[Intel-gfx] [PATCH 2/2] drm/i915/BXT: Tolerance at BXT DSI pipe_config comparison

[Ramalingam C]

At BXT DSI, PIPE registers are inactive. So we can't get the
PIPE's mode parameters from them. The possible option is
retriving them from the PORT registers. But mode timing
parameters are progammed to port registers interms of byteclocks.

The formula used to convert the pixels interms of byteclk is
	DIV_ROUND_UP(DIV_ROUND_UP(pixels * bpp * burst_mode_ratio,
 						8 * 100), lane_count);

So we retrieve them, interms of pixels as
	DIV_ROUND_UP((clk_hs * lane_count * 8 * 100),
					(bpp * burst_mode_ratio));

Due to the multiple DIV_ROUND_UP in both formulas we get the worst
case delta in the retrieved PIPE's timing parameter as below
	DIV_ROUND_UP((8 * intel_dsi->lane_count * 100),
		(dsi_pixel_format_bpp(intel_dsi->pixel_format) *
			intel_dsi->burst_mode_ratio)))

This converson of byteclk to pixel is required for hsync, hfp and hbp.
Which intern impacts horrizontal timing parameters. At worst case to
get htotal all there parameters are added with hactive.
Hence delta will be 3 times of above formula. Hence this value is
considered as tolerance for pipe_config comparison, in case of BXT DSI.

Signed-off-by: Ramalingam C <ramalingam.c at intel.com>
---
Reviewed at https://lists.freedesktop.org/archives/intel-gfx/2016-March/089548.html

 drivers/gpu/drm/i915/intel_display.c |   62 +++++++++++++++++++++++++++++++---
 1 file changed, 57 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index c0627d6..282f036 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -12557,6 +12557,9 @@ intel_pipe_config_compare(struct drm_device *dev,
 			  bool adjust)
 {
 	bool ret = true;
+	struct intel_crtc *crtc = to_intel_crtc(current_config->base.crtc);
+	struct intel_encoder *intel_encoder;
+	struct intel_dsi *intel_dsi = NULL;
 
 #define INTEL_ERR_OR_DBG_KMS(fmt, ...) \
 	do { \
@@ -12593,6 +12596,54 @@ intel_pipe_config_compare(struct drm_device *dev,
 		ret = false; \
 	}
 
+/*
+ * In case of BXT DSI, HW pipe_config will be retrieved from the port's timing
+ * configuration. This retrival includes some errors due to the DIV_ROUND_UP.
+ * So we are considering the max possible error at the comparison.
+ */
+/*
+ * htotal = hactive + hfp + hsync + hbp. Here last three lements might have
+ * the converson error, hence we consider the 3 times of error as tolerance.
+ */
+
+#define MAX_BXT_DSI_TIMING_RETRIVAL_ERR \
+		(intel_dsi == NULL ? 0 : \
+		DIV_ROUND_UP((3 * 8 * intel_dsi->lane_count * 100), \
+		(dsi_pixel_format_bpp(intel_dsi->pixel_format) * \
+			intel_dsi->burst_mode_ratio)))
+
+#define BXT_DSI_PIPE_CONF_CHECK_I_RANGE(name) { \
+	for_each_encoder_on_crtc(dev, &crtc->base, \
+					intel_encoder) { \
+		if (intel_encoder->type == INTEL_OUTPUT_DSI) { \
+			intel_dsi = enc_to_intel_dsi(&intel_encoder->base); \
+		} \
+	} \
+	if (!(current_config->name < pipe_config->name && \
+		current_config->name >= (pipe_config->name - \
+			MAX_BXT_DSI_TIMING_RETRIVAL_ERR))) { \
+		INTEL_ERR_OR_DBG_KMS("mismatch in " #name " " \
+		  "(expected %i, found %i(Err tolerance considered))\n", \
+		  current_config->name, \
+		  pipe_config->name); \
+		ret = false; \
+	} \
+}
+
+#define PIPE_CONF_CHECK_I_RANGE(name) { \
+	if (current_config->name != pipe_config->name) { \
+		if (IS_BROXTON(dev) && crtc->config->has_dsi_encoder) { \
+			BXT_DSI_PIPE_CONF_CHECK_I_RANGE(name) \
+		} else { \
+			INTEL_ERR_OR_DBG_KMS("mismatch in " #name " " \
+			  "(expected %i, found %i)\n", \
+			  current_config->name, \
+			  pipe_config->name); \
+			ret = false; \
+		} \
+	} \
+}
+
 #define PIPE_CONF_CHECK_M_N(name) \
 	if (!intel_compare_link_m_n(&current_config->name, \
 				    &pipe_config->name,\
@@ -12697,11 +12748,11 @@ intel_pipe_config_compare(struct drm_device *dev,
 	PIPE_CONF_CHECK_I(has_dsi_encoder);
 
 	PIPE_CONF_CHECK_I(base.adjusted_mode.crtc_hdisplay);
-	PIPE_CONF_CHECK_I(base.adjusted_mode.crtc_htotal);
-	PIPE_CONF_CHECK_I(base.adjusted_mode.crtc_hblank_start);
-	PIPE_CONF_CHECK_I(base.adjusted_mode.crtc_hblank_end);
-	PIPE_CONF_CHECK_I(base.adjusted_mode.crtc_hsync_start);
-	PIPE_CONF_CHECK_I(base.adjusted_mode.crtc_hsync_end);
+	PIPE_CONF_CHECK_I_RANGE(base.adjusted_mode.crtc_htotal);
+	PIPE_CONF_CHECK_I_RANGE(base.adjusted_mode.crtc_hblank_start);
+	PIPE_CONF_CHECK_I_RANGE(base.adjusted_mode.crtc_hblank_end);
+	PIPE_CONF_CHECK_I_RANGE(base.adjusted_mode.crtc_hsync_start);
+	PIPE_CONF_CHECK_I_RANGE(base.adjusted_mode.crtc_hsync_end);
 
 	PIPE_CONF_CHECK_I(base.adjusted_mode.crtc_vdisplay);
 	PIPE_CONF_CHECK_I(base.adjusted_mode.crtc_vtotal);
@@ -12779,6 +12830,7 @@ intel_pipe_config_compare(struct drm_device *dev,
 
 #undef PIPE_CONF_CHECK_X
 #undef PIPE_CONF_CHECK_I
+#undef PIPE_CONF_CHECK_I_RANGE
 #undef PIPE_CONF_CHECK_P
 #undef PIPE_CONF_CHECK_I_ALT
 #undef PIPE_CONF_CHECK_FLAGS
-- 
1.7.9.5