linux-kernel - Re: [PATCH v6 3/3] drm/tidss: oldi: Add atomic

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Message-ID: <4f0a00d9-4edc-4114-aca6-70d6bb654767@ti.com>
Date: Mon, 15 Sep 2025 14:25:27 +0530
From: Swamil Jain <s-jain1@...com>
To: Maxime Ripard <mripard@...nel.org>
CC: <jyri.sarha@....fi>, <tomi.valkeinen@...asonboard.com>,
        <maarten.lankhorst@...ux.intel.com>, <tzimmermann@...e.de>,
        <airlied@...il.com>, <simona@...ll.ch>, <aradhya.bhatia@...ux.dev>,
        <h-shenoy@...com>, <devarsht@...com>, <vigneshr@...com>,
        <praneeth@...com>, <u-kumar1@...com>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 3/3] drm/tidss: oldi: Add atomic_check hook for oldi
 bridge

Hi,

On 9/15/25 13:27, Maxime Ripard wrote:
> On Thu, Sep 11, 2025 at 04:37:15PM +0530, Swamil Jain wrote:
>> From: Jayesh Choudhary <j-choudhary@...com>
>>
>> Since OLDI consumes DSS VP clock directly as serial clock, mode_valid()
>> check cannot be performed in tidss driver which should be checked
>> in OLDI driver.
>>
>> 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_oldi.c | 21 +++++++++++++++++++++
>>   1 file changed, 21 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/tidss/tidss_oldi.c b/drivers/gpu/drm/tidss/tidss_oldi.c
>> index 7ecbb2c3d0a2..ada691839ef3 100644
>> --- a/drivers/gpu/drm/tidss/tidss_oldi.c
>> +++ b/drivers/gpu/drm/tidss/tidss_oldi.c
>> @@ -309,6 +309,26 @@ static u32 *tidss_oldi_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
>>   	return input_fmts;
>>   }
>>   
>> +static int tidss_oldi_atomic_check(struct drm_bridge *bridge,
>> +				   struct drm_bridge_state *bridge_state,
>> +				   struct drm_crtc_state *crtc_state,
>> +				   struct drm_connector_state *conn_state)
>> +{
>> +	struct tidss_oldi *oldi = drm_bridge_to_tidss_oldi(bridge);
>> +	struct drm_display_mode *adjusted_mode;
>> +	unsigned long round_clock;
>> +
>> +	adjusted_mode = &crtc_state->adjusted_mode;
>> +	round_clock = clk_round_rate(oldi->serial, adjusted_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(adjusted_mode->clock * 7 * 1000, round_clock) > 5)
>> +		return -EINVAL;
>> +	return 0;
>> +}
>> +
> 
> If you're introducing that check to tidss, please use .5% like everyone
> else. I understand that you don't want to change tilcdc to avoid any
> regression, but that's not the case here
>
This is just to make the tolerance check consistent for mode validation 
and setting clock rate. This patch isn't introducing anything new, we 
are following this as dispc_vp_set_clk_rate() and 
tidss_oldi_set_serial_clk() are already checking for 5% tolerance while 
setting clock. To remove/modify, this needs extensive testing with other 
K3 and K2G SoCs and can be handled as a separate patch.

Regards,
Swamil

> Maxime