[PATCH iwl-net v1 0/4] igc bug fixes related to qbv_count usage

[PATCH iwl-net v1 0/4] igc bug fixes related to qbv_count usage

[Faizal Rahim]

These igc bug fixes are sent as a patch series because:

1. The patch "igc: Remove unused qbv_count" has dependency on:
   "igc: Fix qbv_config_change_errors logics" 
   "igc: Fix reset adapter logics when tx mode change"

   These two patches remove the reliance on using the qbv_count field.
 
2. The patch "igc: Fix qbv tx latency by setting gtxoffset" reuse the
   function igc_tsn_will_tx_mode_change() created in the patch: 
   "igc: Fix reset adapter logics when tx mode change"

Faizal Rahim (4):
  igc: Fix qbv_config_change_errors logics
  igc: Fix reset adapter logics when tx mode change
  igc: Remove unused qbv_count
  igc: Fix qbv tx latency by setting gtxoffset

 drivers/net/ethernet/intel/igc/igc.h      |  1 -
 drivers/net/ethernet/intel/igc/igc_main.c |  9 +++--
 drivers/net/ethernet/intel/igc/igc_tsn.c  | 49 ++++++++++++++++-------
 drivers/net/ethernet/intel/igc/igc_tsn.h  |  1 +
 4 files changed, 42 insertions(+), 18 deletions(-)

-- 
2.25.1

[PATCH iwl-net v1 1/4] igc: Fix qbv_config_change_errors logics

[Faizal Rahim]

When user issues these cmds:
1. Either a) or b)
   a) mqprio with hardware offload disabled
   b) taprio with txtime-assist feature enabled
2. etf
3. tc qdisc delete
4. taprio with base time in the past

At step 4, qbv_config_change_errors wrongly increased by 1.

Excerpt from IEEE 802.1Q-2018 8.6.9.3.1:
"If AdminBaseTime specifies a time in the past, and the current schedule
is running, then: Increment ConfigChangeError counter"

qbv_config_change_errors should only increase if base time is in the past
and no taprio is active. In user perspective, taprio was not active when
first triggered at step 4. However, i225/6 reuses qbv for etf, so qbv is
enabled with a dummy schedule at step 2 where it enters
igc_tsn_enable_offload() and qbv_count got incremented to 1. At step 4, it
enters igc_tsn_enable_offload() again, qbv_count is incremented to 2.
Because taprio is running, tc_setup_type is TC_SETUP_QDISC_ETF and
qbv_count > 1, qbv_config_change_errors value got incremented.

This issue happens due to reliance on qbv_count field where a non-zero
value indicates that taprio is running. But qbv_count increases
regardless if taprio is triggered by user or by other tsn feature. It does
not align with qbv_config_change_errors expectation where it is only
concerned with taprio triggered by user.

Fixing this by relocating the qbv_config_change_errors logic to
igc_save_qbv_schedule(), eliminating reliance on qbv_count and its
inaccuracies from i225/6's multiple uses of qbv feature for other TSN
features.

The new function created: igc_tsn_is_taprio_activated_by_user() uses
taprio_offload_enable field to indicate that the current running taprio
was triggered by user, instead of triggered by non-qbv feature like etf.

Fixes: ae4fe4698300 ("igc: Add qbv_config_change_errors counter")
Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>
---
 drivers/net/ethernet/intel/igc/igc_main.c |  8 ++++++--
 drivers/net/ethernet/intel/igc/igc_tsn.c  | 19 +++++++++++--------
 drivers/net/ethernet/intel/igc/igc_tsn.h  |  1 +
 3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 305e05294a26..0f8a5ad940ec 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -6334,12 +6334,16 @@ static int igc_save_qbv_schedule(struct igc_adapter *adapter,
 	if (!validate_schedule(adapter, qopt))
 		return -EINVAL;
 
+	igc_ptp_read(adapter, &now);
+
+	if (igc_tsn_is_taprio_activated_by_user(adapter) &&
+	    is_base_time_past(qopt->base_time, &now))
+		adapter->qbv_config_change_errors++;
+
 	adapter->cycle_time = qopt->cycle_time;
 	adapter->base_time = qopt->base_time;
 	adapter->taprio_offload_enable = true;
 
