Re: [PATCH 14/14] drm/imx: dc: Use prefetch engine

On 09/19/2025, Frank Li wrote:

On Fri, Jul 04, 2025 at 05:04:01PM +0800, Liu Ying wrote:

quoted

One prefetch engine consists of one DPR channel and one or two PRGs.
Each PRG handles one planar in a pixel format.  Every FetchUnit used
by KMS may attach to a PRG and hence use a prefetch engine.  So, to
simplify driver code, always use prefetch engines for FetchUnits in
KMS driver and avoid supporting bypassing them.  Aside from configuring
and disabling a prefetch engine along with a FetchUnit for atomic
commits, properly disable the prefetch engine at boot and adapt burst
size/stride fixup requirements from PRG in FetchUnit driver.

Signed-off-by: Liu Ying <victor.liu@nxp.com>
---
 drivers/gpu/drm/imx/dc/dc-crtc.c  | 139 +++++++++++++++++++++++++++++++++++---
 drivers/gpu/drm/imx/dc/dc-fu.c    |  27 +++++++-
 drivers/gpu/drm/imx/dc/dc-fu.h    |   2 +-
 drivers/gpu/drm/imx/dc/dc-kms.h   |   5 ++
 drivers/gpu/drm/imx/dc/dc-plane.c |  46 +++++++++++--
 5 files changed, 197 insertions(+), 22 deletions(-)

diff --git a/drivers/gpu/drm/imx/dc/dc-crtc.c b/drivers/gpu/drm/imx/dc/dc-crtc.c
index 9e9e86cd5202bcb0bb4d5627dbcefcc3f4e2ead0..4c7aab360616cb1c84c31c83f16df703b1c2c6d7 100644
--- a/drivers/gpu/drm/imx/dc/dc-crtc.c
+++ b/drivers/gpu/drm/imx/dc/dc-crtc.c

@@ -25,6 +25,7 @@
 #include <drm/drm_vblank.h>

 #include "dc-de.h"
+#include "dc-dprc.h"
 #include "dc-drv.h"
 #include "dc-kms.h"
 #include "dc-pe.h"

@@ -204,7 +205,13 @@ dc_crtc_atomic_flush(struct drm_crtc *crtc, struct drm_atomic_state *state)
 				drm_atomic_get_old_crtc_state(state, crtc);
 	struct drm_crtc_state *new_crtc_state =
 				drm_atomic_get_new_crtc_state(state, crtc);
+	struct drm_plane_state *old_plane_state =
+			drm_atomic_get_old_plane_state(state, crtc->primary);
+	struct drm_plane_state *new_plane_state =
+			drm_atomic_get_new_plane_state(state, crtc->primary);
+	struct dc_plane *dc_plane = to_dc_plane(crtc->primary);
 	struct dc_crtc *dc_crtc = to_dc_crtc(crtc);
+	bool disabling_plane;
 	int idx;

 	if (drm_atomic_crtc_needs_modeset(new_crtc_state) ||

@@ -216,13 +223,40 @@ dc_crtc_atomic_flush(struct drm_crtc *crtc, struct drm_atomic_state *state)

 	enable_irq(dc_crtc->irq_ed_cont_shdload);

-	/* flush plane update out to display */
-	dc_ed_pec_sync_trigger(dc_crtc->ed_cont);
+	disabling_plane = drm_atomic_plane_disabling(old_plane_state,
+						     new_plane_state);
+
+	if (disabling_plane) {
+		unsigned long flags;
+
+		dc_crtc_dbg(crtc, "disabling plane\n");
+
+		/*
+		 * Don't relinquish CPU until DPRC REPEAT_EN is disabled and
+		 * sync is triggered.
+		 */
+		local_irq_save(flags);
+		preempt_disable();
+
+		DC_CRTC_WAIT_FOR_FRAMEGEN_FRAME_INDEX_MOVING(dc_crtc->fg);
+		dc_dprc_disable_repeat_en(dc_plane->fu->dprc);
+		/* flush plane update out to display */
+		dc_ed_pec_sync_trigger(dc_crtc->ed_cont);
+
+		local_irq_restore(flags);
+		preempt_enable();

preempt_enable();
local_irq_restore(flags);

Like I replied to your comment on patch 8, see
__raw_spin_lock_irqsave() and __raw_spin_unlock_irqrestore().

look symmetry() with enter this sections.

