From: Manikandan Muralidharan <manikandan.m@microchip•com>
To: <maarten.lankhorst@linux•intel.com>, <mripard@kernel•org>,
<tzimmermann@suse•de>, <airlied@gmail•com>, <simona@ffwll•ch>,
<nicolas.ferre@microchip•com>, <alexandre.belloni@bootlin•com>,
<claudiu.beznea@tuxon•dev>, <lee@kernel•org>,
<dri-devel@lists•freedesktop.org>,
<linux-arm-kernel@lists•infradead.org>,
<linux-kernel@vger•kernel.org>
Cc: <manikandan.m@microchip•com>
Subject: [PATCH 6/8] drm: atmel-hlcdc: add XLCDC clock bypass support for small dividers
Date: Tue, 19 May 2026 14:31:33 +0530 [thread overview]
Message-ID: <20260519090135.1188405-7-manikandan.m@microchip.com> (raw)
In-Reply-To: <20260519090135.1188405-1-manikandan.m@microchip.com>
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@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
next prev parent reply other threads:[~2026-05-19 9:02 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-19 9:01 [PATCH 0/8] drm: atmel-hlcdc: fix clock handling and add LVDS support Manikandan Muralidharan
2026-05-19 9:01 ` [PATCH 1/8] drm: atmel-hlcdc: Fix off-by-one in vertical back porch setting Manikandan Muralidharan
2026-05-19 9:01 ` [PATCH 2/8] drm: atmel-hlcdc: reorder timing register writes after clock setup Manikandan Muralidharan
2026-05-19 9:01 ` [PATCH 3/8] drm: atmel-hlcdc: simplify clock divider selection with DIV_ROUND_CLOSEST Manikandan Muralidharan
2026-05-19 9:01 ` [PATCH 4/8] drm: atmel-hlcdc: define ATMEL_HLCDC_CLKDIV_MAX and fix divider fallback Manikandan Muralidharan
2026-05-19 9:01 ` [PATCH 5/8] drm: atmel-hlcdc: extract clock setup into a dedicated helper Manikandan Muralidharan
2026-05-19 9:01 ` Manikandan Muralidharan [this message]
2026-05-27 14:55 ` [PATCH 6/8] drm: atmel-hlcdc: add XLCDC clock bypass support for small dividers Lee Jones
2026-05-19 9:01 ` [PATCH 7/8] drm: atmel-hlcdc: add and configure LVDS PLL clock support Manikandan Muralidharan
2026-05-19 9:01 ` [PATCH 8/8] drm: atmel-hlcdc: add LVDS output mode support Manikandan Muralidharan
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