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

[Andrzej Hajda]

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 <justo...@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.ha...@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)