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

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Message-ID: <20250915-affable-melodic-antelope-db56c2@penduick>
Date: Mon, 15 Sep 2025 14:24:30 +0200
From: Maxime Ripard <mripard@...nel.org>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc: Swamil Jain <s-jain1@...com>, jyri.sarha@....fi, 
	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

On Mon, Sep 15, 2025 at 01:17:52PM +0300, Tomi Valkeinen wrote:
> Hi,
> 
> On 15/09/2025 11:55, Swamil Jain wrote:
> > 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.
> 
> I'd like to switch to 0.5%, but as Swamil said, I think it's better to
> do it on top.

Yeah, sorry, I thought it was a new thing.

Maxime

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