linux-kernel - Re: [PATCH v4 2/3] scsi: ufs: core: Introduce a new clock

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Message-ID: <2955aa00-824d-4803-96f6-35575ae9560e@acm.org>
Date: Thu, 21 Nov 2024 12:44:23 -0800
From: Bart Van Assche <bvanassche@....org>
To: Avri Altman <avri.altman@....com>,
 "Martin K . Petersen" <martin.petersen@...cle.com>
Cc: linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
 Bean Huo <beanhuo@...ron.com>
Subject: Re: [PATCH v4 2/3] scsi: ufs: core: Introduce a new clock_gating lock

On 11/18/24 6:41 AM, Avri Altman wrote:
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index be5fe2407382..638d9c0e2603 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -1816,19 +1816,17 @@ static void ufshcd_exit_clk_scaling(struct ufs_hba *hba)
>   static void ufshcd_ungate_work(struct work_struct *work)
>   {
>   	int ret;
> -	unsigned long flags;
>   	struct ufs_hba *hba = container_of(work, struct ufs_hba,
>   			clk_gating.ungate_work);
>   
>   	cancel_delayed_work_sync(&hba->clk_gating.gate_work);
>   
> -	spin_lock_irqsave(hba->host->host_lock, flags);
> -	if (hba->clk_gating.state == CLKS_ON) {
> -		spin_unlock_irqrestore(hba->host->host_lock, flags);
> -		return;
> +	scoped_guard(spinlock_irqsave, &hba->clk_gating.lock)
> +	{
> +		if (hba->clk_gating.state == CLKS_ON)
> +			return;
>   	}

Here and elsewhere, please move "{" to the end of the "scoped_guard()"
line since that is the style used in all other Linux kernel code (I know
that clang-format gets this wrong).

>   /* host lock must be held before calling this variant */

Please remove this comment since your patch makes it incorrect and
replace it with a lockdep_assert_held() call.

> +	spin_lock_irqsave(hba->host->host_lock, flags);
> +	if (ufshcd_has_pending_tasks(hba) ||
> +	    hba->ufshcd_state != UFSHCD_STATE_OPERATIONAL) {
> +		spin_unlock_irqrestore(hba->host->host_lock, flags);
> +		return;
> +	}
> +	spin_unlock_irqrestore(hba->host->host_lock, flags);

Why explicit lock/unlock calls instead of using scoped_guard()?

> diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
> index d7aca9e61684..8f9997b0dbf9 100644
> --- a/include/ufs/ufshcd.h
> +++ b/include/ufs/ufshcd.h
> @@ -403,6 +403,8 @@ enum clk_gating_state {
>    * delay_ms
>    * @ungate_work: worker to turn on clocks that will be used in case of
>    * interrupt context
> + * @clk_gating_workq: workqueue for clock gating work.
> + * @lock: serialize access to some struct ufs_clk_gating members

Please document that @lock is the outer lock relative to the host lock.

Thanks,

Bart.