[PATCH v2 6/6] drm/bridge: cdns-mhdp8546: Fix the interrupt enable/disable

[Nikhil Devshatwar]

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.
Do the same for enabling interrupts as well.

Signed-off-by: Nikhil Devshatwar <nikhil.nd at ti.com>
---
 drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
index 2cd809eed827..6beccd2a408e 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-mhdp8546-core.c
@@ -2146,7 +2146,8 @@ static void cdns_mhdp_bridge_hpd_enable(struct drm_bridge *bridge)
 
 	/* Enable SW event interrupts */
 	if (mhdp->bridge_attached)
-		writel(~(u32)CDNS_APB_INT_MASK_SW_EVENT_INT,
+		writel(readl(mhdp->regs + CDNS_APB_INT_MASK) &
+		       ~CDNS_APB_INT_MASK_SW_EVENT_INT,
 		       mhdp->regs + CDNS_APB_INT_MASK);
 }
 
@@ -2154,7 +2155,9 @@ 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);
+	writel(readl(mhdp->regs + CDNS_APB_INT_MASK) |
+	       CDNS_APB_INT_MASK_SW_EVENT_INT,
+	       mhdp->regs + CDNS_APB_INT_MASK);
 }
 
 static const struct drm_bridge_funcs cdns_mhdp_bridge_funcs = {
-- 
2.17.1