[PATCH 1/2] drm/tidss: Clear the interrupt status for interrupts being disabled

[Devarsh Thakkar]

It is possible that dispc_{k2g/k3}_set_irqenable can be called for
disabling some interrupt events which were previously enabled. However
instead of clearing any pending events for the interrupt events that are
required to be disabled, it was instead clearing the new interrupt events
which were not even enabled. 

For e.g. While disabling the vsync events, dispc_k3_set_irqenable tries to
clear DSS_IRQ_DEVICE_OCP_ERR which was not enabled per the old_mask at all
as shown below :

"dispc_k3_set_irqenable : irqenabled - mask = 91, old = f0, clr = 1" where
clr = (mask ^ old_mask) & old_mask

This corrects the bit mask to make sure that it always clears any pending
interrupt events that are requested to be disabled before disabling them
actually.

Fixes: 32a1795f57ee ("drm/tidss: New driver for TI Keystone platform Display SubSystem")
Reported-by: Jonathan Cormier <jcormier at criticallink.com>
Signed-off-by: Devarsh Thakkar <devarsht at ti.com>
---
 drivers/gpu/drm/tidss/tidss_dispc.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/tidss/tidss_dispc.c b/drivers/gpu/drm/tidss/tidss_dispc.c
index 1ad711f8d2a8..b04419b24863 100644
--- a/drivers/gpu/drm/tidss/tidss_dispc.c
+++ b/drivers/gpu/drm/tidss/tidss_dispc.c
@@ -700,8 +700,8 @@ 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 */
-	dispc_k2g_clear_irqstatus(dispc, (mask ^ old_mask) & mask);
+	/* clear the irqstatus for irqs that are being disabled now */
+	dispc_k2g_clear_irqstatus(dispc, (mask ^ old_mask) & old_mask);
 
 	dispc_k2g_vp_set_irqenable(dispc, 0, mask);
 	dispc_k2g_vid_set_irqenable(dispc, 0, mask);
@@ -843,8 +843,8 @@ static void dispc_k3_set_irqenable(struct dispc_device *dispc,
 
 	old_mask = dispc_k3_read_irqenable(dispc);
 
-	/* clear the irqstatus for newly enabled irqs */
-	dispc_k3_clear_irqstatus(dispc, (old_mask ^ mask) & mask);
+	/* clear the irqstatus for irqs that are being disabled now */
+	dispc_k3_clear_irqstatus(dispc, (old_mask ^ mask) & old_mask);
 
 	for (i = 0; i < dispc->feat->num_vps; ++i) {
 		dispc_k3_vp_set_irqenable(dispc, i, mask);
-- 
2.39.1