[PATCH 6/8] drm: atmel-hlcdc: add XLCDC clock bypass support for small dividers

[Manikandan Muralidharan]

Define ATMEL_XLCDC_CLKBYP and set the clock bypass bit on XLCDC
hardware when the computed divider is less than 2, avoiding an
invalid divider value. Non-XLCDC hardware retains the existing
minimum divider clamp of 2.

Signed-off-by: Manikandan Muralidharan <manikandan.m at microchip.com>
---
 drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c | 7 +++++++
 include/linux/mfd/atmel-hlcdc.h                | 1 +
 2 files changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
index 6da428361c19..f837684654ea 100644
--- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
+++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
@@ -87,6 +87,13 @@ static int atmel_hlcdc_crtc_setup_clock(struct atmel_hlcdc_crtc *crtc,
 
 	div = DIV_ROUND_CLOSEST(prate, mode_rate);
 	if (div < 2) {
+		/* XLCDC: bypass divider when div < 2 */
+		if (crtc->dc->desc->is_xlcdc) {
+			*cfg  |= ATMEL_XLCDC_CLKBYP;
+			*mask |= ATMEL_XLCDC_CLKBYP;
+			return 0;
+		}
+		/* Enforce minimum divider for non-XLCDC */
 		div = 2;
 	} else if (ATMEL_HLCDC_CLKDIV(div) & ~ATMEL_HLCDC_CLKDIV_MASK) {
 		/* The divider ended up too big, try a lower base rate. */
diff --git a/include/linux/mfd/atmel-hlcdc.h b/include/linux/mfd/atmel-hlcdc.h
index 8e86219293b7..1463c7db0e64 100644
--- a/include/linux/mfd/atmel-hlcdc.h
+++ b/include/linux/mfd/atmel-hlcdc.h
@@ -44,6 +44,7 @@
 #define ATMEL_XLCDC_HEO_UPDATE		BIT(3)
 
 #define ATMEL_HLCDC_CLKPOL		BIT(0)
+#define ATMEL_XLCDC_CLKBYP		BIT(1)
 #define ATMEL_HLCDC_CLKSEL		BIT(2)
 #define ATMEL_HLCDC_CLKPWMSEL		BIT(3)
 #define ATMEL_HLCDC_CGDIS(i)		BIT(8 + (i))
-- 
2.25.1