[PATCH 2/2] drm/vc4: Squash commit for Mario's precise vblank timestamping.

[Eric Anholt <eric@anholt.net>]

Read out the DISPBASE registers to decide on the FIFO size.

Signed-off-by: Eric Anholt <eric@anholt.net>
---

Mario: How about this for a squash into your commit?  Here are the
values I dumped for cob_size:

[    2.148314] [drm] Scaler 0 size 5232
[    2.162239] [drm] Scaler 2 size 2048
[    2.172957] [drm] Scaler 1 size 13456

 drivers/gpu/drm/vc4/vc4_crtc.c | 23 +++++++++++++++++++++--
 drivers/gpu/drm/vc4/vc4_regs.h | 18 +++++++++++++++++-
 2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index baf962bce063..3b7db17c356d 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -55,6 +55,8 @@ struct vc4_crtc {
 	u8 lut_r[256];
 	u8 lut_g[256];
 	u8 lut_b[256];
+	/* Size in pixels of the COB memory allocated to this CRTC. */
+	u32 cob_size;
 
 	struct drm_pending_vblank_event *event;
 };
@@ -195,8 +197,7 @@ int vc4_crtc_get_scanoutpos(struct drm_device *dev, unsigned int crtc_id,
 		*hpos = 0;
 
 	/* This is the offset we need for translating hvs -> pv scanout pos. */
-	/* XXX Find proper formula from hw docs instead of guesstimating? */
-	fifo_lines = 2048 * 7 / mode->crtc_hdisplay;
+	fifo_lines = vc4_crtc->cob_size / mode->crtc_hdisplay;
 
 	if (fifo_lines > 0)
 		ret |= DRM_SCANOUTPOS_VALID;
@@ -873,6 +874,22 @@ static void vc4_set_crtc_possible_masks(struct drm_device *drm,
 	}
 }
 
+static void
+vc4_crtc_get_cob_allocation(struct vc4_crtc *vc4_crtc)
+{
+	struct drm_device *drm = vc4_crtc->base.dev;
+	struct vc4_dev *vc4 = to_vc4_dev(drm);
+	u32 dispbase = HVS_READ(SCALER_DISPBASEX(vc4_crtc->channel));
+	/* Top/base are supposed to be 4-pixel aligned, but the
+	 * Raspberry Pi firmware fills the low bits (which are
+	 * presumably ignored).
+	 */
+	u32 top = VC4_GET_FIELD(dispbase, SCALER_DISPBASEX_TOP) & ~3;
+	u32 base = VC4_GET_FIELD(dispbase, SCALER_DISPBASEX_BASE) & ~3;
+
+	vc4_crtc->cob_size = top - base + 4;
+}
+
 static int vc4_crtc_bind(struct device *dev, struct device *master, void *data)
 {
 	struct platform_device *pdev = to_platform_device(dev);
@@ -949,6 +966,8 @@ static int vc4_crtc_bind(struct device *dev, struct device *master, void *data)
 		crtc->cursor = cursor_plane;
 	}
 
+	vc4_crtc_get_cob_allocation(vc4_crtc);
+
 	CRTC_WRITE(PV_INTEN, 0);
 	CRTC_WRITE(PV_INTSTAT, PV_INT_VFP_START);
 	ret = devm_request_irq(dev, platform_get_irq(pdev, 0),
diff --git a/drivers/gpu/drm/vc4/vc4_regs.h b/drivers/gpu/drm/vc4/vc4_regs.h
index 63cdc28ff7bb..160942a9180e 100644
--- a/drivers/gpu/drm/vc4/vc4_regs.h
+++ b/drivers/gpu/drm/vc4/vc4_regs.h
@@ -366,7 +366,6 @@
 # define SCALER_DISPBKGND_FILL			BIT(24)
 
 #define SCALER_DISPSTAT0                        0x00000048
-#define SCALER_DISPBASE0                        0x0000004c
 # define SCALER_DISPSTATX_MODE_MASK		VC4_MASK(31, 30)
 # define SCALER_DISPSTATX_MODE_SHIFT		30
 # define SCALER_DISPSTATX_MODE_DISABLED		0
@@ -379,6 +378,20 @@
 # define SCALER_DISPSTATX_FRAME_COUNT_SHIFT	12
 # define SCALER_DISPSTATX_LINE_MASK		VC4_MASK(11, 0)
 # define SCALER_DISPSTATX_LINE_SHIFT		0
+
+#define SCALER_DISPBASE0                        0x0000004c
+/* Last pixel in the COB (display FIFO memory) allocated to this HVS
+ * channel.  Must be 4-pixel aligned (and thus 4 pixels less than the
+ * next COB base).
+ */
+# define SCALER_DISPBASEX_TOP_MASK		VC4_MASK(31, 16)
+# define SCALER_DISPBASEX_TOP_SHIFT		16
+/* First pixel in the COB (display FIFO memory) allocated to this HVS
+ * channel.  Must be 4-pixel aligned.
+ */
+# define SCALER_DISPBASEX_BASE_MASK		VC4_MASK(15, 0)
+# define SCALER_DISPBASEX_BASE_SHIFT		0
+
 #define SCALER_DISPCTRL1                        0x00000050
 #define SCALER_DISPBKGND1                       0x00000054
 #define SCALER_DISPBKGNDX(x)			(SCALER_DISPBKGND0 +        \
@@ -389,6 +402,9 @@
 						 (x) * (SCALER_DISPSTAT1 - \
 							SCALER_DISPSTAT0))
 #define SCALER_DISPBASE1                        0x0000005c
+#define SCALER_DISPBASEX(x)			(SCALER_DISPBASE0 +        \
+						 (x) * (SCALER_DISPBASE1 - \
+							SCALER_DISPBASE0))
 #define SCALER_DISPCTRL2                        0x00000060
 #define SCALER_DISPCTRLX(x)			(SCALER_DISPCTRL0 +        \
 						 (x) * (SCALER_DISPCTRL1 - \
-- 
2.8.1