[PATCH 4/8] drm: atmel-hlcdc: define ATMEL_HLCDC_CLKDIV_MAX and fix divider fallback

[Manikandan Muralidharan <manikandan.m@microchip.com>]

Introduce ATMEL_HLCDC_CLKDIV_MAX to replace the raw mask.In the divider
overflow fallback, restrict the clock source switch and halved rate
retry to SoCs that support the 2x system clock path.

Signed-off-by: Manikandan Muralidharan <manikandan.m@microchip.com>
---
 drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c | 9 +++++----
 include/linux/mfd/atmel-hlcdc.h                | 1 +
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
index f30138da1ed8..c7e77bb2941a 100644
--- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
+++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
@@ -117,11 +117,12 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c)
 		div = 2;
 	} else if (ATMEL_HLCDC_CLKDIV(div) & ~ATMEL_HLCDC_CLKDIV_MASK) {
 		/* The divider ended up too big, try a lower base rate. */
-		cfg &= ~ATMEL_HLCDC_CLKSEL;
-		prate /= 2;
-		div = DIV_ROUND_CLOSEST(prate, mode_rate);
+		if (!crtc->dc->desc->fixed_clksrc) {
+			cfg &= ~ATMEL_HLCDC_CLKSEL;
+			div = DIV_ROUND_CLOSEST(prate >> 1, mode_rate);
+		}
 		if (ATMEL_HLCDC_CLKDIV(div) & ~ATMEL_HLCDC_CLKDIV_MASK)
-			div = ATMEL_HLCDC_CLKDIV_MASK;
+			div = ATMEL_HLCDC_CLKDIV_MAX;
 	}
 
 	cfg |= ATMEL_HLCDC_CLKDIV(div);
diff --git a/include/linux/mfd/atmel-hlcdc.h b/include/linux/mfd/atmel-hlcdc.h
index 07c2081867fd..8e86219293b7 100644
--- a/include/linux/mfd/atmel-hlcdc.h
+++ b/include/linux/mfd/atmel-hlcdc.h
@@ -50,6 +50,7 @@
 #define ATMEL_HLCDC_CLKDIV_SHFT		16
 #define ATMEL_HLCDC_CLKDIV_MASK		GENMASK(23, 16)
 #define ATMEL_HLCDC_CLKDIV(div)		((div - 2) << ATMEL_HLCDC_CLKDIV_SHFT)
+#define ATMEL_HLCDC_CLKDIV_MAX		((ATMEL_HLCDC_CLKDIV_MASK >> ATMEL_HLCDC_CLKDIV_SHFT) + 2)
 
 #define ATMEL_HLCDC_PIXEL_CLK		BIT(0)
 #define ATMEL_HLCDC_SYNC		BIT(1)
-- 
2.25.1