-	igc_ptp_read(adapter, &now);
-
 	for (n = 0; n < qopt->num_entries; n++) {
 		struct tc_taprio_sched_entry *e = &qopt->entries[n];
 
diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
index 22cefb1eeedf..02dd41aff634 100644
--- a/drivers/net/ethernet/intel/igc/igc_tsn.c
+++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
@@ -78,6 +78,17 @@ void igc_tsn_adjust_txtime_offset(struct igc_adapter *adapter)
 	wr32(IGC_GTXOFFSET, txoffset);
 }
 
+bool igc_tsn_is_taprio_activated_by_user(struct igc_adapter *adapter)
+{
+	struct igc_hw *hw = &adapter->hw;
+
+	if ((rd32(IGC_BASET_H) || rd32(IGC_BASET_L)) &&
+	    adapter->taprio_offload_enable)
+		return true;
+	else
+		return false;
+}
+
 /* Returns the TSN specific registers to their default values after
  * the adapter is reset.
  */
@@ -262,14 +273,6 @@ static int igc_tsn_enable_offload(struct igc_adapter *adapter)
 		s64 n = div64_s64(ktime_sub_ns(systim, base_time), cycle);
 
 		base_time = ktime_add_ns(base_time, (n + 1) * cycle);
-
-		/* Increase the counter if scheduling into the past while
-		 * Gate Control List (GCL) is running.
-		 */
-		if ((rd32(IGC_BASET_H) || rd32(IGC_BASET_L)) &&
-		    (adapter->tc_setup_type == TC_SETUP_QDISC_TAPRIO) &&
-		    (adapter->qbv_count > 1))
-			adapter->qbv_config_change_errors++;
 	} else {
 		if (igc_is_device_id_i226(hw)) {
 			ktime_t adjust_time, expires_time;
diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.h b/drivers/net/ethernet/intel/igc/igc_tsn.h
index b53e6af560b7..98ec845a86bf 100644
--- a/drivers/net/ethernet/intel/igc/igc_tsn.h
+++ b/drivers/net/ethernet/intel/igc/igc_tsn.h
@@ -7,5 +7,6 @@
 int igc_tsn_offload_apply(struct igc_adapter *adapter);
 int igc_tsn_reset(struct igc_adapter *adapter);
 void igc_tsn_adjust_txtime_offset(struct igc_adapter *adapter);
+bool igc_tsn_is_taprio_activated_by_user(struct igc_adapter *adapter);
 
 #endif /* _IGC_BASE_H */
-- 
2.25.1

[PATCH iwl-net v1 2/4] igc: Fix reset adapter logics when tx mode change

[Faizal Rahim]

Following the "igc: Fix TX Hang issue when QBV Gate is close" changes,
remaining issues with the reset adapter logic in igc_tsn_offload_apply()
have been observed:

1. The reset adapter logics for i225 and i226 differ, although they should
   be the same according to the guidelines in I225/6 HW Design Section
   7.5.2.1 on software initialization during tx mode changes.
2. The i225 resets adapter every time, even though tx mode doesn't change.
   This occurs solely based on the condition  igc_is_device_id_i225() when
   calling schedule_work().
3. i226 doesn't reset adapter for tsn->legacy tx mode changes. It only
   resets adapter for legacy->tsn tx mode transitions.
4. qbv_count introduced in the patch is actually not needed; in this
   context, a non-zero value of qbv_count is used to indicate if tx mode
   was unconditionally set to tsn in igc_tsn_enable_offload(). This could
   be replaced by checking the existing register
   IGC_TQAVCTRL_TRANSMIT_MODE_TSN bit.

This patch resolves all issues and enters schedule_work() to reset the
adapter only when changing tx mode. It also removes reliance on qbv_count.

qbv_count field will be removed in a future patch.

