drm/bridge: cdns-mhdp8546: Fix the interrupt enable/disable

When removing the tidss driver, there is a warning reported by
kernel about an unhandled interrupt for mhdp driver.

[   43.238895] irq 31: nobody cared (try booting with the "irqpoll" option)
... [snipped backtrace]
[   43.330735] handlers:
[   43.333020] [<000000005367c4f9>] irq_default_primary_handler threaded [<000000007e02b601>]
cdns_mhdp_irq_handler [cdns_mhdp8546]
[   43.344607] Disabling IRQ #31

This happens because as part of cdns_mhdp_bridge_hpd_disable, driver tries
to disable the interrupts. While disabling the SW_EVENT interrupts,
it accidentally enables the MBOX interrupts, which are not handled by
the driver.

Fix this with a read-modify-write to update only required bits.
Use the enable / disable function as required in other places.
Signed-off-by: Nikhil Devshatwar <nikhil.nd@ti.com>
Reviewed-by: Swapnil Jakhade <sjakhade@cadence.com>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Aradhya Bhatia <a-bhatia1@ti.com>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230606082142.23760-9-a-bhatia1@ti.com

drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c

@@ -54,6 +54,26 @@
 #include "cdns-mhdp8546-hdcp.h"
 #include "cdns-mhdp8546-j721e.h"
 
+static void cdns_mhdp_bridge_hpd_enable(struct drm_bridge *bridge)
+{
+	struct cdns_mhdp_device *mhdp = bridge_to_mhdp(bridge);
+
+	/* Enable SW event interrupts */
+	if (mhdp->bridge_attached)
+		writel(readl(mhdp->regs + CDNS_APB_INT_MASK) &
+		       ~CDNS_APB_INT_MASK_SW_EVENT_INT,
+		       mhdp->regs + CDNS_APB_INT_MASK);
+}
+
+static void cdns_mhdp_bridge_hpd_disable(struct drm_bridge *bridge)
+{
+	struct cdns_mhdp_device *mhdp = bridge_to_mhdp(bridge);
+
+	writel(readl(mhdp->regs + CDNS_APB_INT_MASK) |
+	       CDNS_APB_INT_MASK_SW_EVENT_INT,
+	       mhdp->regs + CDNS_APB_INT_MASK);
+}
+
 static int cdns_mhdp_mailbox_read(struct cdns_mhdp_device *mhdp)
 {
 	int ret, empty;
@@ -749,9 +769,7 @@ static int cdns_mhdp_fw_activate(const struct firmware *fw,
 	 * MHDP_HW_STOPPED happens only due to driver removal when
 	 * bridge should already be detached.
 	 */
-	if (mhdp->bridge_attached)
-		writel(~(u32)CDNS_APB_INT_MASK_SW_EVENT_INT,
-		       mhdp->regs + CDNS_APB_INT_MASK);
+	cdns_mhdp_bridge_hpd_enable(&mhdp->bridge);
 
 	spin_unlock(&mhdp->start_lock);
 
@@ -1740,8 +1758,7 @@ static int cdns_mhdp_attach(struct drm_bridge *bridge,
 
 	/* Enable SW event interrupts */
 	if (hw_ready)
-		writel(~(u32)CDNS_APB_INT_MASK_SW_EVENT_INT,
-		       mhdp->regs + CDNS_APB_INT_MASK);
+		cdns_mhdp_bridge_hpd_enable(bridge);
 
 	return 0;
 aux_unregister:
@@ -2212,23 +2229,6 @@ static struct edid *cdns_mhdp_bridge_get_edid(struct drm_bridge *bridge,
 	return cdns_mhdp_get_edid(mhdp, connector);
 }
 
-static void cdns_mhdp_bridge_hpd_enable(struct drm_bridge *bridge)
-{
-	struct cdns_mhdp_device *mhdp = bridge_to_mhdp(bridge);
-
-	/* Enable SW event interrupts */
-	if (mhdp->bridge_attached)
-		writel(~(u32)CDNS_APB_INT_MASK_SW_EVENT_INT,
-		       mhdp->regs + CDNS_APB_INT_MASK);
-}
-
-static void cdns_mhdp_bridge_hpd_disable(struct drm_bridge *bridge)
-{
-	struct cdns_mhdp_device *mhdp = bridge_to_mhdp(bridge);
-
-	writel(CDNS_APB_INT_MASK_SW_EVENT_INT, mhdp->regs + CDNS_APB_INT_MASK);
-}
-
 static const struct drm_bridge_funcs cdns_mhdp_bridge_funcs = {
 	.atomic_enable = cdns_mhdp_atomic_enable,
 	.atomic_disable = cdns_mhdp_atomic_disable,