linux-kernel - [PATCH v1 1/3] drm/tegra: dc: Tune up high priority request controls on Tegra20

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Date:   Sun,  5 May 2019 20:37:05 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v1 1/3] drm/tegra: dc: Tune up high priority request controls on Tegra20

Tegra20 has a high priority request control that allow to configure
when display's memory client should perform read requests with a higher
priority (Tegra30+ uses other means). Set up the controls for a more
aggressive prefetching to reliably avoid FIFO underflow on a lower memory
frequency, this allow to safely drop the memory bandwidth requirement by
about two times in a most popular cases (only one display active, video
overlay inactive, no scaling is done).

Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/gpu/drm/tegra/dc.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
index 607a6ea17ecc..cf622a07e9b6 100644
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -1833,12 +1833,12 @@ static void tegra_crtc_atomic_enable(struct drm_crtc *crtc,
 		tegra_dc_writel(dc, value, DC_CMD_INT_POLARITY);
 
 		/* initialize timer */
-		value = CURSOR_THRESHOLD(0) | WINDOW_A_THRESHOLD(0x20) |
-			WINDOW_B_THRESHOLD(0x20) | WINDOW_C_THRESHOLD(0x20);
+		value = CURSOR_THRESHOLD(0) | WINDOW_A_THRESHOLD(0x70) |
+			WINDOW_B_THRESHOLD(0x30) | WINDOW_C_THRESHOLD(0x70);
 		tegra_dc_writel(dc, value, DC_DISP_DISP_MEM_HIGH_PRIORITY);
 
-		value = CURSOR_THRESHOLD(0) | WINDOW_A_THRESHOLD(1) |
-			WINDOW_B_THRESHOLD(1) | WINDOW_C_THRESHOLD(1);
+		value = CURSOR_THRESHOLD(0) | WINDOW_A_THRESHOLD(0) |
+			WINDOW_B_THRESHOLD(0) | WINDOW_C_THRESHOLD(0);
 		tegra_dc_writel(dc, value, DC_DISP_DISP_MEM_HIGH_PRIORITY_TIMER);
 
 		value = VBLANK_INT | WIN_A_UF_INT | WIN_B_UF_INT | WIN_C_UF_INT |
-- 
2.21.0