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From:   Dmitry Osipenko <digetx@gmail.com>
To:     Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Georgi Djakov <georgi.djakov@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Peter De Schrijver <pdeschrijver@nvidia.com>,
        MyungJoo Ham <myungjoo.ham@samsung.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Chanwoo Choi <cw00.choi@samsung.com>,
        Mikko Perttunen <cyndis@kapsi.fi>
Cc:     =?UTF-8?q?Artur=20=C5=9Awigo=C5=84?= <a.swigon@samsung.com>,
        linux-tegra@vger.kernel.org, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        devicetree@vger.kernel.org
Subject: [PATCH v4 36/37] drm/tegra: dc: Tune up high priority request controls for Tegra20
Date:   Tue,  9 Jun 2020 16:14:03 +0300
Message-Id: <20200609131404.17523-37-digetx@gmail.com>
In-Reply-To: <20200609131404.17523-1-digetx@gmail.com>
References: <20200609131404.17523-1-digetx@gmail.com>
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Tegra20 has a high-priority-request control that allows to configure
when display's memory client should perform read requests with a higher
priority (Tegra30+ uses other means like Latency Allowance).

This patch changes the controls configuration in order to get a more
aggressive memory prefetching, which allows to reliably avoid FIFO
underflow when running on a lower memory frequency. This allow us
safely drop the memory bandwidth requirement by about two times in a
most popular use-cases (only one display active, video overlay inactive,
no scaling is done).

Signed-off-by: Dmitry Osipenko <digetx@gmail.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 12b318bb8475..48dad375b470 100644
--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -1971,12 +1971,12 @@ 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 |
-- 
2.26.0