Test ran:

1. Verify reset adapter behaviour in i225/6:
   a) Enrol a new GCL
      Reset adapter observed (tx mode change legacy->tsn)
   b) Enrol a new GCL without deleting qdisc
      No reset adapter observed (tx mode remain tsn->tsn)
   c) Delete qdisc
      Reset adapter observed (tx mode change tsn->legacy)

2. Tested scenario from "igc: Fix TX Hang issue when QBV Gate is closed"
   to confirm it remains resolved.

Fixes: 175c241288c0 ("igc: Fix TX Hang issue when QBV Gate is closed")
Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>
---
 drivers/net/ethernet/intel/igc/igc_tsn.c | 26 +++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
index 02dd41aff634..61f047ebf34d 100644
--- a/drivers/net/ethernet/intel/igc/igc_tsn.c
+++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
@@ -49,6 +49,13 @@ static unsigned int igc_tsn_new_flags(struct igc_adapter *adapter)
 	return new_flags;
 }
 
+static bool igc_tsn_is_tx_mode_in_tsn(struct igc_adapter *adapter)
+{
+	struct igc_hw *hw = &adapter->hw;
+
+	return (bool)(rd32(IGC_TQAVCTRL) & IGC_TQAVCTRL_TRANSMIT_MODE_TSN);
+}
+
 void igc_tsn_adjust_txtime_offset(struct igc_adapter *adapter)
 {
 	struct igc_hw *hw = &adapter->hw;
@@ -334,15 +341,28 @@ int igc_tsn_reset(struct igc_adapter *adapter)
 	return err;
 }
 
+static bool igc_tsn_will_tx_mode_change(struct igc_adapter *adapter)
+{
+	bool any_tsn_enabled = (bool)(igc_tsn_new_flags(adapter) &
+			       IGC_FLAG_TSN_ANY_ENABLED);
+
+	if ((any_tsn_enabled && !igc_tsn_is_tx_mode_in_tsn(adapter)) ||
+	    (!any_tsn_enabled && igc_tsn_is_tx_mode_in_tsn(adapter)))
+		return true;
+	else
+		return false;
+}
+
 int igc_tsn_offload_apply(struct igc_adapter *adapter)
 {
 	struct igc_hw *hw = &adapter->hw;
 
-	/* Per I225/6 HW Design Section 7.5.2.1, transmit mode
-	 * cannot be changed dynamically. Require reset the adapter.
+	/* Per I225/6 HW Design Section 7.5.2.1 guideline, if tx mode change
+	 * from legacy->tsn or tsn->legacy, then reset adapter is needed.
 	 */
 	if (netif_running(adapter->netdev) &&
-	    (igc_is_device_id_i225(hw) || !adapter->qbv_count)) {
+	    (igc_is_device_id_i225(hw) || igc_is_device_id_i226(hw)) &&
+	     igc_tsn_will_tx_mode_change(adapter)) {
 		schedule_work(&adapter->reset_task);
 		return 0;
 	}
-- 
2.25.1

[PATCH iwl-net v1 3/4] igc: Remove unused qbv_count

[Faizal Rahim]

Removing qbv_count which is now obsolete after these 2 patches:
"igc: Fix reset adapter logics when tx mode change"
"igc: Fix qbv_config_change_errors logics"

The variable qbv_count serves to indicate whether Taprio is active or if
the tx mode is in TSN (IGC_TQAVCTRL_TRANSMIT_MODE_TSN). This is due to its
unconditional increment within igc_tsn_enable_offload(), which both runs
Taprio and sets the tx mode to TSN.

Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>
---
 drivers/net/ethernet/intel/igc/igc.h      | 1 -
 drivers/net/ethernet/intel/igc/igc_main.c | 1 -
 drivers/net/ethernet/intel/igc/igc_tsn.c  | 2 --
 3 files changed, 4 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc.h b/drivers/net/ethernet/intel/igc/igc.h
index 8b14c029eda1..5fd0d85f83ac 100644
--- a/drivers/net/ethernet/intel/igc/igc.h
+++ b/drivers/net/ethernet/intel/igc/igc.h
@@ -254,7 +254,6 @@ struct igc_adapter {
 	bool taprio_offload_enable;
 	u32 qbv_config_change_errors;
 	bool qbv_transition;
-	unsigned int qbv_count;
 	/* Access to oper_gate_closed, admin_gate_closed and qbv_transition
 	 * are protected by the qbv_tx_lock.
 	 */
diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 0f8a5ad940ec..e7664bd81505 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -6246,7 +6246,6 @@ static int igc_qbv_clear_schedule(struct igc_adapter *adapter)
 	adapter->cycle_time = NSEC_PER_SEC;
 	adapter->taprio_offload_enable = false;
 	adapter->qbv_config_change_errors = 0;
-	adapter->qbv_count = 0;
 
 	for (i = 0; i < adapter->num_tx_queues; i++) {
 		struct igc_ring *ring = adapter->tx_ring[i];
diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
index 61f047ebf34d..26dbe3442ad1 100644
--- a/drivers/net/ethernet/intel/igc/igc_tsn.c
+++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
@@ -267,8 +267,6 @@ static int igc_tsn_enable_offload(struct igc_adapter *adapter)
 
 	tqavctrl |= IGC_TQAVCTRL_TRANSMIT_MODE_TSN | IGC_TQAVCTRL_ENHANCED_QAV;
 
