[4/4] scsi: ufs: core: Use reg_lock to protect HCE register

Use the host register lock to serialize access to the Host Controller
Enable (HCE) register as well, instead of the host_lock.

Signed-off-by: Avri Altman <avri.altman@wdc.com>
---
 drivers/ufs/core/ufshcd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

On 10/21/24 5:03 AM, Avri Altman wrote:
> Use the host register lock to serialize access to the Host Controller
> Enable (HCE) register as well, instead of the host_lock.
> 
> Signed-off-by: Avri Altman <avri.altman@wdc.com>
> ---
>   drivers/ufs/core/ufshcd.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> index 4eee737a4fd5..3cc8ffc6929f 100644
> --- a/drivers/ufs/core/ufshcd.c
> +++ b/drivers/ufs/core/ufshcd.c
> @@ -4795,9 +4795,9 @@ void ufshcd_hba_stop(struct ufs_hba *hba)
>   	 * Obtain the host lock to prevent that the controller is disabled
>   	 * while the UFS interrupt handler is active on another CPU.
>   	 */
> -	spin_lock_irqsave(hba->host->host_lock, flags);
> +	spin_lock_irqsave(&hba->reg_lock, flags);
>   	ufshcd_writel(hba, CONTROLLER_DISABLE,  REG_CONTROLLER_ENABLE);
> -	spin_unlock_irqrestore(hba->host->host_lock, flags);
> +	spin_unlock_irqrestore(&hba->reg_lock, flags);
>   
>   	err = ufshcd_wait_for_register(hba, REG_CONTROLLER_ENABLE,
>   					CONTROLLER_ENABLE, CONTROLLER_DISABLE,

Hi Avri,

How about proceeding as follows for ufshcd_hba_stop():
* Remove the comment above the ufshcd_writel() call and add a
   disable_irq() call instead.
* Call enable_irq() after ufshcd_writel() has finished and before
   ufshcd_wait_for_register() is called.
* Do not hold any lock around the ufshcd_writel() call.

Although the legacy interrupt is disabled by some but not all
ufshcd_hba_stop() callers, I think it is safe to nest disable_irq()
calls. From kernel/irq/manage.c:

void __disable_irq(struct irq_desc *desc)
{
	if (!desc->depth++)
		irq_disable(desc);
}

Thanks,

Bart.

> On 10/21/24 5:03 AM, Avri Altman wrote:
> > Use the host register lock to serialize access to the Host Controller
> > Enable (HCE) register as well, instead of the host_lock.
> >
> > Signed-off-by: Avri Altman <avri.altman@wdc.com>
> > ---
> >   drivers/ufs/core/ufshcd.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> > index 4eee737a4fd5..3cc8ffc6929f 100644
> > --- a/drivers/ufs/core/ufshcd.c
> > +++ b/drivers/ufs/core/ufshcd.c
> > @@ -4795,9 +4795,9 @@ void ufshcd_hba_stop(struct ufs_hba *hba)
> >        * Obtain the host lock to prevent that the controller is disabled
> >        * while the UFS interrupt handler is active on another CPU.
> >        */
> > -     spin_lock_irqsave(hba->host->host_lock, flags);
> > +     spin_lock_irqsave(&hba->reg_lock, flags);
> >       ufshcd_writel(hba, CONTROLLER_DISABLE,  REG_CONTROLLER_ENABLE);
> > -     spin_unlock_irqrestore(hba->host->host_lock, flags);
> > +     spin_unlock_irqrestore(&hba->reg_lock, flags);
> >
> >       err = ufshcd_wait_for_register(hba, REG_CONTROLLER_ENABLE,
> >                                       CONTROLLER_ENABLE,
> > CONTROLLER_DISABLE,
> 
> Hi Avri,
> 
> How about proceeding as follows for ufshcd_hba_stop():
> * Remove the comment above the ufshcd_writel() call and add a
>    disable_irq() call instead.
> * Call enable_irq() after ufshcd_writel() has finished and before
>    ufshcd_wait_for_register() is called.
> * Do not hold any lock around the ufshcd_writel() call.
> 
> Although the legacy interrupt is disabled by some but not all
> ufshcd_hba_stop() callers, I think it is safe to nest disable_irq() calls. From
> kernel/irq/manage.c:
> 
> void __disable_irq(struct irq_desc *desc) {
>         if (!desc->depth++)
>                 irq_disable(desc);
> }
Thanks. I think I'll exclude this one from this series.
I want it to be clear that all instances are about removing redundant host_lock calls before register access.
Here, it’s a bit different since need to verify that the UFS interrupt handler is not active on another CPU.
I will follow your suggestion - but in another series.

Thanks,
Avri
> 
> Thanks,
> 
> Bart.