Re: [PATCH 08/13] drm/i915/tc: Refactor TC-cold block/unblock helpers

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On Tue, 2021-09-21 at 03:23 +0300, Imre Deak wrote:
> A follow-up change will select the TC-cold blocking power domain based
> on the TypeC mode, prepare for that here.
> 
> Also bring intel_tc_cold_requires_aux_pw() earlier to its logical place
> for readability.
> 
> No functional change.
> 
> Cc: José Roberto de Souza <jose.souza@xxxxxxxxx>
> Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
> ---
>  .../drm/i915/display/intel_display_types.h    |  2 +
>  drivers/gpu/drm/i915/display/intel_tc.c       | 63 +++++++++++--------
>  2 files changed, 39 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index e9e806d90eec4..08a73ffded957 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -1663,8 +1663,10 @@ struct intel_digital_port {
>  	enum intel_display_power_domain ddi_io_power_domain;
>  	intel_wakeref_t ddi_io_wakeref;
>  	intel_wakeref_t aux_wakeref;
> +
>  	struct mutex tc_lock;	/* protects the TypeC port mode */
>  	intel_wakeref_t tc_lock_wakeref;
> +	enum intel_display_power_domain tc_lock_power_domain;
>  	int tc_link_refcount;
>  	bool tc_legacy_port:1;
>  	char tc_port_name[8];
> diff --git a/drivers/gpu/drm/i915/display/intel_tc.c b/drivers/gpu/drm/i915/display/intel_tc.c
> index 77b16a7c43466..24d2dc2e19a7d 100644
> --- a/drivers/gpu/drm/i915/display/intel_tc.c
> +++ b/drivers/gpu/drm/i915/display/intel_tc.c
> @@ -48,8 +48,16 @@ bool intel_tc_port_in_legacy_mode(struct intel_digital_port *dig_port)
>  	return intel_tc_port_in_mode(dig_port, TC_PORT_LEGACY);
>  }
>  
> +bool intel_tc_cold_requires_aux_pw(struct intel_digital_port *dig_port)
> +{
> +	struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
> +
> +	return (DISPLAY_VER(i915) == 11 && dig_port->tc_legacy_port) ||
> +		IS_ALDERLAKE_P(i915);
> +}
> +
>  static enum intel_display_power_domain
> -tc_cold_get_power_domain(struct intel_digital_port *dig_port)
> +tc_cold_get_power_domain(struct intel_digital_port *dig_port, enum tc_port_mode mode)
>  {
>  	if (intel_tc_cold_requires_aux_pw(dig_port))
>  		return intel_legacy_aux_to_power_domain(dig_port->aux_ch);
> @@ -58,23 +66,30 @@ tc_cold_get_power_domain(struct intel_digital_port *dig_port)
>  }
>  
>  static intel_wakeref_t
> -tc_cold_block(struct intel_digital_port *dig_port)
> +tc_cold_block_in_mode(struct intel_digital_port *dig_port, enum tc_port_mode mode,
> +		      enum intel_display_power_domain *domain)
>  {
>  	struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
> -	enum intel_display_power_domain domain;
>  
>  	if (DISPLAY_VER(i915) == 11 && !dig_port->tc_legacy_port)
>  		return 0;
>  
> -	domain = tc_cold_get_power_domain(dig_port);
> -	return intel_display_power_get(i915, domain);
> +	*domain = tc_cold_get_power_domain(dig_port, mode);

I see problems with this approach.
If there is a TC alt-mode is connected and current software state is TBT or disconnected it will not get the power domain to exit TC cold, what could
case invalid reads of registers.

>From the next patch commit message: 'For the ADL-P TBT mode the spec doesn't require blocking TC-cold by
using the legacy AUX power domain'.

It is not required for TBT but when there is nothing connected, hardware is not in TBT mode so it can still get into TC cold.

