[PATCH] drm/i915: Enable scanline read for gen9 dsi

From: Vidya Srinivas <vidya.srinivas@intel.com>
To: intel-gfx@lists.freedesktop.org
Cc: Vidya Srinivas <vidya.srinivas@intel.com>
Subject: [PATCH] drm/i915: Enable scanline read for gen9 dsi
Date: Tue, 12 Sep 2017 19:25:36 +0530	[thread overview]
Message-ID: <1505224536-20965-1-git-send-email-vidya.srinivas@intel.com> (raw)
In-Reply-To: <E7C9878FBA1C6D42A1CA3F62AEB6945F7EFFB0B2@BGSMSX104.gar.corp.intel.com>

From: Uma Shankar <uma.shankar@intel.com>

For gen9 platforms, dsi timings are driven from port instead of pipe
(unlike ddi). Thus, we can't rely on pipe registers to get the timing
information. Even scanline register read will not be functional.
This is causing vblank evasion logic to fail since it relies on
scanline, causing atomic update failure warnings.

This patch uses pipe framestamp and current timestamp registers
to calculate scanline. This is an indirect way to get the scanline.
It helps resolve atomic update failure for gen9 dsi platforms.

v2: Addressed Ville and Daniel's review comments. Updated the
register MACROs, handled race condition for register reads,
extracted timings from the hwmode. Removed the dependency on
crtc->config to get the encoder type.

Credits-to: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Chandra Konduru <chandra.konduru@intel.com>
Signed-off-by: Vidya Srinivas <vidya.srinivas@intel.com>
---
 drivers/gpu/drm/i915/i915_drv.h  |  2 ++
 drivers/gpu/drm/i915/i915_irq.c  |  7 +++++
 drivers/gpu/drm/i915/i915_reg.h  | 11 ++++++++
 drivers/gpu/drm/i915/intel_dsi.c | 59 ++++++++++++++++++++++++++++++++++++++++
 4 files changed, 79 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 1cc31a5..fc84136 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -4085,6 +4085,8 @@ void intel_sbi_write(struct drm_i915_private *dev_priv, u16 reg, u32 value,
 u32 vlv_flisdsi_read(struct drm_i915_private *dev_priv, u32 reg);
 void vlv_flisdsi_write(struct drm_i915_private *dev_priv, u32 reg, u32 val);
 
+u32 bxt_dsi_get_scanline(struct intel_crtc *crtc);
+
 /* intel_dpio_phy.c */
 void bxt_port_to_phy_channel(struct drm_i915_private *dev_priv, enum port port,
 			     enum dpio_phy *phy, enum dpio_channel *ch);
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 5d391e6..40fa2cb 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -781,6 +781,7 @@ static int __intel_get_crtc_scanline(struct intel_crtc *crtc)
 	struct drm_vblank_crtc *vblank;
 	enum pipe pipe = crtc->pipe;
 	int position, vtotal;
+	struct intel_encoder *encoder;
 
 	if (!crtc->active)
 		return -1;
@@ -792,6 +793,12 @@ static int __intel_get_crtc_scanline(struct intel_crtc *crtc)
 	if (mode->flags & DRM_MODE_FLAG_INTERLACE)
 		vtotal /= 2;
 
+	if (IS_BROXTON(dev_priv) || IS_GEMINILAKE(dev_priv)) {
+		for_each_encoder_on_crtc(crtc->base.dev, &crtc->base, encoder)
+			if (encoder->type == INTEL_OUTPUT_DSI)
+				return bxt_dsi_get_scanline(crtc);
+	}
+
 	if (IS_GEN2(dev_priv))
 		position = I915_READ_FW(PIPEDSL(pipe)) & DSL_LINEMASK_GEN2;
 	else
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index 0b03260..864924c86 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -8802,6 +8802,17 @@ enum skl_power_gate {
 #define MIPIO_TXESC_CLK_DIV2			_MMIO(0x160008)
 #define  GLK_TX_ESC_CLK_DIV2_MASK			0x3FF
 