Sorry, I don't understand your point here.
Function symmetry()?  Where is it defined?

quoted

+	} else {
+		/* flush plane update out to display */
+		dc_ed_pec_sync_trigger(dc_crtc->ed_cont);
+	}

 	DC_CRTC_WAIT_FOR_COMPLETION_TIMEOUT(ed_cont_shdload_done);

 	disable_irq(dc_crtc->irq_ed_cont_shdload);

+	if (disabling_plane)
+		dc_dprc_disable(dc_plane->fu->dprc);
+
 	DC_CRTC_CHECK_FRAMEGEN_FIFO(dc_crtc->fg);

 	drm_dev_exit(idx);

@@ -320,14 +354,33 @@ dc_crtc_atomic_enable(struct drm_crtc *crtc, struct drm_atomic_state *state)
 	dc_crtc_queue_state_event(new_crtc_state);
 }

...

quoted

+	struct drm_crtc_state *old_crtc_state =
+				drm_atomic_get_old_crtc_state(state, crtc);
 	struct dc_drm_device *dc_drm = to_dc_drm_device(crtc->dev);
+	struct dc_plane *dc_plane = to_dc_plane(crtc->primary);
 	struct dc_crtc *dc_crtc = to_dc_crtc(crtc);
 	int idx, ret;

 	if (!drm_dev_enter(crtc->dev, &idx))
 		goto out;

-	__dc_crtc_disable_fg(crtc);
+	enable_irq(dc_crtc->irq_dec_seqcomplete);
+
+	if (old_crtc_state->plane_mask)
+		__dc_crtc_disable_fg_along_with_dprc_repeat_en(crtc);
+	else
+		dc_fg_disable(dc_crtc->fg);
+
+	DC_CRTC_WAIT_FOR_COMPLETION_TIMEOUT(dec_seqcomplete_done);
+	disable_irq(dc_crtc->irq_dec_seqcomplete);

Are you sure irq is disabled when call this function?

Same here, I don't get your point/question.

If you mean IRQ dc_crtc->irq_dec_seqcomplete, then it's disabled after
calling this function.

Frank

quoted

+
+	if (old_crtc_state->plane_mask)
+		dc_dprc_disable(dc_plane->fu->dprc);
+
 	dc_fg_disable_clock(dc_crtc->fg);

 	/* request pixel engine power-off as plane is off too */

@@ -373,7 +441,10 @@ dc_crtc_atomic_disable(struct drm_crtc *crtc, struct drm_atomic_state *state)
 void dc_crtc_disable_at_boot(struct drm_crtc *crtc)
 {
 	struct dc_drm_device *dc_drm = to_dc_drm_device(crtc->dev);
+	struct dc_plane *dc_plane = to_dc_plane(crtc->primary);
 	struct dc_crtc *dc_crtc = to_dc_crtc(crtc);
+	enum dc_link_id ed_src, lb_sec;
+	bool disable_dprc = false;
 	int ret;

 	ret = pm_runtime_resume_and_get(dc_crtc->de->dev);

...

quoted

 	fu_ops->set_src_buf_dimensions(fu, DC_FETCHUNIT_FRAC0, src_w, src_h);
 	fu_ops->set_fmt(fu, DC_FETCHUNIT_FRAC0, fb->format);
 	fu_ops->set_framedimensions(fu, src_w, src_h);

@@ -161,6 +190,9 @@ dc_plane_atomic_update(struct drm_plane *plane, struct drm_atomic_state *state)

 	dc_plane_dbg(plane, "uses %s\n", fu_ops->get_name(fu));

+	dc_dprc_configure(fu->dprc, new_state->crtc->index, src_w, src_h,
+			  fb->pitches[0], fb->format, baseaddr, prefetch_start);
+
 	dc_lb_pec_dynamic_prim_sel(lb, dc_cf_get_link_id(dplane->cf));
 	dc_lb_pec_dynamic_sec_sel(lb, fu_ops->get_link_id(fu));
 	dc_lb_mode(lb, LB_BLEND);

--

2.34.1

-- 
Regards,
Liu Ying