Re: [RFC 1/4] drm/sun4i: Wait for previous mixing process finish before committing next
flat view
From: Jernej Škrabec <hidden>
Date: 2019-12-29 09:17:09
Also in:
dri-devel, lkml
Hi! Dne sobota, 28. december 2019 ob 21:28:15 CET je roman.stratiienko@globallogic.com napisal(a):
From: Roman Stratiienko <redacted> Screen composition that requires dynamic layout modification, especially scaling is corrupted when layout changes. For example if one of the layer scales down, misaligned lines can be observed, and dynamic increasing of destination area makes mixer to hang and draw nothing after drawing modified layer. After deep investigation it turns that scaler double-buffered registers are not latched by GLB_DBUFFER bit, instead thay are latched immidiately. Only way to avoid artifacts is to change the registers after mixer finish previous frame. Similar was made in sunxi BSP - scaler register values was stored into RAM, and moved into registers at sync together with GLB_DBUFFER. Signed-off-by: Roman Stratiienko <redacted>
Nice catch! However, I'm a bit worried about blocking nature of this solution. What about shadowing scaler registers and applying them in "finish_irq" handler? You see, VI scaler can in some cases consume almost all time between two VSync events. That issue came up on A64 mixer1 with downscaling 4K videos in real time. I imagine that this solution might block for too long in this case. Check VI coarse scaling code: https://elixir.bootlin.com/linux/v5.5-rc3/source/drivers/gpu/drm/sun4i/ sun8i_vi_layer.c#L144
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--- drivers/gpu/drm/sun4i/sun8i_mixer.c | 15 +++++++++++++++ drivers/gpu/drm/sun4i/sun8i_mixer.h | 2 ++ 2 files changed, 17 insertions(+)diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.cb/drivers/gpu/drm/sun4i/sun8i_mixer.c index 8b803eb903b8..eea4813602b7 100644--- a/drivers/gpu/drm/sun4i/sun8i_mixer.c +++ b/drivers/gpu/drm/sun4i/sun8i_mixer.c@@ -257,6 +257,20 @@ const struct de2_fmt_info *sun8i_mixer_format_info(u32format) return NULL; } +static void sun8i_atomic_begin(struct sunxi_engine *engine, + struct drm_crtc_state *old_state) +{ + int reg, ret; + + ret = regmap_read_poll_timeout(engine->regs,
SUN8I_MIXER_GLOBAL_STATUS,
+ reg, + !(reg &
SUN8I_MIXER_GLOBAL_STATUS_BUSY),
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+ 200, 100000); + + if (ret) + pr_warn("%s: Wait for frame finish timeout\n", __func__);
Newly introduced drm_warn() should be used here. Best regards, Jernej
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+} + static void sun8i_mixer_commit(struct sunxi_engine *engine) { DRM_DEBUG_DRIVER("Committing changes\n");@@ -310,6 +324,7 @@ static struct drm_plane **sun8i_layers_init(structdrm_device *drm, static const struct sunxi_engine_ops sun8i_engine_ops = { .commit = sun8i_mixer_commit, .layers_init = sun8i_layers_init, + .atomic_begin = sun8i_atomic_begin, }; static struct regmap_config sun8i_mixer_regmap_config = {diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.hb/drivers/gpu/drm/sun4i/sun8i_mixer.h index c6cc94057faf..915479cc3077 100644--- a/drivers/gpu/drm/sun4i/sun8i_mixer.h +++ b/drivers/gpu/drm/sun4i/sun8i_mixer.h@@ -25,6 +25,8 @@ #define SUN8I_MIXER_GLOBAL_DBUFF_ENABLE BIT(0) +#define SUN8I_MIXER_GLOBAL_STATUS_BUSY BIT(4) + #define DE2_MIXER_UNIT_SIZE 0x6000 #define DE3_MIXER_UNIT_SIZE 0x3000
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