+/* Gen4+ Timestamp and Pipe Frame time stamp registers */
+#define GEN4_TIMESTAMP_CTR	_MMIO(MCHBAR_MIRROR_BASE + 0x2358)
+#define GEN7_TIMESTAMP_CTR	_MMIO(0x44070)
+
+#define _PIPE_FRMTMSTMP_A		0x70048
+#define _PIPE_FRMTMSTMP_B		0x71048
+#define _IVB_PIPE_FRMTMSTMP_C	0x72048
+#define PIPE_FRMTMSTMP(pipe)		\
+			_MMIO_PIPE3((pipe), _PIPE_FRMTMSTMP_A, \
+				_PIPE_FRMTMSTMP_A, _IVB_PIPE_FRMTMSTMP_C)
+
 /* BXT MIPI clock controls */
 #define BXT_MAX_VAR_OUTPUT_KHZ			39500
 
diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c
index 2a0f5d3..d000e01 100644
--- a/drivers/gpu/drm/i915/intel_dsi.c
+++ b/drivers/gpu/drm/i915/intel_dsi.c
@@ -1621,6 +1621,65 @@ static int intel_dsi_get_modes(struct drm_connector *connector)
 	return 1;
 }
 
+/*
+ * For Gen9 DSI, pipe scanline register will not
+ * work to get the scanline since the timings
+ * are driven from the PORT (unlike DDI encoders).
+ * This function will use Framestamp and current
+ * timestamp registers to calculate the scanline.
+ */
+u32 bxt_dsi_get_scanline(struct intel_crtc *crtc)
+{
+	struct drm_device *dev = crtc->base.dev;
+	struct drm_i915_private *dev_priv = to_i915(dev);
+	u32 crtc_vblank_start = crtc->base.mode.crtc_vblank_start;
+	u32 crtc_vtotal = crtc->base.mode.crtc_vtotal;
+	u32 crtc_htotal = crtc->base.mode.crtc_htotal;
+	u32 crtc_clock = crtc->base.mode.crtc_clock;
+	u64 scanline = 0, scan_prev_time, scan_curr_time, scan_post_time;
+
+	WARN_ON(!crtc_vtotal);
+	if (!crtc_vtotal)
+		return scanline;
+
+	/* To avoid the race condition where we might cross into the
+	 * next vblank just between the PIPE_FRMTMSTMP and TIMESTAMP_CTR
+	 * reads. We make sure we read PIPE_FRMTMSTMP and TIMESTAMP_CTR
+	 * during the same frame.
+	 */
+	do {
+		/*
+		 * This field provides read back of the display
+		 * pipe frame time stamp. The time stamp value
+		 * is sampled at every start of vertical blank.
+		 */
+		scan_prev_time = I915_READ_FW(PIPE_FRMTMSTMP(crtc->pipe));
+
+		/*
+		 * The TIMESTAMP_CTR register has the current
+		 * time stamp value.
+		 */
+		scan_curr_time = I915_READ_FW(GEN7_TIMESTAMP_CTR);
+
+		scan_post_time = I915_READ_FW(PIPE_FRMTMSTMP(crtc->pipe));
+	} while (scan_post_time != scan_prev_time);
+
+	/*
+	 * Since the register is 32 bit and the values
+	 * can overflow and wrap around, making sure
+	 * current time accounts for the register
+	 * wrap
+	 */
+	if (scan_curr_time < scan_prev_time)
+		scan_curr_time += 0x100000000;
+
+	scanline = div_u64(mul_u64_u32_shr((scan_curr_time - scan_prev_time),
+					crtc_clock, 0), 1000 * crtc_htotal);
+	scanline = (scanline + crtc_vblank_start) % crtc_vtotal;
+
+	return scanline;
+}
+
 static void intel_dsi_connector_destroy(struct drm_connector *connector)
 {
 	struct intel_connector *intel_connector = to_intel_connector(connector);
-- 
1.9.1

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