[PATCH net v3 2/6] net: stmmac: selftests: Validate EEE based on the actual LPI timer value

[Maxime Chevallier]

The EEE selftest is a 2-step test :
 - It validates that we enter in LPI mode with the
   irq_tx_path_in_lpi_mode_n counter
 - It then validates that we exit LPI when sending a frame, with the
   irq_tx_path_exit_lpi_mode_n counter.

The current state of the test lacks 2 main things :

 - We don't know exactly when was the previous frame sent (it's from the
   previous selftest)

 - The timeout is hardcoded, while the LPI is entered after a
   user-configurable delay. On top of that, the timeout loop uses a
   pre-decrement iterator (--retries) that actually only iterate nine
   times, so 900ms while the default LPI value is 1 second.

Let's therefore make it more deterministic :

 - Send a frame at the beginning of the test
 - Wait for more than the lpi timer value, we timeout after about twice
   the value,
 - Then send another frame, and verify that we do go out of LPI, also
   with a timeout.

As LPI timer can get pretty high, bail out if LPI timer is over 5
seconds.

Note that the test's goal isn't to validate the LPI timer value itself,
only that we enter/leave LPI mode.

Fixes: 091810dbded9 ("net: stmmac: Introduce selftests support")
Reviewed-by: Nicolai Buchwitz <nb@xxxxxxxxxxx>
Signed-off-by: Maxime Chevallier <maxime.chevallier@xxxxxxxxxxx>
---
 .../stmicro/stmmac/stmmac_selftests.c         | 44 ++++++++++++++++---
 1 file changed, 37 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
index 6503678b646e..df28741abf2b 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c
@@ -30,6 +30,7 @@ struct stmmachdr {
 			      sizeof(struct stmmachdr))
 #define STMMAC_TEST_PKT_MAGIC	0xdeadcafecafedeadULL
 #define STMMAC_LB_TIMEOUT	msecs_to_jiffies(200)
+#define STMMAC_SFT_MAX_LPI	(5 * USEC_PER_SEC)
 
 struct stmmac_packet_attrs {
 	int vlan;
@@ -462,12 +463,16 @@ static int stmmac_test_mmc(struct stmmac_priv *priv)
 static int stmmac_test_eee(struct stmmac_priv *priv)
 {
 	struct stmmac_extra_stats *initial, *final;
-	int retries = 10;
+	unsigned long timeout, max_duration;
 	int ret;
 
 	if (!priv->dma_cap.eee || !priv->eee_active)
 		return -EOPNOTSUPP;
 
+	/* Bail out if the configured LPI timer is too long */
+	if (priv->tx_lpi_timer > STMMAC_SFT_MAX_LPI)
+		return -EOPNOTSUPP;
+
 	initial = kzalloc_obj(*initial);
 	if (!initial)
 		return -ENOMEM;
@@ -478,14 +483,21 @@ static int stmmac_test_eee(struct stmmac_priv *priv)
 		goto out_free_initial;
 	}
 
+	/* Snapshot stats, we want to count the in_lpi events. We may enter
+	 * LPI just after the packet was sent.
+	 */
 	memcpy(initial, &priv->xstats, sizeof(*initial));
 
+	/* Send a frame, then wait to enter LPI */
 	ret = stmmac_test_mac_loopback(priv);
 	if (ret)
 		goto out_free_final;
 
+	max_duration = usecs_to_jiffies(2 * priv->tx_lpi_timer);
+
 	/* We have no traffic in the line so, sooner or later it will go LPI */
-	while (--retries) {
+	timeout = jiffies + max_duration;
+	while (!time_after(jiffies, timeout)) {
 		memcpy(final, &priv->xstats, sizeof(*final));
 
 		if (final->irq_tx_path_in_lpi_mode_n >
@@ -494,20 +506,38 @@ static int stmmac_test_eee(struct stmmac_priv *priv)
 		msleep(100);
 	}
 
-	if (!retries) {
+	memcpy(final, &priv->xstats, sizeof(*final));
+	if (final->irq_tx_path_in_lpi_mode_n <=
+	    initial->irq_tx_path_in_lpi_mode_n) {
 		ret = -ETIMEDOUT;
 		goto out_free_final;
 	}
 
-	if (final->irq_tx_path_in_lpi_mode_n <=
-	    initial->irq_tx_path_in_lpi_mode_n) {
-		ret = -EINVAL;
+	/* Re-snapshot, as we want to measure exit_lpi events. We should be
+	 * in LPI right now.
+	 */
+	memcpy(initial, &priv->xstats, sizeof(*initial));
+
+	/* TX something so we go out of LPI */
+	ret = stmmac_test_mac_loopback(priv);
+	if (ret)
 		goto out_free_final;
+
+	/* Wait for the exit LPI interrupt */
+	timeout = jiffies + max_duration;
+	while (!time_after(jiffies, timeout)) {
+		memcpy(final, &priv->xstats, sizeof(*final));
+
+		if (final->irq_tx_path_exit_lpi_mode_n >
+		    initial->irq_tx_path_exit_lpi_mode_n)
+			break;
+		msleep(100);
 	}
 
+	memcpy(final, &priv->xstats, sizeof(*final));
 	if (final->irq_tx_path_exit_lpi_mode_n <=
 	    initial->irq_tx_path_exit_lpi_mode_n) {
-		ret = -EINVAL;
+		ret = -ETIMEDOUT;
 		goto out_free_final;
 	}
 
-- 
2.55.0