Re: [PATCH 5/5] thunderbolt: Change TMU mode to Hifi-Uni once DP tunneled

[Mika Westerberg <mika.westerberg@linux.intel.com>]

On Sun, May 01, 2022 at 11:33:21PM +0300, Gil Fine wrote:
> Here we configure TMU mode to Hifi-Uni once DP tunnel is created.

DisplayPort (at least use that in the $subject).

> This is due to accuracy requirement for DP tunneling as appears in
> CM guide 1.0, section 7.3.2
> Due to Intel HW limitation, once we changed the TMU mode to Hifi-Uni

HW -> hardware

HiFi uni-directional

> (when DP is tunnel exists), we don't change TMU mode back to Normal-Uni,

normal un-idirectional

> even if DP tunnel is teared-down later.

torn down

> 
> Signed-off-by: Gil Fine <gil.fine@intel.com>
> ---
>  drivers/thunderbolt/tb.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)
> 
> diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
> index 05a084e3e9f6..efe53d221ca8 100644
> --- a/drivers/thunderbolt/tb.c
> +++ b/drivers/thunderbolt/tb.c
> @@ -50,6 +50,8 @@ struct tb_hotplug_event {
>  };
>  
>  static void tb_handle_hotplug(struct work_struct *work);
> +static int tb_enable_tmu_1st_child(struct tb *tb,
> +				   enum tb_switch_tmu_rate rate);
>  
>  static void tb_queue_hotplug(struct tb *tb, u64 route, u8 port, bool unplug)
>  {
> @@ -118,6 +120,13 @@ static void tb_switch_discover_tunnels(struct tb_switch *sw,
>  		switch (port->config.type) {
>  		case TB_TYPE_DP_HDMI_IN:
>  			tunnel = tb_tunnel_discover_dp(tb, port, alloc_hopids);
> +			/*
> +			 * In case of DP tunnel exists, change TMU mode to
> +			 * HiFi for CL0s to work.
> +			 */
> +			if (tunnel)
> +				tb_enable_tmu_1st_child(tb,
> +						TB_SWITCH_TMU_RATE_HIFI);
>  			break;
>  
>  		case TB_TYPE_PCIE_DOWN:
> @@ -235,6 +244,31 @@ static int tb_enable_tmu(struct tb_switch *sw)
>  	return tb_switch_tmu_enable(sw);
>  }
>  
> +/*
> + * Once a DP tunnel exists in the domain, we set the TMU mode so that
> + * it meets the accuracy requirements and also enables CLx entry (CL0s).
> + * We set the TMU mode of the first depth router(s) for CL0s to work.
> + */
> +static int tb_enable_tmu_1st_child(struct tb *tb, enum tb_switch_tmu_rate rate)
> +{
> +	struct tb_switch *root_sw = tb->root_switch;
> +	struct tb_port *port;
> +
> +	tb_switch_for_each_port(root_sw, port) {

Can't you use device_for_each_child() here?

> +		struct tb_switch *sw;
> +		int ret;
> +
> +		if (!tb_port_has_remote(port) || !tb_port_is_null(port))
> +			continue;
> +		sw = port->remote->sw;
> +		tb_switch_tmu_configure(sw, rate, tb_switch_is_clx_enabled(sw));
> +		if (tb_switch_tmu_enable(sw))
> +			tb_dbg(tb, "Fail switching TMU to HiFi for 1st depth router %d\n", ret);
> +	}
> +
> +	return 0;
> +}
> +
>  /**
>   * tb_find_unused_port() - return the first inactive port on @sw
>   * @sw: Switch to find the port on
> @@ -981,6 +1015,12 @@ static void tb_tunnel_dp(struct tb *tb)
>  
>  	list_add_tail(&tunnel->list, &tcm->tunnel_list);
>  	tb_reclaim_usb3_bandwidth(tb, in, out);
> +	/*
> +	 * In case of DP tunnel exists, change TMU mode to
> +	 * HiFi for CL0s to work.
> +	 */
> +	tb_enable_tmu_1st_child(tb, TB_SWITCH_TMU_RATE_HIFI);
> +
>  	return;
>  
>  err_free:
> -- 
> 2.17.1