drm/i915: Remove struct_mutex in i915_irq.c

Remove struct_mutex from ivb_parity_work() function.

The ivb_parity_work runs in a workqueue so it cannot race with itself.

Also, it is not protecting anything with the other remaining usage of
struct_mutex.

Signed-off-by: Luiz Otavio Mello <luiz.mello@estudante.ufscar.br>
Suggested-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://lore.kernel.org/r/20250908131518.36625-3-luiz.mello@estudante.ufscar.br
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Author: LuizOt31

drivers/gpu/drm/i915/i915_irq.c

@@ -163,11 +163,6 @@ static void ivb_parity_work(struct work_struct *work)
 	u32 misccpctl;
 	u8 slice = 0;
 
-	/* We must turn off DOP level clock gating to access the L3 registers.
-	 * In order to prevent a get/put style interface, acquire struct mutex
-	 * any time we access those registers.
-	 */
-	mutex_lock(&dev_priv->struct_mutex);
 
 	/* If we've screwed up tracking, just let the interrupt fire again */
 	if (drm_WARN_ON(&dev_priv->drm, !dev_priv->l3_parity.which_slice))
@@ -225,7 +220,6 @@ static void ivb_parity_work(struct work_struct *work)
 	gen5_gt_enable_irq(gt, GT_PARITY_ERROR(dev_priv));
 	spin_unlock_irq(gt->irq_lock);
 
-	mutex_unlock(&dev_priv->struct_mutex);
 }
 
 static irqreturn_t valleyview_irq_handler(int irq, void *arg)