Hi Sam,
Le mar. 30 juin 2020 à 13:44, Sam Ravnborg sam@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 paul@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
dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel