Re: [PATCH v2] thunderbolt: Explicitly enable lane adapter hotplug events at startup

Limonciello, Mario
2022-09-23T16:08:43Z

On 9/23/2022 04:16, Mika Westerberg wrote:
> Hi Mario,
>
> On Thu, Sep 22, 2022 at 11:07:29AM -0500, Mario Limonciello wrote:
>> Software that has run before the USB4 CM in Linux runs may have disabled
>> hotplug events for a given lane adapter.
>>
>> Other CMs such as that one distributed with Windows 11 will enable hotplug
>> events. Do the same thing in the Linux CM which fixes hotplug events on
>> "AMD Pink Sardine".
>>
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>> v1->v2:
>> * Only send second patch as first was merged already
>> * s/usb4_enable_hotplug/usb4_port_hotplug_enable/
>> * Clarify intended users in documentation comment
>> * Only call for lane adapters
>> * Add stable tag
>>
>> drivers/thunderbolt/switch.c | 4 ++++
>> drivers/thunderbolt/tb.h | 1 +
>> drivers/thunderbolt/tb_regs.h | 1 +
>> drivers/thunderbolt/usb4.c | 20 ++++++++++++++++++++
>> 4 files changed, 26 insertions(+)
>>
>> diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
>> index 77d7f07ca075..3213239d12c8 100644
>> --- a/drivers/thunderbolt/switch.c
>> +++ b/drivers/thunderbolt/switch.c
>> @@ -778,6 +778,10 @@ static int tb_init_port(struct tb_port *port)
>>
>> if (!tb_port_read(port, &hop, TB_CFG_HOPS, 0, 2))
>> port->ctl_credits = hop.initial_credits;
>> +
>> + res = usb4_port_hotplug_enable(port);
>> + if (res)
>
> I think this does not belong here in tb_init_port(). This is called from
> both FW and SW CM paths and we don't want to confuse the FW CM more than
> necessary ;-)
>
> So instead I think this should be added to tb_plug_events_active().
>

The problem with that location is that tb_plug_events_active() is called
from tb_switch_configure() which is before tb_switch_add() is called.
tb_switch_add() calls tb_init_port() which reads port->config for the
first time.

So if this is only to be called in tb_switch_configure() it means
reading port->config "earlier" too.

So it definitely needs to be called in tb_init_port() or a later
function but before the device is announced to satisfy only running on
the appropriate port types.

tb_init_port() or tb_switch_add feels like the right place to me. How
about leaving it where it is but guarding with a "if
(!tb_switch_is_icm())" to avoid the risk to the FW CM case?

> Otherwise looks good to me.
>
>> + return res;
>> }
>> if (!port->ctl_credits)
>> port->ctl_credits = 2;
>> diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
>> index 5db76de40cc1..332159f984fc 100644
>> --- a/drivers/thunderbolt/tb.h
>> +++ b/drivers/thunderbolt/tb.h
>> @@ -1174,6 +1174,7 @@ int usb4_switch_add_ports(struct tb_switch *sw);
>> void usb4_switch_remove_ports(struct tb_switch *sw);
>>
>> int usb4_port_unlock(struct tb_port *port);
>> +int usb4_port_hotplug_enable(struct tb_port *port);
>> int usb4_port_configure(struct tb_port *port);
>> void usb4_port_unconfigure(struct tb_port *port);
>> int usb4_port_configure_xdomain(struct tb_port *port);
>> diff --git a/drivers/thunderbolt/tb_regs.h b/drivers/thunderbolt/tb_regs.h
>> index 166054110388..bbe38b2d9057 100644
>> --- a/drivers/thunderbolt/tb_regs.h
>> +++ b/drivers/thunderbolt/tb_regs.h
>> @@ -308,6 +308,7 @@ struct tb_regs_port_header {
>> #define ADP_CS_5 0x05
>> #define ADP_CS_5_LCA_MASK GENMASK(28, 22)
>> #define ADP_CS_5_LCA_SHIFT 22
>> +#define ADP_CS_5_DHP BIT(31)
>>
>> /* TMU adapter registers */
>> #define TMU_ADP_CS_3 0x03
>> diff --git a/drivers/thunderbolt/usb4.c b/drivers/thunderbolt/usb4.c
>> index 3a2e7126db9d..f0b5a8f1ed3a 100644
>> --- a/drivers/thunderbolt/usb4.c
>> +++ b/drivers/thunderbolt/usb4.c
>> @@ -1046,6 +1046,26 @@ int usb4_port_unlock(struct tb_port *port)
>> return tb_port_write(port, &val, TB_CFG_PORT, ADP_CS_4, 1);
>> }
>>
>> +/**
>> + * usb4_port_hotplug_enable() - Enables hotplug for a port
>> + * @port: USB4 port to operate on
>> + *
>> + * Enables hot plug events on a given port. This is only intended
>> + * to be used on lane, DP-IN, and DP-OUT adapters.
>> + */
>> +int usb4_port_hotplug_enable(struct tb_port *port)
>> +{
>> + int ret;
>> + u32 val;
>> +
>> + ret = tb_port_read(port, &val, TB_CFG_PORT, ADP_CS_5, 1);
>> + if (ret)
>> + return ret;
>> +
>> + val &= ~ADP_CS_5_DHP;
>> + return tb_port_write(port, &val, TB_CFG_PORT, ADP_CS_5, 1);
>> +}
>> +
>> static int usb4_port_set_configured(struct tb_port *port, bool configured)
>> {
>> int ret;
>> --
>> 2.34.1