linux-kernel - [PATCH v3 034/105] drm/vc4: crtc: Add FIFO depth to vc4_crtc

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Message-Id: <a213ce2bc6a4147506ce61f70dc2e388db54021c.1590594512.git-series.maxime@cerno.tech>
Date:   Wed, 27 May 2020 17:48:04 +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 v3 034/105] 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.

Signed-off-by: Maxime Ripard <maxime@...no.tech>
---
 drivers/gpu/drm/vc4/vc4_crtc.c | 19 ++++++++++++++++---
 drivers/gpu/drm/vc4/vc4_drv.h  |  3 +++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c
index a6c3f2f907bd..e25e81bf64e7 100644
--- a/drivers/gpu/drm/vc4/vc4_crtc.c
+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
@@ -248,10 +248,20 @@ vc4_crtc_update_gamma_lut(struct drm_crtc *crtc)
 	vc4_crtc_lut_load(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;
+	u32 fifo_len_bytes = vc4_crtc->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:
@@ -367,7 +377,7 @@ 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 |
@@ -1066,6 +1076,7 @@ static const struct vc4_crtc_data bcm2835_pv0_data = {
 	.hvs_available_channels = BIT(0),
 	.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,
@@ -1077,6 +1088,7 @@ static const struct vc4_crtc_data bcm2835_pv1_data = {
 	.hvs_available_channels = BIT(2),
 	.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,
@@ -1088,6 +1100,7 @@ static const struct vc4_crtc_data bcm2835_pv2_data = {
 	.hvs_available_channels = BIT(1),
 	.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 73156a53822f..1f62dffd6676 100644
--- a/drivers/gpu/drm/vc4/vc4_drv.h
+++ b/drivers/gpu/drm/vc4/vc4_drv.h
@@ -450,6 +450,9 @@ to_vc4_encoder(struct drm_encoder *encoder)
 }
 
 struct vc4_crtc_data {
+	/* Depth of the PixelValve FIFO in bytes */
+	unsigned int fifo_depth;
+
 	/* Which channels of the HVS can the output source from */
 	unsigned int hvs_available_channels;
 
-- 
git-series 0.9.1