation when it's active but it might degrade
>  	 * the performance of ongoing read/write operations.
>  	 */
> -#define UFSHCD_CAP_KEEP_AUTO_BKOPS_ENABLED_EXCEPT_SUSPEND (1 << 5)
> +#define UFSHCD_CAP_KEEP_AUTO_BKOPS_ENABLED_EXCEPT_SUSPEND (1 << 6)
> +	/*
> +	 * If host controller hardware can be power collapsed when UFS link 
> is
> +	 * in hibern8 then enable this cap.
> +	 */
> +#define UFSHCD_CAP_POWER_COLLAPSE_DURING_HIBERN8 (1 << 7)
> 
>  	struct devfreq *devfreq;
>  	struct ufs_clk_scaling clk_scaling;
> @@ -764,6 +769,12 @@ static inline bool
> ufshcd_is_hibern8_on_idle_allowed(struct ufs_hba *hba)
>  	return hba->caps & UFSHCD_CAP_HIBERN8_ENTER_ON_IDLE;
>  }
> 
> +static inline bool ufshcd_is_power_collapse_during_hibern8_allowed(
> +						struct ufs_hba *hba)
> +{
> +	return !!(hba->caps & UFSHCD_CAP_POWER_COLLAPSE_DURING_HIBERN8);
> +}
> +
>  static inline bool ufshcd_is_intr_aggr_allowed(struct ufs_hba *hba)
>  {
>  /* DWC UFS Core has the Interrupt aggregation feature but is not 
> detectable*/

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