[Intel-gfx] [PATCH] drm/i915/cnl: Mask previous DDI - PLL mapping

[Rodrigo Vivi]

On Fri, Dec 01, 2017 at 02:17:00AM +0000, James Ausmus wrote:
> Without masking out the old value, we can end up pointing the DDI to a
> disabled PLL, which makes the system fall over. Mask out the previous
> value before setting the PLL to DDI mapping.
> 
> This can be observed by running igt/testdisplay with both an eDP and
> HDMI/DP output active.
> 
> v2: Add the Bugzilla link
> 
> Fixes: 555e38d273172 ("drm/i915/cnl: DDI - PLL mapping")
> Testcase: igt/testdisplay
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103997
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: Matt Atwood <matthew.s.atwood at intel.com>
> Signed-off-by: James Ausmus <james.ausmus at intel.com>


Reviewed-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
Tested-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
Bug-introduced-by: Rodrigo Vivi <rodrigo.vivi at intel.com> :)

Thanks a lot for the patch! merging asap...

> ---
>  drivers/gpu/drm/i915/intel_ddi.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index eff3b51872eb..123a3253453f 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -2098,6 +2098,7 @@ static void intel_ddi_clk_select(struct intel_encoder *encoder,
>  	if (IS_CANNONLAKE(dev_priv)) {
>  		/* Configure DPCLKA_CFGCR0 to map the DPLL to the DDI. */
>  		val = I915_READ(DPCLKA_CFGCR0);
> +		val &= ~DPCLKA_CFGCR0_DDI_CLK_SEL_MASK(port);
>  		val |= DPCLKA_CFGCR0_DDI_CLK_SEL(pll->id, port);
>  		I915_WRITE(DPCLKA_CFGCR0, val);
>  
> -- 
> 2.15.1
>