drm/i915: Software workaround for getting the HW status of DSI Port C on BYT

Due to hardware limitations on BYT, MIPI Port C DPI Enable bit
does not get set. To check whether DSI Port C was enabled in BIOS,
check the Pipe B enable bit for DSI Port C. In hardware, DSI Port C
is linked with Pipe B.

v2: Addressed review comments of Jani, Nikula
    - Used platform checks for this software workaround for BYT

Signed-off-by: Gaurav K Singh <gaurav.k.singh@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
index 215d00429b04903fa408631de32438799f7a8f89..42b6d6f5cecccb71c06155322f790e507582f673 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dsi.c
+++ b/drivers/gpu/drm/i915/intel_dsi.c
@@ -398,8 +398,10 @@ static bool intel_dsi_get_hw_state(struct intel_encoder *encoder,
                                   enum pipe *pipe)
 {
        struct drm_i915_private *dev_priv = encoder->base.dev->dev_private;
+       struct intel_dsi *intel_dsi = enc_to_intel_dsi(&encoder->base);
+       struct drm_device *dev = encoder->base.dev;
        enum intel_display_power_domain power_domain;
-       u32 port_ctl, func;
+       u32 dpi_enabled, func;
        enum port port;
 
        DRM_DEBUG_KMS("\n");
@@ -409,13 +411,23 @@ static bool intel_dsi_get_hw_state(struct intel_encoder *encoder,
                return false;
 
        /* XXX: this only works for one DSI output */
-       for_each_dsi_port(port, (1 << PORT_A) | (1 << PORT_C)) {
-               port_ctl = I915_READ(MIPI_PORT_CTRL(port));
+       for_each_dsi_port(port, intel_dsi->ports) {
                func = I915_READ(MIPI_DSI_FUNC_PRG(port));
+               dpi_enabled = I915_READ(MIPI_PORT_CTRL(port)) &
+                                                       DPI_ENABLE;
+
+               /* Due to some hardware limitations on BYT, MIPI Port C DPI
+                * Enable bit does not get set. To check whether DSI Port C
+                * was enabled in BIOS, check the Pipe B enable bit
+                */
+               if (IS_VALLEYVIEW(dev) && !IS_CHERRYVIEW(dev) &&
+                   (port == PORT_C))
+                       dpi_enabled = I915_READ(PIPECONF(PIPE_B)) &
+                                                       PIPECONF_ENABLE;
 
-               if ((port_ctl & DPI_ENABLE) || (func & CMD_MODE_DATA_WIDTH_MASK)) {
+               if (dpi_enabled || (func & CMD_MODE_DATA_WIDTH_MASK)) {
                        if (I915_READ(MIPI_DEVICE_READY(port)) & DEVICE_READY) {
-                               *pipe = port == PORT_A ? PIPE_A : PIPE_C;
+                               *pipe = port == PORT_A ? PIPE_A : PIPE_B;
                                return true;
                        }
                }