linux-kernel - [PATCH v4 15/78] drm/vc4: crtc: Add FIFO depth to vc4_crtc

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Message-Id: <d5e351b43c779a13dfe320bd486f3215b85e063f.1594230107.git-series.maxime@cerno.tech>
Date:   Wed,  8 Jul 2020 19:41:23 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Eric Anholt <eric@...olt.net>
Cc:     dri-devel@...ts.freedesktop.org,
        linux-rpi-kernel@...ts.infradead.org,
        bcm-kernel-feedback-list@...adcom.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Phil Elwell <phil@...pberrypi.com>,
        Maxime Ripard <maxime@...no.tech>
Subject: [PATCH v4 15/78] drm/vc4: crtc: Add FIFO depth to vc4_crtc_data

Not all pixelvalve FIFOs in vc5 have the same depth, so we need to add that
to our vc4_crtc_data structure to be able to compute the fill level
properly later on.

Reviewed-by: Eric Anholt <eric@...olt.net>
Signed-off-by: Maxime Ripard <maxime@...no.tech>
---
 drivers/gpu/drm/vc4/vc4_crtc.c | 20 +++++++++++++++++---
 drivers/gpu/drm/vc4/vc4_drv.h  |  3 +++
 2 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index b7e47ce1476c..2c64efd2d3d9 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -206,10 +206,21 @@ void vc4_crtc_destroy(struct drm_crtc *crtc)
 	drm_crtc_cleanup(crtc);
 }
 
-static u32 vc4_get_fifo_full_level(u32 format)
+static u32 vc4_get_fifo_full_level(struct vc4_crtc *vc4_crtc, u32 format)
 {
-	static const u32 fifo_len_bytes = 64;
+	const struct vc4_pv_data *pv_data = vc4_crtc_to_vc4_pv_data(vc4_crtc);
+	u32 fifo_len_bytes = pv_data->fifo_depth;
 
+	/*
+	 * Pixels are pulled from the HVS if the number of bytes is
+	 * lower than the FIFO full level.
+	 *
+	 * The latency of the pixel fetch mechanism is 6 pixels, so we
+	 * need to convert those 6 pixels in bytes, depending on the
+	 * format, and then subtract that from the length of the FIFO
+	 * to make sure we never end up in a situation where the FIFO
+	 * is full.
+	 */
 	switch (format) {
 	case PV_CONTROL_FORMAT_DSIV_16:
 	case PV_CONTROL_FORMAT_DSIC_16:
@@ -326,7 +337,7 @@ static void vc4_crtc_config_pv(struct drm_crtc *crtc)
 
 	CRTC_WRITE(PV_CONTROL,
 		   VC4_SET_FIELD(format, PV_CONTROL_FORMAT) |
-		   VC4_SET_FIELD(vc4_get_fifo_full_level(format),
+		   VC4_SET_FIELD(vc4_get_fifo_full_level(vc4_crtc, format),
 				 PV_CONTROL_FIFO_LEVEL) |
 		   VC4_SET_FIELD(pixel_rep - 1, PV_CONTROL_PIXEL_REP) |
 		   PV_CONTROL_CLR_AT_START |
@@ -785,6 +796,7 @@ static const struct vc4_pv_data bcm2835_pv0_data = {
 		.hvs_output = 0,
 	},
 	.debugfs_name = "crtc0_regs",
+	.fifo_depth = 64,
 	.pixels_per_clock = 1,
 	.encoder_types = {
 		[PV_CONTROL_CLK_SELECT_DSI] = VC4_ENCODER_TYPE_DSI0,
@@ -798,6 +810,7 @@ static const struct vc4_pv_data bcm2835_pv1_data = {
 		.hvs_output = 2,
 	},
 	.debugfs_name = "crtc1_regs",
+	.fifo_depth = 64,
 	.pixels_per_clock = 1,
 	.encoder_types = {
 		[PV_CONTROL_CLK_SELECT_DSI] = VC4_ENCODER_TYPE_DSI1,
@@ -811,6 +824,7 @@ static const struct vc4_pv_data bcm2835_pv2_data = {
 		.hvs_output = 1,
 	},
 	.debugfs_name = "crtc2_regs",
+	.fifo_depth = 64,
 	.pixels_per_clock = 1,
 	.encoder_types = {
 		[PV_CONTROL_CLK_SELECT_DPI_SMI_HDMI] = VC4_ENCODER_TYPE_HDMI,
diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h
index 9e81ad8331f1..179010b9a010 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.h
+++ b/drivers/gpu/drm/vc4/vc4_drv.h
@@ -457,6 +457,9 @@ struct vc4_crtc_data {
 struct vc4_pv_data {
 	struct vc4_crtc_data	base;
 
+	/* Depth of the PixelValve FIFO in bytes */
+	unsigned int fifo_depth;
+
 	/* Number of pixels output per clock period */
 	u8 pixels_per_clock;
 
-- 
git-series 0.9.1