drm/tidss: Clear the interrupt status for interrupts being disabled

The driver does not touch the irqstatus register when it is disabling
interrupts.  This might cause an interrupt to trigger for an interrupt
that was just disabled.

To fix the issue, clear the irqstatus registers right after disabling
the interrupts.

Fixes: 32a1795 ("drm/tidss: New driver for TI Keystone platform Display SubSystem")
Cc: stable@vger.kernel.org
Reported-by: Jonathan Cormier <jcormier@criticallink.com>
Closes: https://e2e.ti.com/support/processors-group/processors/f/processors-forum/1394222/am625-issue-about-tidss-rcu_preempt-self-detected-stall-on-cpu/5424479#5424479
Signed-off-by: Devarsh Thakkar <devarsht@ti.com>
[Tomi: mostly rewrote the patch]
Reviewed-by: Jonathan Cormier <jcormier@criticallink.com>
Tested-by: Jonathan Cormier <jcormier@criticallink.com>
Reviewed-by: Aradhya Bhatia <aradhya.bhatia@linux.dev>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241021-tidss-irq-fix-v1-5-82ddaec94e4a@ideasonboard.com

drivers/gpu/drm/tidss/tidss_dispc.c

@@ -700,14 +700,17 @@ void dispc_k2g_set_irqenable(struct dispc_device *dispc, dispc_irq_t mask)
 {
 	dispc_irq_t old_mask = dispc_k2g_read_irqenable(dispc);
 
-	/* clear the irqstatus for newly enabled irqs */
+	/* clear the irqstatus for irqs that will be enabled */
 	dispc_k2g_clear_irqstatus(dispc, (mask ^ old_mask) & mask);
 
 	dispc_k2g_vp_set_irqenable(dispc, 0, mask);
 	dispc_k2g_vid_set_irqenable(dispc, 0, mask);
 
 	dispc_write(dispc, DISPC_IRQENABLE_SET, (1 << 0) | (1 << 7));
 
+	/* clear the irqstatus for irqs that were disabled */
+	dispc_k2g_clear_irqstatus(dispc, (mask ^ old_mask) & old_mask);
+
 	/* flush posted write */
 	dispc_k2g_read_irqenable(dispc);
 }
@@ -837,7 +840,7 @@ static void dispc_k3_set_irqenable(struct dispc_device *dispc,
 
 	old_mask = dispc_k3_read_irqenable(dispc);
 
-	/* clear the irqstatus for newly enabled irqs */
+	/* clear the irqstatus for irqs that will be enabled */
 	dispc_k3_clear_irqstatus(dispc, (old_mask ^ mask) & mask);
 
 	for (i = 0; i < dispc->feat->num_vps; ++i) {
@@ -862,6 +865,9 @@ static void dispc_k3_set_irqenable(struct dispc_device *dispc,
 	if (main_disable)
 		dispc_write(dispc, DISPC_IRQENABLE_CLR, main_disable);
 
+	/* clear the irqstatus for irqs that were disabled */
+	dispc_k3_clear_irqstatus(dispc, (old_mask ^ mask) & old_mask);
+
 	/* Flush posted writes */
 	dispc_read(dispc, DISPC_IRQENABLE_SET);
 }