Re: [RESEND PATCH v7 2/2] drm/tidss: Move OLDI mode validation to OLDI bridge mode_valid hook

[Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>]

Hi,

On 28/10/2025 05:39, Swamil Jain wrote:
> From: Jayesh Choudhary <j-choudhary@ti.com>
> 
> After integrating OLDI support[0], it is necessary to identify which VP
> instances use OLDI, since the OLDI driver owns the video port clock
> (as a serial clock). Clock operations on these VPs must be delegated to
> the OLDI driver, not handled by the TIDSS driver. This issue also
> emerged in upstream discussions when DSI-related clock management was
> attempted in the TIDSS driver[1].
> 
> To address this, add an 'is_ext_vp_clk' array to the 'tidss_device'
> structure, marking a VP as 'true' during 'tidss_oldi_init()' and as
> 'false' during 'tidss_oldi_deinit()'. TIDSS then uses 'is_ext_vp_clk'
> to skip clock validation checks in 'dispc_vp_mode_valid()' for VPs
> under OLDI control.
> 
> Since OLDI uses the DSS VP clock directly as a serial interface and
> manages its own rate, mode validation should be implemented in the OLDI
> bridge's 'mode_valid' hook. This patch adds that logic, ensuring proper
> delegation and avoiding spurious clock handling in the TIDSS driver.
> 
> [0]: https://lore.kernel.org/all/20250528122544.817829-1-aradhya.bhatia@linux.dev/
> [1]: https://lore.kernel.org/all/DA6TT575Z82D.3MPK8HG5GRL8U@kernel.org/
> 
> Fixes: 7246e0929945 ("drm/tidss: Add OLDI bridge support")
> Tested-by: Michael Walle <mwalle@kernel.org>
> Reviewed-by: Devarsh Thakkar <devarsht@ti.com>
> Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
> Signed-off-by: Swamil Jain <s-jain1@ti.com>
> ---
>  drivers/gpu/drm/tidss/tidss_dispc.c |  2 ++
>  drivers/gpu/drm/tidss/tidss_drv.h   |  2 ++
>  drivers/gpu/drm/tidss/tidss_oldi.c  | 21 +++++++++++++++++++++
>  3 files changed, 25 insertions(+)
> 
> diff --git a/drivers/gpu/drm/tidss/tidss_dispc.c b/drivers/gpu/drm/tidss/tidss_dispc.c
> index 07731b02490f..0c3337a7b163 100644
> --- a/drivers/gpu/drm/tidss/tidss_dispc.c
> +++ b/drivers/gpu/drm/tidss/tidss_dispc.c
> @@ -1315,6 +1315,8 @@ static int check_pixel_clock(struct dispc_device *dispc,
>  {
>  	unsigned long round_clock;
>  
> +	if (dispc->tidss->is_ext_vp_clk[hw_videoport])
> +		return 0;

Add empty line here. Also, add a short comment what this check is about.

>  	round_clock = clk_round_rate(dispc->vp_clk[hw_videoport], clock);
>  	/*
>  	 * To keep the check consistent with dispc_vp_set_clk_rate(), we
> diff --git a/drivers/gpu/drm/tidss/tidss_drv.h b/drivers/gpu/drm/tidss/tidss_drv.h
> index 84454a4855d1..e1c1f41d8b4b 100644
> --- a/drivers/gpu/drm/tidss/tidss_drv.h
> +++ b/drivers/gpu/drm/tidss/tidss_drv.h
> @@ -24,6 +24,8 @@ struct tidss_device {
>  
>  	const struct dispc_features *feat;
>  	struct dispc_device *dispc;
> +	bool is_ext_vp_clk[TIDSS_MAX_PORTS];
> +
>  
>  	unsigned int num_crtcs;
>  	struct drm_crtc *crtcs[TIDSS_MAX_PORTS];
> diff --git a/drivers/gpu/drm/tidss/tidss_oldi.c b/drivers/gpu/drm/tidss/tidss_oldi.c
> index 7688251beba2..d1a5fdac93ff 100644
> --- a/drivers/gpu/drm/tidss/tidss_oldi.c
> +++ b/drivers/gpu/drm/tidss/tidss_oldi.c
> @@ -309,6 +309,24 @@ static u32 *tidss_oldi_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
>  	return input_fmts;
>  }
>  
> +static enum drm_mode_status
> +tidss_oldi_mode_valid(struct drm_bridge *bridge,
> +		      const struct drm_display_info *info,
> +		      const struct drm_display_mode *mode)
> +{
> +	struct tidss_oldi *oldi = drm_bridge_to_tidss_oldi(bridge);
> +	unsigned long round_clock;
> +
> +	round_clock = clk_round_rate(oldi->serial, mode->clock * 7 * 1000);
> +	/*
> +	 * To keep the check consistent with dispc_vp_set_clk_rate(),
> +	 * we use the same 5% check here.
> +	 */
> +	if (dispc_pclk_diff(mode->clock * 7 * 1000, round_clock) > 5)
> +		return -EINVAL;

Add an empty line here.

Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

> +	return 0;
> +}
> +
>  static const struct drm_bridge_funcs tidss_oldi_bridge_funcs = {
>  	.attach	= tidss_oldi_bridge_attach,
>  	.atomic_pre_enable = tidss_oldi_atomic_pre_enable,
> @@ -317,6 +335,7 @@ static const struct drm_bridge_funcs tidss_oldi_bridge_funcs = {
>  	.atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
>  	.atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
>  	.atomic_reset = drm_atomic_helper_bridge_reset,
> +	.mode_valid = tidss_oldi_mode_valid,
>  };
>  
>  static int get_oldi_mode(struct device_node *oldi_tx, int *companion_instance)
> @@ -430,6 +449,7 @@ void tidss_oldi_deinit(struct tidss_device *tidss)
>  	for (int i = 0; i < tidss->num_oldis; i++) {
>  		if (tidss->oldis[i]) {
>  			drm_bridge_remove(&tidss->oldis[i]->bridge);
> +			tidss->is_ext_vp_clk[tidss->oldis[i]->parent_vp] = false;
>  			tidss->oldis[i] = NULL;
>  		}
>  	}
> @@ -580,6 +600,7 @@ int tidss_oldi_init(struct tidss_device *tidss)
>  		oldi->bridge.timings = &default_tidss_oldi_timings;
>  
>  		tidss->oldis[tidss->num_oldis++] = oldi;
> +		tidss->is_ext_vp_clk[oldi->parent_vp] = true;
>  		oldi->tidss = tidss;
>  
>  		drm_bridge_add(&oldi->bridge);