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

[Lee Jones]

On Tue, 19 May 2026, Manikandan Muralidharan wrote:

> 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 +

Acked-by: Lee Jones <lee at kernel.org>

>  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
> 

-- 
Lee Jones