Re: [PATCH v2] drm/i915/ehl: Allow combo PHY A to drive a third external display

Ville Syrjälä
2019-06-18T16:08:58Z

On Mon, Jun 17, 2019 at 04:48:10PM -0700, Matt Roper wrote:
> EHL has a mux on combo PHY A that allows it to be driven either by an
> internal display (DDI-A or DSI DPHY) or by an external display (DDI-D).
> This is a motherboard design decision that can not be changed on the
> fly. Unfortunately there are no strap registers that allow us to detect
> the board configuration directly, so let's use the VBT to try to figure
> it out and program the mux accordingly.
>
> v2:
> - Confirmed that VBT's dvo port refers to the DDI and not the PHY.
> Thus we can check more explicitly for (ddi_d && !(ddi_a || dsi)). If
> a bad VBT contradicts itself, let internal display win. (Ville)
>
> Cc: Clint Taylor <Clinton.A.Taylor@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> ---
> drivers/gpu/drm/i915/display/intel_bios.c | 3 ++
> .../gpu/drm/i915/display/intel_combo_phy.c | 36 +++++++++++++++++++
> drivers/gpu/drm/i915/i915_reg.h | 1 +
> 3 files changed, 40 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_bios.c b/drivers/gpu/drm/i915/display/intel_bios.c
> index c4710889cb32..0c9808132d67 100644
> --- a/drivers/gpu/drm/i915/display/intel_bios.c
> +++ b/drivers/gpu/drm/i915/display/intel_bios.c
> @@ -1668,6 +1668,9 @@ parse_general_definitions(struct drm_i915_private *dev_priv,
> if (!child->device_type)
> continue;
>
> + DRM_DEBUG_KMS("Found VBT child device with type 0x%x\n",
> + child->device_type);
> +

Was this hunk intentional?

> /*
> * Copy as much as we know (sizeof) and is available
> * (child_dev_size) of the child device. Accessing the data must
> diff --git a/drivers/gpu/drm/i915/display/intel_combo_phy.c b/drivers/gpu/drm/i915/display/intel_combo_phy.c
> index 841708da5a56..c18079a09a2e 100644
> --- a/drivers/gpu/drm/i915/display/intel_combo_phy.c
> +++ b/drivers/gpu/drm/i915/display/intel_combo_phy.c
> @@ -260,6 +260,32 @@ void intel_combo_phy_power_up_lanes(struct drm_i915_private *dev_priv,
> I915_WRITE(ICL_PORT_CL_DW10(port), val);
> }
>
> +static u32 ehl_combo_phy_a_mux(struct drm_i915_private *i915, u32 val)
> +{
> + bool ddi_a_present = i915->vbt.ddi_port_info[PORT_A].child != NULL;
> + bool ddi_d_present = i915->vbt.ddi_port_info[PORT_D].child != NULL;
> + bool dsi_present = intel_bios_is_dsi_present(i915, NULL);
> +
> + /*
> + * VBT's 'dvo port' field for child devices references the DDI, not
> + * the PHY. So if combo PHY A is wired up to drive an external
> + * display, we should see a child device present on PORT_D and
> + * nothing on PORT_A and no DSI.
> + */
> + if (ddi_d_present && !ddi_a_present && !dsi_present)
> + return val | ICL_PHY_MISC_MUX_DDID;
> +
> + /*
> + * If we encounter a VBT that claims to have an external display on
> + * DDI-D _and_ an internal display on DDI-A/DSI leave an error message
> + * in the log and let the internal display win.
> + */
> + if (ddi_d_present)
> + DRM_ERROR("VBT claims to have both internal and external displays on PHY A. Configuring for internal.\n");
> +
> + return val & ~ICL_PHY_MISC_MUX_DDID;
> +}
> +
> static void icl_combo_phys_init(struct drm_i915_private *dev_priv)
> {
> enum port port;
> @@ -273,7 +299,17 @@ static void icl_combo_phys_init(struct drm_i915_private *dev_priv)
> continue;
> }
>
> + /*
> + * EHL's combo PHY A can be hooked up to either an external
> + * display (via DDI-D) or an internal display (via DDI-A or
> + * the DSI DPHY). This is a motherboard design decision that
> + * can't be changed on the fly, so initialize the PHY's mux
> + * based on whether our VBT indicates the presence of any
> + * "internal" child devices.
> + */
> val = I915_READ(ICL_PHY_MISC(port));
> + if (!IS_ICELAKE(dev_priv) && port == PORT_A)

Maybe IS_EHL instead?

Patch is
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

> + val = ehl_combo_phy_a_mux(dev_priv, val);
> val &= ~ICL_PHY_MISC_DE_IO_COMP_PWR_DOWN;
> I915_WRITE(ICL_PHY_MISC(port), val);
>
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 1ae36b9efc85..68afafafd312 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -11138,6 +11138,7 @@ enum skl_power_gate {
> #define _ICL_PHY_MISC_B 0x64C04
> #define ICL_PHY_MISC(port) _MMIO_PORT(port, _ICL_PHY_MISC_A, \
> _ICL_PHY_MISC_B)
> +#define ICL_PHY_MISC_MUX_DDID (1 << 28)
> #define ICL_PHY_MISC_DE_IO_COMP_PWR_DOWN (1 << 23)
>
> /* Icelake Display Stream Compression Registers */
> --
> 2.17.2

--
Ville Syrjälä
Intel