-	adapter->qbv_count++;
-
 	cycle = adapter->cycle_time;
 	base_time = adapter->base_time;
 
-- 
2.25.1

[PATCH iwl-net v1 4/4] igc: Fix qbv tx latency by setting gtxoffset

[Faizal Rahim]

A large tx latency issue was discovered during testing when only QBV was
enabled. The issue occurs because gtxoffset was not set when QBV is
active, it was only set when launch time is active.

The patch "igc: Correct the launchtime offset" only sets gtxoffset when
the launchtime_enable field is set by the user. Enabling launchtime_enable
ultimately sets the register IGC_TXQCTL_QUEUE_MODE_LAUNCHT (referred to as
LaunchT in the SW user manual).

Section 7.5.2.6 of the IGC i225/6 SW User Manual Rev 1.2.4 states:
"The latency between transmission scheduling (launch time) and the
time the packet is transmitted to the network is listed in Table 7-61."

However, the patch misinterprets the phrase "launch time" in that section
by assuming it specifically refers to the LaunchT register, whereas it
actually denotes the generic term for when a packet is released from the
internal buffer to the MAC transmit logic.

This launch time, as per that section, also implicitly refers to the QBV
gate open time, where a packet waits in the buffer for the QBV gate to
open. Therefore, latency applies whenever QBV is in use. TSN features such
as QBU and QAV reuse QBV, making the latency universal to TSN features.

Discussed with i226 HW owner (Shalev, Avi) and we were in agreement that
the term "launch time" used in Section 7.5.2.6 is not clear and can be
easily misinterpreted. Avi will update this section to:
"When TQAVCTRL.TRANSMIT_MODE = TSN, the latency between transmission
scheduling and the time the packet is transmitted to the network is listed
in Table 7-61."

Fix this issue by using igc_tsn_is_tx_mode_in_tsn() as a condition to
write to gtxoffset, aligning with the newly updated SW User Manual.

Tested:
1. Enrol taprio on talker board
   base-time 0
   cycle-time 1000000
   flags 0x2
   index 0 cmd S gatemask 0x1 interval1
   index 0 cmd S gatemask 0x1 interval2

   Note:
   interval1 = interval for a 64 bytes packet to go through
   interval2 = cycle-time - interval1

2. Take tcpdump on listener board

3. Use udp tai app on talker to send packets to listener

4. Check the timestamp on listener via wireshark

Test Result:
100 Mbps: 113 ~193 ns
1000 Mbps: 52 ~ 84 ns
2500 Mbps: 95 ~ 223 ns

Note that the test result is similar to the patch "igc: Correct the
launchtime offset".

Fixes: 790835fcc0cb ("igc: Correct the launchtime offset")
Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>
---
 drivers/net/ethernet/intel/igc/igc_tsn.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
index 26dbe3442ad1..e95502fc844b 100644
--- a/drivers/net/ethernet/intel/igc/igc_tsn.c
+++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
@@ -61,7 +61,7 @@ void igc_tsn_adjust_txtime_offset(struct igc_adapter *adapter)
 	struct igc_hw *hw = &adapter->hw;
 	u16 txoffset;
 
-	if (!is_any_launchtime(adapter))
+	if (!igc_tsn_is_tx_mode_in_tsn(adapter))
 		return;
 
 	switch (adapter->link_speed) {
-- 
2.25.1

Re: [PATCH iwl-net v1 2/4] igc: Fix reset adapter logics when tx mode change

[Simon Horman]

