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

Liu Ying
2025-09-22T03:54:28Z

On 09/19/2025, Frank Li wrote:
> On Fri, Jul 04, 2025 at 05:04:01PM +0800, Liu Ying wrote:
>> 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?

>
>> + } 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);
>> }
>>
>
> ...
>
>> + 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
>> +
>> + 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);
> ...
>
>> 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