Re: [PATCH v2 10/10] drm/bridge: tc358775: Configure hs_rate and lp_rate

[Michael Walle <mwalle@kernel.org>]

> The hs_rate and lp_rate may be used by the dsi host for timing
> calculations. The tc358775 has a maximum bit rate of 1 Gbps/lane,
> tc358765 has maximurate of 800 Mbps per lane.
> 
> Signed-off-by: Tony Lindgren <tony@atomide.com>
> ---
>  drivers/gpu/drm/bridge/tc358775.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/tc358775.c b/drivers/gpu/drm/bridge/tc358775.c
> --- a/drivers/gpu/drm/bridge/tc358775.c
> +++ b/drivers/gpu/drm/bridge/tc358775.c
> @@ -636,6 +636,11 @@ static int tc_attach_host(struct tc_data *tc)
>  	dsi->format = MIPI_DSI_FMT_RGB888;
>  	dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST |
>  		MIPI_DSI_MODE_LPM;
> +	if (tc->type == TC358765)
> +		dsi->hs_rate = 800000000;

It's not clear to me whether this is the data rate or the frequency. From
the kernel doc:

 * @hs_rate: maximum lane frequency for high speed mode in hertz, this should
 * be set to the real limits of the hardware, zero is only accepted for
 * legacy drivers

The tc358775 datasheet lists 1Gbps per lane, which corresponds to a 500MHz DSI
clock frequency. Not sure how that would correspond to the "maximum lane
frequency" above. I guess the wording of the comment is just misleading and
the value is the data rate of the lane.

> +	else
> +		dsi->hs_rate = 1000000000;
> +	dsi->lp_rate = 10000000;

That I didn't found in the datasheet. Just a T_min_rx (minimum pulse width
response) which is 20ns. But there are no more details on this.

-michael