On Tue, Jul 02, 2024 at 12:09:24AM -0400, Faizal Rahim wrote:
> Following the "igc: Fix TX Hang issue when QBV Gate is close" changes,
> remaining issues with the reset adapter logic in igc_tsn_offload_apply()
> have been observed:
> 
> 1. The reset adapter logics for i225 and i226 differ, although they should
>    be the same according to the guidelines in I225/6 HW Design Section
>    7.5.2.1 on software initialization during tx mode changes.
> 2. The i225 resets adapter every time, even though tx mode doesn't change.
>    This occurs solely based on the condition  igc_is_device_id_i225() when
>    calling schedule_work().
> 3. i226 doesn't reset adapter for tsn->legacy tx mode changes. It only
>    resets adapter for legacy->tsn tx mode transitions.
> 4. qbv_count introduced in the patch is actually not needed; in this
>    context, a non-zero value of qbv_count is used to indicate if tx mode
>    was unconditionally set to tsn in igc_tsn_enable_offload(). This could
>    be replaced by checking the existing register
>    IGC_TQAVCTRL_TRANSMIT_MODE_TSN bit.
> 
> This patch resolves all issues and enters schedule_work() to reset the
> adapter only when changing tx mode. It also removes reliance on qbv_count.
> 
> qbv_count field will be removed in a future patch.
> 
> Test ran:
> 
> 1. Verify reset adapter behaviour in i225/6:
>    a) Enrol a new GCL
>       Reset adapter observed (tx mode change legacy->tsn)
>    b) Enrol a new GCL without deleting qdisc
>       No reset adapter observed (tx mode remain tsn->tsn)
>    c) Delete qdisc
>       Reset adapter observed (tx mode change tsn->legacy)
> 
> 2. Tested scenario from "igc: Fix TX Hang issue when QBV Gate is closed"
>    to confirm it remains resolved.
> 
> Fixes: 175c241288c0 ("igc: Fix TX Hang issue when QBV Gate is closed")
> Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>

Hi Faizal,

Nits below not withstahdning, this looks good to me.

Reviewed-by: Simon Horman <horms@kernel.org>

> ---
>  drivers/net/ethernet/intel/igc/igc_tsn.c | 26 +++++++++++++++++++++---
>  1 file changed, 23 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
> index 02dd41aff634..61f047ebf34d 100644
> --- a/drivers/net/ethernet/intel/igc/igc_tsn.c
> +++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
> @@ -49,6 +49,13 @@ static unsigned int igc_tsn_new_flags(struct igc_adapter *adapter)
>  	return new_flags;
>  }
>  
> +static bool igc_tsn_is_tx_mode_in_tsn(struct igc_adapter *adapter)
> +{
> +	struct igc_hw *hw = &adapter->hw;
> +
> +	return (bool)(rd32(IGC_TQAVCTRL) & IGC_TQAVCTRL_TRANSMIT_MODE_TSN);

Perhaps it is more a question of taste than anything else.
But my preference, FIIW, is to avoid casts.
And I think in this case using !! is a common pattern.

(Completely untested!)

	return !!(rd32(IGC_TQAVCTRL) & IGC_TQAVCTRL_TRANSMIT_MODE_TSN);

> +}
> +
>  void igc_tsn_adjust_txtime_offset(struct igc_adapter *adapter)
>  {
>  	struct igc_hw *hw = &adapter->hw;
> @@ -334,15 +341,28 @@ int igc_tsn_reset(struct igc_adapter *adapter)
>  	return err;
>  }
>  
> +static bool igc_tsn_will_tx_mode_change(struct igc_adapter *adapter)
> +{
> +	bool any_tsn_enabled = (bool)(igc_tsn_new_flags(adapter) &
> +			       IGC_FLAG_TSN_ANY_ENABLED);

Ditto.

> +
> +	if ((any_tsn_enabled && !igc_tsn_is_tx_mode_in_tsn(adapter)) ||
> +	    (!any_tsn_enabled && igc_tsn_is_tx_mode_in_tsn(adapter)))
> +		return true;
> +	else
> +		return false;

Likewise, this is probably more a matter of taste than anything else.
But I think this could be expressed as:

(Completely untested!)

	return (any_tsn_enabled && !igc_tsn_is_tx_mode_in_tsn(adapter)) ||
		(!any_tsn_enabled && igc_tsn_is_tx_mode_in_tsn(adapter));

Similarly in the previous patch of this series.

