RE: [patch net] net: fec: cache statistics while device is down

[Andy Duan]

From: Nikita Yushchenko <nikita.yoush@xxxxxxxxxxxxxxxxxx> Sent: Monday, November 28, 2016 10:27 PM
 >To: David S. Miller <davem@xxxxxxxxxxxxx>; Andy Duan
 ><fugang.duan@xxxxxxx>; Troy Kisky <troy.kisky@xxxxxxxxxxxxxxxxxxx>;
 >Andrew Lunn <andrew@xxxxxxx>; Eric Nelson <eric@xxxxxxxxxx>; Philippe
 >Reynes <tremyfr@xxxxxxxxx>; Johannes Berg <johannes@xxxxxxxxxxxxxxxx>;
 >netdev@xxxxxxxxxxxxxxx
 >Cc: Chris Healy <cphealy@xxxxxxxxx>; Fabio Estevam
 ><fabio.estevam@xxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; Nikita
 >Yushchenko <nikita.yoush@xxxxxxxxxxxxxxxxxx>
 >Subject: [patch net] net: fec: cache statistics while device is down
 >
 >Execution 'ethtool -S' on fec device that is down causes OOPS on Vybrid
 >board:
 >
 >Unhandled fault: external abort on non-linefetch (0x1008) at 0xe0898200 pgd
 >= ddecc000 [e0898200] *pgd=9e406811, *pte=400d1653, *ppte=400d1453
 >Internal error: : 1008 [#1] SMP ARM ...
 >
 >Reason of OOPS is that fec_enet_get_ethtool_stats() accesses fec registers
 >while IPG clock is stopped by PM.
 >
 >Fix that by caching statistics in fec_enet_private. Cache is updated just
 >before statistics request if device is up, and also just before turning device
 >off on down path.
 >
 >Additional locking is not needed, since cached statistics is always updated
 >under rtnl_lock().
 >
 >Signed-off-by: Nikita Yushchenko <nikita.yoush@xxxxxxxxxxxxxxxxxx>
 >---
 > drivers/net/ethernet/freescale/fec.h      |  2 ++
 > drivers/net/ethernet/freescale/fec_main.c | 21 +++++++++++++++++----
 > 2 files changed, 19 insertions(+), 4 deletions(-)
 >
 >diff --git a/drivers/net/ethernet/freescale/fec.h
 >b/drivers/net/ethernet/freescale/fec.h
 >index c865135f3cb9..5ea740b4cf14 100644
 >--- a/drivers/net/ethernet/freescale/fec.h
 >+++ b/drivers/net/ethernet/freescale/fec.h
 >@@ -574,6 +574,8 @@ struct fec_enet_private {
 > 	unsigned int reload_period;
 > 	int pps_enable;
 > 	unsigned int next_counter;
 >+
 >+	u64 ethtool_stats[0];
 > };
 >
 > void fec_ptp_init(struct platform_device *pdev); diff --git
 >a/drivers/net/ethernet/freescale/fec_main.c
 >b/drivers/net/ethernet/freescale/fec_main.c
 >index 5aa9d4ded214..7da2d94ec8e5 100644
 >--- a/drivers/net/ethernet/freescale/fec_main.c
 >+++ b/drivers/net/ethernet/freescale/fec_main.c
 >@@ -2313,14 +2313,24 @@ static const struct fec_stat {
 > 	{ "IEEE_rx_octets_ok", IEEE_R_OCTETS_OK },  };
 >
 >-static void fec_enet_get_ethtool_stats(struct net_device *dev,
 >-	struct ethtool_stats *stats, u64 *data)
 >+static void fec_enet_update_ethtool_stats(struct net_device *dev)
 > {
 > 	struct fec_enet_private *fep = netdev_priv(dev);
 > 	int i;
 >
 > 	for (i = 0; i < ARRAY_SIZE(fec_stats); i++)
 >-		data[i] = readl(fep->hwp + fec_stats[i].offset);
 >+		fep->ethtool_stats[i] = readl(fep->hwp +
 >fec_stats[i].offset); }
 >+
 >+static void fec_enet_get_ethtool_stats(struct net_device *dev,
 >+				       struct ethtool_stats *stats, u64 *data) {
 >+	struct fec_enet_private *fep = netdev_priv(dev);
 >+
 >+	if (netif_running(dev))
 >+		fec_enet_update_ethtool_stats(dev);
 >+
 >+	memcpy(data, fep->ethtool_stats, ARRAY_SIZE(fec_stats) *
 >sizeof(u64));
 > }
 >
 > static void fec_enet_get_strings(struct net_device *netdev, @@ -2874,6
 >+2884,8 @@ fec_enet_close(struct net_device *ndev)
 > 	if (fep->quirks & FEC_QUIRK_ERR006687)
 > 		imx6q_cpuidle_fec_irqs_unused();
 >
 >+	fec_enet_update_ethtool_stats(ndev);
 >+
If user never open the interface, ethtool_stats[] always is 0 that are not expected.
So, it also should be called at . fec_enet_init() ?

 > 	fec_enet_clk_enable(ndev, false);
 > 	pinctrl_pm_select_sleep_state(&fep->pdev->dev);
 > 	pm_runtime_mark_last_busy(&fep->pdev->dev);
 >@@ -3278,7 +3290,8 @@ fec_probe(struct platform_device *pdev)
 > 	fec_enet_get_queue_num(pdev, &num_tx_qs, &num_rx_qs);
 >
 > 	/* Init network device */
 >-	ndev = alloc_etherdev_mqs(sizeof(struct fec_enet_private),
 >+	ndev = alloc_etherdev_mqs(sizeof(struct fec_enet_private) +
 >+				  ARRAY_SIZE(fec_stats) * sizeof(u64),
 > 				  num_tx_qs, num_rx_qs);
 > 	if (!ndev)
 > 		return -ENOMEM;
 >--
 >2.1.4