> +
> +	return intel_display_power_get(i915, *domain);
> +}
> +
> +static intel_wakeref_t
> +tc_cold_block(struct intel_digital_port *dig_port, enum intel_display_power_domain *domain)
> +{
> +	return tc_cold_block_in_mode(dig_port, dig_port->tc_mode, domain);
>  }
>  
>  static void
> -tc_cold_unblock(struct intel_digital_port *dig_port, intel_wakeref_t wakeref)
> +tc_cold_unblock(struct intel_digital_port *dig_port, enum intel_display_power_domain domain,
> +		intel_wakeref_t wakeref)
>  {
>  	struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
> -	enum intel_display_power_domain domain;
>  
>  	/*
>  	 * wakeref == -1, means some error happened saving save_depot_stack but
> @@ -84,8 +99,7 @@ tc_cold_unblock(struct intel_digital_port *dig_port, intel_wakeref_t wakeref)
>  	if (wakeref == 0)
>  		return;
>  
> -	domain = tc_cold_get_power_domain(dig_port);
> -	intel_display_power_put_async(i915, domain, wakeref);
> +	intel_display_power_put(i915, domain, wakeref);
>  }
>  
>  static void
> @@ -98,7 +112,8 @@ assert_tc_cold_blocked(struct intel_digital_port *dig_port)
>  		return;
>  
>  	enabled = intel_display_power_is_enabled(i915,
> -						 tc_cold_get_power_domain(dig_port));
> +						 tc_cold_get_power_domain(dig_port,
> +									  dig_port->tc_mode));
>  	drm_WARN_ON(&i915->drm, !enabled);
>  }
>  
> @@ -634,7 +649,8 @@ void intel_tc_port_sanitize(struct intel_digital_port *dig_port)
>  
>  	drm_WARN_ON(&i915->drm, dig_port->tc_mode != TC_PORT_DISCONNECTED);
>  	if (active_links) {
> -		intel_wakeref_t tc_cold_wref = tc_cold_block(dig_port);
> +		enum intel_display_power_domain domain;
> +		intel_wakeref_t tc_cold_wref = tc_cold_block(dig_port, &domain);
>  
>  		dig_port->tc_mode = intel_tc_port_get_current_mode(dig_port);
>  
> @@ -644,7 +660,7 @@ void intel_tc_port_sanitize(struct intel_digital_port *dig_port)
>  				    dig_port->tc_port_name, active_links);
>  		intel_tc_port_link_init_refcount(dig_port, active_links);
>  
> -		tc_cold_unblock(dig_port, tc_cold_wref);
> +		tc_cold_unblock(dig_port, domain, tc_cold_wref);
>  	}
>  
>  	drm_dbg_kms(&i915->drm, "Port %s: sanitize mode (%s)\n",
> @@ -673,15 +689,16 @@ bool intel_tc_port_connected(struct intel_encoder *encoder)
>  {
>  	struct intel_digital_port *dig_port = enc_to_dig_port(encoder);
>  	bool is_connected;
> +	enum intel_display_power_domain domain;
>  	intel_wakeref_t tc_cold_wref;
>  
>  	intel_tc_port_lock(dig_port);
> -	tc_cold_wref = tc_cold_block(dig_port);
> +	tc_cold_wref = tc_cold_block(dig_port, &domain);
>  
>  	is_connected = tc_port_live_status_mask(dig_port) &
>  		       BIT(dig_port->tc_mode);
>  
> -	tc_cold_unblock(dig_port, tc_cold_wref);
> +	tc_cold_unblock(dig_port, domain, tc_cold_wref);
>  	intel_tc_port_unlock(dig_port);
>  
>  	return is_connected;
> @@ -698,15 +715,16 @@ static void __intel_tc_port_lock(struct intel_digital_port *dig_port,
>  	mutex_lock(&dig_port->tc_lock);
>  
>  	if (!dig_port->tc_link_refcount) {
> +		enum intel_display_power_domain domain;
>  		intel_wakeref_t tc_cold_wref;
>  
> -		tc_cold_wref = tc_cold_block(dig_port);
> +		tc_cold_wref = tc_cold_block(dig_port, &domain);
>  
>  		if (force_disconnect || intel_tc_port_needs_reset(dig_port))
>  			intel_tc_port_reset_mode(dig_port, required_lanes,
>  						 force_disconnect);
>  
> -		tc_cold_unblock(dig_port, tc_cold_wref);
> +		tc_cold_unblock(dig_port, domain, tc_cold_wref);
>  	}
>  
>  	drm_WARN_ON(&i915->drm, dig_port->tc_mode == TC_PORT_DISCONNECTED);
> @@ -775,6 +793,7 @@ void intel_tc_port_put_link(struct intel_digital_port *dig_port)
>  static bool
>  tc_has_modular_fia(struct drm_i915_private *i915, struct intel_digital_port *dig_port)
>  {
> +	enum intel_display_power_domain domain;
>  	intel_wakeref_t wakeref;
>  	u32 val;
>  
> @@ -782,9 +801,9 @@ tc_has_modular_fia(struct drm_i915_private *i915, struct intel_digital_port *dig
>  		return false;
>  
>  	mutex_lock(&dig_port->tc_lock);
> -	wakeref = tc_cold_block(dig_port);
> +	wakeref = tc_cold_block(dig_port, &domain);
>  	val = intel_uncore_read(&i915->uncore, PORT_TX_DFLEXDPSP(FIA1));
> -	tc_cold_unblock(dig_port, wakeref);
> +	tc_cold_unblock(dig_port, domain, wakeref);
>  	mutex_unlock(&dig_port->tc_lock);
>  
>  	drm_WARN_ON(&i915->drm, val == 0xffffffff);
> @@ -829,11 +848,3 @@ void intel_tc_port_init(struct intel_digital_port *dig_port, bool is_legacy)
>  	dig_port->tc_link_refcount = 0;
>  	tc_port_load_fia_params(i915, dig_port);
>  }
> -
> -bool intel_tc_cold_requires_aux_pw(struct intel_digital_port *dig_port)
> -{
> -	struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
> -
> -	return (DISPLAY_VER(i915) == 11 && dig_port->tc_legacy_port) ||
> -		IS_ALDERLAKE_P(i915);
> -}





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