> +}
> +
>  int igc_tsn_offload_apply(struct igc_adapter *adapter)
>  {
>  	struct igc_hw *hw = &adapter->hw;
>  
> -	/* Per I225/6 HW Design Section 7.5.2.1, transmit mode
> -	 * cannot be changed dynamically. Require reset the adapter.
> +	/* Per I225/6 HW Design Section 7.5.2.1 guideline, if tx mode change
> +	 * from legacy->tsn or tsn->legacy, then reset adapter is needed.
>  	 */
>  	if (netif_running(adapter->netdev) &&
> -	    (igc_is_device_id_i225(hw) || !adapter->qbv_count)) {
> +	    (igc_is_device_id_i225(hw) || igc_is_device_id_i226(hw)) &&
> +	     igc_tsn_will_tx_mode_change(adapter)) {
>  		schedule_work(&adapter->reset_task);
>  		return 0;
>  	}
> -- 
> 2.25.1
> 
> 

Re: [PATCH iwl-net v1 1/4] igc: Fix qbv_config_change_errors logics

[Simon Horman]

On Tue, Jul 02, 2024 at 12:09:23AM -0400, Faizal Rahim wrote:
> When user issues these cmds:
> 1. Either a) or b)
>    a) mqprio with hardware offload disabled
>    b) taprio with txtime-assist feature enabled
> 2. etf
> 3. tc qdisc delete
> 4. taprio with base time in the past
> 
> At step 4, qbv_config_change_errors wrongly increased by 1.
> 
> Excerpt from IEEE 802.1Q-2018 8.6.9.3.1:
> "If AdminBaseTime specifies a time in the past, and the current schedule
> is running, then: Increment ConfigChangeError counter"
> 
> qbv_config_change_errors should only increase if base time is in the past
> and no taprio is active. In user perspective, taprio was not active when
> first triggered at step 4. However, i225/6 reuses qbv for etf, so qbv is
> enabled with a dummy schedule at step 2 where it enters
> igc_tsn_enable_offload() and qbv_count got incremented to 1. At step 4, it
> enters igc_tsn_enable_offload() again, qbv_count is incremented to 2.
> Because taprio is running, tc_setup_type is TC_SETUP_QDISC_ETF and
> qbv_count > 1, qbv_config_change_errors value got incremented.
> 
> This issue happens due to reliance on qbv_count field where a non-zero
> value indicates that taprio is running. But qbv_count increases
> regardless if taprio is triggered by user or by other tsn feature. It does
> not align with qbv_config_change_errors expectation where it is only
> concerned with taprio triggered by user.
> 
> Fixing this by relocating the qbv_config_change_errors logic to
> igc_save_qbv_schedule(), eliminating reliance on qbv_count and its
> inaccuracies from i225/6's multiple uses of qbv feature for other TSN
> features.
> 
> The new function created: igc_tsn_is_taprio_activated_by_user() uses
> taprio_offload_enable field to indicate that the current running taprio
> was triggered by user, instead of triggered by non-qbv feature like etf.
> 
> Fixes: ae4fe4698300 ("igc: Add qbv_config_change_errors counter")
> Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>

Thanks Faizal,

My nit below notwithstanding, this looks good to me.

Reviewed-by: Simon Horman <horms@kernel.org>

...

> diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
> index 22cefb1eeedf..02dd41aff634 100644
> --- a/drivers/net/ethernet/intel/igc/igc_tsn.c
> +++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
> @@ -78,6 +78,17 @@ void igc_tsn_adjust_txtime_offset(struct igc_adapter *adapter)
>  	wr32(IGC_GTXOFFSET, txoffset);
>  }
>  
> +bool igc_tsn_is_taprio_activated_by_user(struct igc_adapter *adapter)
> +{
> +	struct igc_hw *hw = &adapter->hw;
> +
> +	if ((rd32(IGC_BASET_H) || rd32(IGC_BASET_L)) &&
> +	    adapter->taprio_offload_enable)
> +		return true;
> +	else
> +		return false;

As per my response to patch 2/4, I think something like this is a bit
nicer:

(Completely untested!)

	return (rd32(IGC_BASET_H) || rd32(IGC_BASET_L)) &&
		adapter->taprio_offload_enable;


> +}
> +
>  /* Returns the TSN specific registers to their default values after
>   * the adapter is reset.
>   */

...

