Hi Sam,
Le mar. 30 juin 2020 à 13:44, Sam Ravnborg <s...@ravnborg.org> a écrit
:
Hi Paul.
On Tue, Jun 30, 2020 at 01:52:06AM +0200, Paul Cercueil wrote:
The address of the DMA descriptor never changes. It can therefore
be set
in the probe function.
Signed-off-by: Paul Cercueil <p...@crapouillou.net>
---
Notes:
v2: No change
drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
index 924c8daf071a..f7b0c5dc8cd8 100644
--- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
+++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
@@ -358,8 +358,6 @@ static void
ingenic_drm_crtc_atomic_flush(struct drm_crtc *crtc,
ingenic_drm_crtc_update_ctrl(priv, finfo);
clk_set_rate(priv->pix_clk, state->adjusted_mode.clock * 1000);
-
- regmap_write(priv->map, JZ_REG_LCD_DA0, priv->dma_hwdesc->next);
}
if (event) {
@@ -757,6 +755,9 @@ static int ingenic_drm_probe(struct
platform_device *pdev)
}
}
+ /* Set address of our DMA descriptor chain */
+ regmap_write(priv->map, JZ_REG_LCD_DA0, priv->dma_hwdesc_phys);
+
What is the purpose of this code after the assignment was moved:
static int ingenic_drm_probe(struct platform_device *pdev)
{
...
priv->dma_hwdesc->next = priv->dma_hwdesc_phys;
I do not see ->next used anymore.
Could this assignment be dropped?
And the following line:
priv->dma_hwdesc->id = 0xdeafbead;
I can only see ->id be assingned, it is never referenced??
Maybe this is all related to the structure assumed by the data pointed
to by JZ_REG_LCD_DA0?
As its name suggests, 'dma_hwdesc' points to a DMA hardware descriptor.
Setting ->next sets the address of the next descriptor (which is itself
since we only use one descriptor). The 'id' field will be copied by the
hardware to a register when the DMA descriptor is loaded, so we can
know from userspace (debugfs) what DMA descriptors are loaded by
looking up the IDs.
-Paul
Sam
ret = drm_dev_register(drm, 0);
if (ret) {
dev_err(dev, "Failed to register DRM driver\n");
--
2.27.0
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