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Message-ID: <486f2a39-90bd-493f-89ad-4f7060fc8158@ti.com>
Date: Mon, 3 Nov 2025 21:48:05 +0530
From: Swamil Jain <s-jain1@...com>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
<aradhya.bhatia@...ux.dev>, <devarsht@...com>, <mripard@...nel.org>,
<jyri.sarha@....fi>, <maarten.lankhorst@...ux.intel.com>, <simona@...ll.ch>,
<airlied@...il.com>, <tzimmermann@...e.de>, <h-shenoy@...com>
CC: <praneeth@...com>, <u-kumar1@...com>, <vigneshr@...com>,
<dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND PATCH v7 2/2] drm/tidss: Move OLDI mode validation to
OLDI bridge mode_valid hook
Hi Tomi,
On 03-11-2025 13:35, Tomi Valkeinen wrote:
> Hi,
>
> On 28/10/2025 05:39, Swamil Jain wrote:
>> From: Jayesh Choudhary <j-choudhary@...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@...nel.org>
>> Reviewed-by: Devarsh Thakkar <devarsht@...com>
>> Signed-off-by: Jayesh Choudhary <j-choudhary@...com>
>> Signed-off-by: Swamil Jain <s-jain1@...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.
Sure, will add and respin. Thanks for reviewing.
Regards,
Swamil>
> Reviewed-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.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);
>
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