Re: [PATCH iwl-net v1 3/4] igc: Remove unused qbv_count

[Simon Horman]

On Tue, Jul 02, 2024 at 12:09:25AM -0400, Faizal Rahim wrote:
> Removing qbv_count which is now obsolete after these 2 patches:
> "igc: Fix reset adapter logics when tx mode change"
> "igc: Fix qbv_config_change_errors logics"
> 
> The variable qbv_count serves to indicate whether Taprio is active or if
> the tx mode is in TSN (IGC_TQAVCTRL_TRANSMIT_MODE_TSN). This is due to its
> unconditional increment within igc_tsn_enable_offload(), which both runs
> Taprio and sets the tx mode to TSN.
> 
> Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>

Hi Faizal,

This change looks good to me.
However, it seems more appropriate as a clean-up for iwl-next
once the previous to patches make it there via iwl-net.

That notwithstanding,

Reviewed-by: Simon Horman <horms@kernel.org>

...

Re: [PATCH iwl-net v1 4/4] igc: Fix qbv tx latency by setting gtxoffset

[Simon Horman]

On Tue, Jul 02, 2024 at 12:09:26AM -0400, Faizal Rahim wrote:
> A large tx latency issue was discovered during testing when only QBV was
> enabled. The issue occurs because gtxoffset was not set when QBV is
> active, it was only set when launch time is active.
> 
> The patch "igc: Correct the launchtime offset" only sets gtxoffset when
> the launchtime_enable field is set by the user. Enabling launchtime_enable
> ultimately sets the register IGC_TXQCTL_QUEUE_MODE_LAUNCHT (referred to as
> LaunchT in the SW user manual).
> 
> Section 7.5.2.6 of the IGC i225/6 SW User Manual Rev 1.2.4 states:
> "The latency between transmission scheduling (launch time) and the
> time the packet is transmitted to the network is listed in Table 7-61."
> 
> However, the patch misinterprets the phrase "launch time" in that section
> by assuming it specifically refers to the LaunchT register, whereas it
> actually denotes the generic term for when a packet is released from the
> internal buffer to the MAC transmit logic.
> 
> This launch time, as per that section, also implicitly refers to the QBV
> gate open time, where a packet waits in the buffer for the QBV gate to
> open. Therefore, latency applies whenever QBV is in use. TSN features such
> as QBU and QAV reuse QBV, making the latency universal to TSN features.
> 
> Discussed with i226 HW owner (Shalev, Avi) and we were in agreement that
> the term "launch time" used in Section 7.5.2.6 is not clear and can be
> easily misinterpreted. Avi will update this section to:
> "When TQAVCTRL.TRANSMIT_MODE = TSN, the latency between transmission
> scheduling and the time the packet is transmitted to the network is listed
> in Table 7-61."
> 
> Fix this issue by using igc_tsn_is_tx_mode_in_tsn() as a condition to
> write to gtxoffset, aligning with the newly updated SW User Manual.
> 
> Tested:
> 1. Enrol taprio on talker board
>    base-time 0
>    cycle-time 1000000
>    flags 0x2
>    index 0 cmd S gatemask 0x1 interval1
>    index 0 cmd S gatemask 0x1 interval2
> 
>    Note:
>    interval1 = interval for a 64 bytes packet to go through
>    interval2 = cycle-time - interval1
> 
> 2. Take tcpdump on listener board
> 
> 3. Use udp tai app on talker to send packets to listener
> 
> 4. Check the timestamp on listener via wireshark
> 
> Test Result:
> 100 Mbps: 113 ~193 ns
> 1000 Mbps: 52 ~ 84 ns
> 2500 Mbps: 95 ~ 223 ns
> 
> Note that the test result is similar to the patch "igc: Correct the
> launchtime offset".
> 
> Fixes: 790835fcc0cb ("igc: Correct the launchtime offset")
> Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>

Reviewed-by: Simon Horman <horms@kernel.org>

Re: [PATCH iwl-net v1 3/4] igc: Remove unused qbv_count

[Abdul Rahim, Faizal]

