[Intel-gfx] [PATCH] drm/i915: BXT DDI PHY sequence BUN

[Jani Nikula]

On Mon, 21 Mar 2016, Vandana Kannan <vandana.kannan at intel.com> wrote:
> According to the BSpec update, bit 7 of PORT_CL1CM_DW0 register needs to be
> checked to ensure that the register is in accessible state.

*sigh* the bspec is still not updated, and I didn't get the BUN.

> Also, based on a BSpec update, changing the timeout value to
> check iphypwrgood, from 10ms to wait for up to 100us.
>
> Signed-off-by: Vandana Kannan <vandana.kannan at intel.com>
> Reported-by: Philippe Lecluse <Philippe.Lecluse at intel.com>
> Cc: Deak, Imre <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h  |  1 +
>  drivers/gpu/drm/i915/intel_ddi.c | 11 +++++++++--
>  2 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 7dfc400..9a02bfc 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -1318,6 +1318,7 @@ enum skl_disp_power_wells {
>  #define _PORT_CL1CM_DW0_A		0x162000
>  #define _PORT_CL1CM_DW0_BC		0x6C000
>  #define   PHY_POWER_GOOD		(1 << 16)
> +#define   PHY_RESERVED			(1 << 7)
>  #define BXT_PORT_CL1CM_DW0(phy)		_BXT_PHY((phy), _PORT_CL1CM_DW0_BC, \
>  							_PORT_CL1CM_DW0_A)
>  
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index 62de9f4..354f949 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -2669,9 +2669,16 @@ static void broxton_phy_init(struct drm_i915_private *dev_priv,
>  	val |= GT_DISPLAY_POWER_ON(phy);
>  	I915_WRITE(BXT_P_CR_GT_DISP_PWRON, val);
>  
> -	/* Considering 10ms timeout until BSpec is updated */
> -	if (wait_for(I915_READ(BXT_PORT_CL1CM_DW0(phy)) & PHY_POWER_GOOD, 10))
> +	/*
> +	 * HW team confirmed that the time to reach phypowergood status is
> +	 * anywhere between 50 us and 100us.
> +	 */
> +	if (wait_for_atomic_us(((!(I915_READ(BXT_PORT_CL1CM_DW0(phy)) &
> +				PHY_RESERVED)) &&
> +				((I915_READ(BXT_PORT_CL1CM_DW0(phy)) &
> +				  PHY_POWER_GOOD) == PHY_POWER_GOOD)), 100)) {

Is there any reason why you'd need to do the read twice? Why not just
write it as:

(I915_READ(BXT_PORT_CL1CM_DW0(phy)) & (PHY_RESERVED | PHY_POWER_GOOD)) == PHY_POWER_GOOD

BR,
Jani.

>  		DRM_ERROR("timeout during PHY%d power on\n", phy);
> +	}
>  
>  	for (port =  (phy == DPIO_PHY0 ? PORT_B : PORT_A);
>  	     port <= (phy == DPIO_PHY0 ? PORT_C : PORT_A); port++) {

-- 
Jani Nikula, Intel Open Source Technology Center