Re: [Intel-gfx] [PATCH v3] drm/i915/pxp: don't start pxp without mei_pxp bind

[Andrzej Hajda <andrzej.hajda@intel.com>]

On 18.08.2022 19:42, Juston Li wrote:
> pxp will not start correctly until after mei_pxp bind completes and
> intel_pxp_init_hw() is called.
> Wait for the bind to complete before proceeding with startup.
> 
> This fixes a race condition during bootup where we observed a small
> window for pxp commands to be sent, starting pxp before mei_pxp bind
> completed.
> 
> Changes since v2:
> - wait for pxp_component to bind instead of returning -EAGAIN (Daniele)
> 
> Changes since v1:
> - check pxp_component instead of pxp_component_added (Daniele)
> - pxp_component needs tee_mutex (Daniele)
> - return -EAGAIN so caller knows to retry (Daniele)
> 
> Signed-off-by: Juston Li <justonli@chromium.org>

In typical usage of component framework driver postpones initialization 
till component is bound. In such case checking/waiting for component as 
in this patch is not necessary and the code is more straightforward.
I wonder how it behaves on component unbind.

Anyway:
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>

Regards
Andrzej


> ---
>   drivers/gpu/drm/i915/pxp/intel_pxp.c | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp.c b/drivers/gpu/drm/i915/pxp/intel_pxp.c
> index 15311eaed848..17109c513259 100644
> --- a/drivers/gpu/drm/i915/pxp/intel_pxp.c
> +++ b/drivers/gpu/drm/i915/pxp/intel_pxp.c
> @@ -176,6 +176,18 @@ static void pxp_queue_termination(struct intel_pxp *pxp)
>   	spin_unlock_irq(&gt->irq_lock);
>   }
>   
> +static bool pxp_component_bound(struct intel_pxp *pxp)
> +{
> +	bool bound = false;
> +
> +	mutex_lock(&pxp->tee_mutex);
> +	if (pxp->pxp_component)
> +		bound = true;
> +	mutex_unlock(&pxp->tee_mutex);
> +
> +	return bound;
> +}
> +
>   /*
>    * the arb session is restarted from the irq work when we receive the
>    * termination completion interrupt
> @@ -187,6 +199,9 @@ int intel_pxp_start(struct intel_pxp *pxp)
>   	if (!intel_pxp_is_enabled(pxp))
>   		return -ENODEV;
>   
> +	if (wait_for(pxp_component_bound(pxp), 250))
> +		return -ENXIO;
> +
>   	mutex_lock(&pxp->arb_mutex);
>   
>   	if (pxp->arb_is_valid)