On 3/7/2024 11:10 pm, Simon Horman wrote:
> On Tue, Jul 02, 2024 at 12:09:25AM -0400, Faizal Rahim wrote:
>> Removing qbv_count which is now obsolete after these 2 patches:
>> "igc: Fix reset adapter logics when tx mode change"
>> "igc: Fix qbv_config_change_errors logics"
>>
>> The variable qbv_count serves to indicate whether Taprio is active or if
>> the tx mode is in TSN (IGC_TQAVCTRL_TRANSMIT_MODE_TSN). This is due to its
>> unconditional increment within igc_tsn_enable_offload(), which both runs
>> Taprio and sets the tx mode to TSN.
>>
>> Signed-off-by: Faizal Rahim <faizal.abdul.rahim@linux.intel.com>
> 
> Hi Faizal,
> 
> This change looks good to me.
> However, it seems more appropriate as a clean-up for iwl-next
> once the previous to patches make it there via iwl-net.
> 
> That notwithstanding,
> 
> Reviewed-by: Simon Horman <horms@kernel.org>
> 
> ...

Got it, will do that.
Thanks.

Re: [PATCH iwl-net v1 2/4] igc: Fix reset adapter logics when tx mode change

[Abdul Rahim, Faizal]

>> ---
>>   drivers/net/ethernet/intel/igc/igc_tsn.c | 26 +++++++++++++++++++++---
>>   1 file changed, 23 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
>> index 02dd41aff634..61f047ebf34d 100644
>> --- a/drivers/net/ethernet/intel/igc/igc_tsn.c
>> +++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
>> @@ -49,6 +49,13 @@ static unsigned int igc_tsn_new_flags(struct igc_adapter *adapter)
>>   	return new_flags;
>>   }
>>   
>> +static bool igc_tsn_is_tx_mode_in_tsn(struct igc_adapter *adapter)
>> +{
>> +	struct igc_hw *hw = &adapter->hw;
>> +
>> +	return (bool)(rd32(IGC_TQAVCTRL) & IGC_TQAVCTRL_TRANSMIT_MODE_TSN);
> 
> Perhaps it is more a question of taste than anything else.
> But my preference, FIIW, is to avoid casts.
> And I think in this case using !! is a common pattern.
> 
> (Completely untested!)
> 
> 	return !!(rd32(IGC_TQAVCTRL) & IGC_TQAVCTRL_TRANSMIT_MODE_TSN);
> 

Sure, will update.

>> +
>> +	if ((any_tsn_enabled && !igc_tsn_is_tx_mode_in_tsn(adapter)) ||
>> +	    (!any_tsn_enabled && igc_tsn_is_tx_mode_in_tsn(adapter)))
>> +		return true;
>> +	else
>> +		return false;
> 
> Likewise, this is probably more a matter of taste than anything else.
> But I think this could be expressed as:
> 
> (Completely untested!)
> 
> 	return (any_tsn_enabled && !igc_tsn_is_tx_mode_in_tsn(adapter)) ||
> 		(!any_tsn_enabled && igc_tsn_is_tx_mode_in_tsn(adapter));
> 
> Similarly in the previous patch of this series.
> 

Will update, your suggestion is better, lesser parenthesis.
Thanks.

Re: [PATCH iwl-net v1 1/4] igc: Fix qbv_config_change_errors logics

[Abdul Rahim, Faizal]

>> diff --git a/drivers/net/ethernet/intel/igc/igc_tsn.c b/drivers/net/ethernet/intel/igc/igc_tsn.c
>> index 22cefb1eeedf..02dd41aff634 100644
>> --- a/drivers/net/ethernet/intel/igc/igc_tsn.c
>> +++ b/drivers/net/ethernet/intel/igc/igc_tsn.c
>> @@ -78,6 +78,17 @@ void igc_tsn_adjust_txtime_offset(struct igc_adapter *adapter)
>>   	wr32(IGC_GTXOFFSET, txoffset);
>>   }
>>   
>> +bool igc_tsn_is_taprio_activated_by_user(struct igc_adapter *adapter)
>> +{
>> +	struct igc_hw *hw = &adapter->hw;
>> +
>> +	if ((rd32(IGC_BASET_H) || rd32(IGC_BASET_L)) &&
>> +	    adapter->taprio_offload_enable)
>> +		return true;
>> +	else
>> +		return false;
> 
> As per my response to patch 2/4, I think something like this is a bit
> nicer:
> 
> (Completely untested!)
> 
> 	return (rd32(IGC_BASET_H) || rd32(IGC_BASET_L)) &&
> 		adapter->taprio_offload_enable;
> 
> 

Will update, thanks.