Re: [PATCH 08/14] drm/imx: dc: Use TCON operation mode

[Frank Li <Frank.li@nxp.com>]

On Fri, Jul 04, 2025 at 05:03:55PM +0800, Liu Ying wrote:
> In TCON operation mode, sync signals from FrameGen are ignored, but
> a much more customized output timing can be generated by the TCON
> module.  By using TCON operaton mode, generate KACHUNK signal along
> with HSYNC/VSYNC/data enable signals.  The KACHUNK signal is used as
> a synchronization signal inside the prefetch engine(DPRC + PRG(s),
> attached to FetchUnit(s)).  Carefully switch TCON bypass mode to TCON
> operation mode when CRTC is being enabled so that the prefetch engine
> may evade the first dumb frame generated by the display controller.
>
> Since TCON BYPASS bit is controlled by KMS driver when doing atomic
> commits, drop the bit setting when initializing TCON.  This also
> avoids accidentally initializing TCON BYPASS bit to 1 when driver
> module removing and re-installing where an upcoming patch would
> disable a CRTC at boot in TCON operation mode if needed.
>
> Signed-off-by: Liu Ying <victor.liu@nxp.com>
> ---
>  drivers/gpu/drm/imx/dc/dc-crtc.c |  28 ++++++++++
>  drivers/gpu/drm/imx/dc/dc-de.h   |   2 +
>  drivers/gpu/drm/imx/dc/dc-kms.h  |   2 +
>  drivers/gpu/drm/imx/dc/dc-tc.c   | 114 +++++++++++++++++++++++++++++++++++++--
>  4 files changed, 142 insertions(+), 4 deletions(-)
>
...
> @@ -249,6 +260,7 @@ dc_crtc_atomic_enable(struct drm_crtc *crtc, struct drm_atomic_state *state)
>  	enable_irq(dc_crtc->irq_ed_safe_shdload);
>
>  	dc_fg_cfg_videomode(dc_crtc->fg, adj);
> +	dc_tc_cfg_videomode(dc_crtc->tc, adj);
>
>  	dc_cf_framedimensions(dc_crtc->cf_cont,
>  			      adj->crtc_hdisplay, adj->crtc_vdisplay);
> @@ -273,7 +285,22 @@ dc_crtc_atomic_enable(struct drm_crtc *crtc, struct drm_atomic_state *state)
>  	dc_ed_pec_sync_trigger(dc_crtc->ed_cont);
>  	dc_ed_pec_sync_trigger(dc_crtc->ed_safe);
>  	dc_fg_shdtokgen(dc_crtc->fg);
> +
> +	/* Don't relinquish CPU until TCON is set to operation mode. */
> +	local_irq_save(flags);
> +	preempt_disable();
> +
>  	dc_fg_enable(dc_crtc->fg);
> +	/*
> +	 * Turn TCON into operation mode as soon as the first dumb
> +	 * frame is generated by DC(we don't relinquish CPU to ensure
> +	 * this).  This makes DPR/PRG be able to evade the frame.
> +	 */
> +	DC_CRTC_WAIT_FOR_FRAMEGEN_FRAME_INDEX_MOVING(dc_crtc->fg);
> +	dc_tc_set_operation_mode(dc_crtc->tc);
> +
> +	local_irq_restore(flags);
> +	preempt_enable();

Does it need reverised order?

>
>  	DC_CRTC_WAIT_FOR_COMPLETION_TIMEOUT(ed_safe_shdload_done);
>  	DC_CRTC_WAIT_FOR_COMPLETION_TIMEOUT(ed_cont_shdload_done);
> @@ -561,6 +588,7 @@ int dc_crtc_init(struct dc_drm_device *dc_drm, int crtc_index)
>  	dc_crtc->ed_cont = pe->ed_cont[crtc_index];
>  	dc_crtc->ed_safe = pe->ed_safe[crtc_index];
>  	dc_crtc->fg = de->fg;
> +	dc_crtc->tc = de->tc;
>
>  	dc_crtc->irq_dec_framecomplete = de->irq_framecomplete;
>  	dc_crtc->irq_dec_seqcomplete = de->irq_seqcomplete;
> diff --git a/drivers/gpu/drm/imx/dc/dc-de.h b/drivers/gpu/drm/imx/dc/dc-de.h
> index 211f3fcc1a9ad642617d3b22e35ea923f75e645b..c39f2ef5eea98c3eb6ae9b5392f9bf9f7e33e7c5 100644
> --- a/drivers/gpu/drm/imx/dc/dc-de.h
> +++ b/drivers/gpu/drm/imx/dc/dc-de.h
> @@ -54,6 +54,8 @@ enum drm_mode_status dc_fg_check_clock(struct dc_fg *fg, int clk_khz);
>  void dc_fg_init(struct dc_fg *fg);
>
...

>
> --
> 2.34.1
>