G'day Mika,

I'm sending you two dmesg because with that patch applied, a warm boot 
(as in reboot) comes up with all 3 heads, but a cold boot only has the 
two. I thought that was odd, so I reproduced it a couple of times just 
to check.

So cold boot is dmesg.07 and warm boot is dmesg.06. If I cold boot I get 
2 displays. A reboot from there results in all 3.

I compiled, installed and rebooted into all 3 heads (which somewhat 
threw me, so I tried it a couple of times).

So that patch certainly made a difference. Timing/race issue?

Regards,
Brad

On 3/9/19 6:13 pm, Mika Westerberg wrote:
> Hi Brad,
> 
> On Thu, Aug 29, 2019 at 12:27:08AM +0800, Brad Campbell wrote:
>> It wouldn't surprise me if the firmware was doing something funky. It was
>> one of the first Thunderbolt equipped models and the support docs explicitly
>> say only one Thunderbolt display in Windows and two in later versions of
>> OSX. It almost needs a quirk to say "firmware does something we don't like,
>> reset the controller and re-discover from scratch".
>>
>> Anyway, I'm not in any hurry. It doesn't get rebooted often and it's not in
>> any way preventing me using the machine. In fact, upgrading the third head
>> from an old 24" 1920x1200 to the second Thunderbolt display has been
>> invaluable.
> 
> Can you apply the below patch and then boot with two monitors connected?
> Then send me the dmesg. It does not fix anything but should log a bit
> more.
> 
> diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
> index 1f7a9e1cc09c..28a72336558a 100644
> --- a/drivers/thunderbolt/tb.c
> +++ b/drivers/thunderbolt/tb.c
> @@ -313,8 +313,10 @@ static struct tb_port *tb_find_unused_port(struct tb_switch *sw,
>   			continue;
>   		if (!sw->ports[i].cap_adap)
>   			continue;
> -		if (tb_port_is_enabled(&sw->ports[i]))
> +		if (tb_port_is_enabled(&sw->ports[i])) {
> +			tb_port_dbg(&sw->ports[i], "this already enabled\n");
>   			continue;
> +		}
>   		return &sw->ports[i];
>   	}
>   	return NULL;
> @@ -365,16 +367,25 @@ static int tb_tunnel_dp(struct tb *tb, struct tb_port *out)
>   	struct tb_tunnel *tunnel;
>   	struct tb_port *in;
>   
> -	if (tb_port_is_enabled(out))
> +	tb_port_dbg(out, "trying to tunnel DP\n");
> +
> +	if (tb_port_is_enabled(out)) {
> +		tb_port_dbg(out, "DP OUT port already enabled\n");
>   		return 0;
> +	}
> +
> +	tb_port_dbg(out, "finding free DP IN port\n");
>   
>   	do {
>   		sw = tb_to_switch(sw->dev.parent);
>   		if (!sw)
>   			return 0;
> +		tb_sw_dbg(sw, "finding available DP IN\n");
>   		in = tb_find_unused_port(sw, TB_TYPE_DP_HDMI_IN);
>   	} while (!in);
>   
> +	tb_port_dbg(in, "found DP IN\n");
> +
>   	tunnel = tb_tunnel_alloc_dp(tb, in, out);
>   	if (!tunnel) {
>   		tb_port_dbg(out, "DP tunnel allocation failed\n");
> diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
> index 5a99234826e7..93c2c965bdde 100644
> --- a/drivers/thunderbolt/tunnel.c
> +++ b/drivers/thunderbolt/tunnel.c
> @@ -351,9 +351,23 @@ struct tb_tunnel *tb_tunnel_discover_dp(struct tb *tb, struct tb_port *in)
>   	struct tb_tunnel *tunnel;
>   	struct tb_port *port;
>   	struct tb_path *path;
> +	u32 data[2];
> +	int ret;
> +
> +	tb_port_dbg(in, "start DP discover\n");
>   
> -	if (!tb_dp_port_is_enabled(in))
> +	if (!tb_dp_port_is_enabled(in)) {
> +		tb_port_dbg(in, "DP port enabled\n");
>   		return NULL;
> +	}
> +
> +	ret = tb_port_read(in, data, TB_CFG_PORT, in->cap_adap,
> +			   ARRAY_SIZE(data));
> +	if (ret)
> +		return NULL;
> +
> +	tb_port_dbg(in, "data[0]=0x%08x\n", data[0]);
> +	tb_port_dbg(in, "data[1]=0x%08x\n", data[1]);
>   
>   	tunnel = tb_tunnel_alloc(tb, 3, TB_TUNNEL_DP);
>   	if (!tunnel)
>