[PATCH net-next v7 09/14] net: lan966x: add shutdown callback to stop the FDMA on reboot

[Daniel Machon <daniel.machon@microchip.com>]

As a PCIe endpoint, lan966x is not reset by a host reboot: its FDMA
channels and interrupt sources stay armed, and the OIC ORs every
source into the shared PCIe INTx, asserted before the driver has
re-probed. A still-active channel also keeps write access to host
memory the next kernel will reuse.

Add a shutdown callback that:
- frees the ana, xtr and FDMA irqs, masking and unmapping them at
  the OIC (disable_irq() would leave both set - the OIC has no
  irq_disable())
- masks the analyzer source, armed unconditionally by lan966x_init()
  and re-armed by the MAC table's age timer
- stops and detaches the netdevs, draining in-flight xmit and
  clearing netif_device_present() so ndo_open/ndo_change_mtu cannot
  re-enter the FDMA against a disabled NAPI
- disables both FDMA channels and masks their interrupts
- unmaps the outbound ATU windows, leaving none armed

NAPI is skipped when fdma_ndev is unset (a probed switch with no
usable port never adds one), and XDP attach cannot re-enter either,
since lan966x_xdp_setup() returns early on PCIe before touching the
FDMA.

Only the PCIe instantiation needs this - the SoC one resets with the
chip - so the callback returns early on a platform device; the check
is at runtime since .shutdown belongs to the driver, and a
PCIe-enabled kernel binds both.

FDMA_INTR_ENA persists across a warm reboot, so also restore the
full enable in lan966x_fdma_rx_start(), run after both rings are
allocated, re-arming both backends from one site.

Tested-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: Daniel Machon <daniel.machon@microchip.com>
---
 .../net/ethernet/microchip/lan966x/lan966x_fdma.c  |  4 ++
 .../net/ethernet/microchip/lan966x/lan966x_main.c  | 56 ++++++++++++++++++++++
 .../net/ethernet/microchip/lan966x/lan966x_regs.h  | 15 ++++++
 3 files changed, 75 insertions(+)

diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
index 2695bc41e52a..6fb2482eeb17 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
@@ -146,6 +146,10 @@ void lan966x_fdma_rx_start(struct lan966x_rx *rx)
 	struct fdma *fdma = &rx->fdma;
 	u32 mask;
 
+	lan_wr(FDMA_INTR_ENA_INTR_PORT_ENA_SET(GENMASK(1, 0)) |
+	       FDMA_INTR_ENA_INTR_CH_ENA_SET(GENMASK(7, 0)),
+	       lan966x, FDMA_INTR_ENA);
+
 	lan_wr(FDMA_CH_CFG_CH_DCB_DB_CNT_SET(fdma->n_dbs) |
 	       FDMA_CH_CFG_CH_INTR_DB_EOF_ONLY_SET(1) |
 	       FDMA_CH_CFG_CH_INJ_PORT_SET(0) |
diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
index 11094a381ec2..2c1e2bc12024 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
@@ -1324,9 +1324,65 @@ static void lan966x_remove(struct platform_device *pdev)
 	debugfs_remove_recursive(lan966x->debugfs_root);
 }
 
+static void lan966x_shutdown(struct platform_device *pdev)
+{
+	struct lan966x *lan966x = platform_get_drvdata(pdev);
+
+	/* As a PCIe endpoint the switch is not reset by the host reboot, so it
+	 * has to be quiesced here:
+	 *
+	 *   Free the irqs and mask the sources: no source can assert INTx.
+	 *   Disable NAPI: the teardown must not race a poll.
+	 *   Stop and detach the netdevs: drains xmit, closes ndo_open and MTU.
+	 *   Stop the FDMA channels: waits for the engine to go idle.
+	 *   Unmap the ATU windows: revokes the engine's access to host memory.
+	 */
+	if (!lan966x_is_pci(lan966x))
+		return;
+
+	if (lan966x->xtr_irq > 0)
+		devm_free_irq(lan966x->dev, lan966x->xtr_irq, lan966x);
+	if (lan966x->ana_irq > 0)
+		devm_free_irq(lan966x->dev, lan966x->ana_irq, lan966x);
+	if (lan966x->fdma_irq > 0)
+		devm_free_irq(lan966x->dev, lan966x->fdma_irq, lan966x);
+
+	lan_wr(0, lan966x, ANA_ANAINTR);
+
+	if (!lan966x->fdma)
+		return;
+
+	rtnl_lock();
+
+	if (lan966x->fdma_ndev)
+		napi_disable(&lan966x->napi);
+
+	for (int p = 0; p < lan966x->num_phys_ports; p++) {
+		if (!lan966x->ports[p] || !lan966x->ports[p]->dev)
+			continue;
+
+		netif_tx_disable(lan966x->ports[p]->dev);
+		netif_device_detach(lan966x->ports[p]->dev);
+	}
+
+	lan966x_fdma_rx_disable(&lan966x->rx);
+	lan966x_fdma_tx_disable(&lan966x->tx);
+
+	lan_wr(0, lan966x, FDMA_INTR_ENA);
+	lan_wr(0, lan966x, FDMA_INTR_DB_ENA);
+
+#if IS_ENABLED(CONFIG_MCHP_LAN966X_PCI)
+	fdma_pci_atu_region_unmap(lan966x->rx.fdma.atu_region);
+	fdma_pci_atu_region_unmap(lan966x->tx.fdma.atu_region);
+#endif
+
+	rtnl_unlock();
+}
+
 static struct platform_driver lan966x_driver = {
 	.probe = lan966x_probe,
 	.remove = lan966x_remove,
+	.shutdown = lan966x_shutdown,
 	.driver = {
 		.name = "lan966x-switch",
 		.of_match_table = lan966x_match,
diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_regs.h b/drivers/net/ethernet/microchip/lan966x/lan966x_regs.h
index 4b553927d2e0..aba0d36ae6b5 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_regs.h
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_regs.h
@@ -1039,6 +1039,21 @@ enum lan966x_target {
 /*      FDMA:FDMA:FDMA_INTR_ERR */
 #define FDMA_INTR_ERR             __REG(TARGET_FDMA, 0, 1, 8, 0, 1, 428, 400, 0, 1, 4)
 
+/*      FDMA:FDMA:FDMA_INTR_ENA */
+#define FDMA_INTR_ENA             __REG(TARGET_FDMA, 0, 1, 8, 0, 1, 428, 404, 0, 1, 4)
+
+#define FDMA_INTR_ENA_INTR_PORT_ENA              GENMASK(9, 8)
+#define FDMA_INTR_ENA_INTR_PORT_ENA_SET(x)\
+	FIELD_PREP(FDMA_INTR_ENA_INTR_PORT_ENA, x)
+#define FDMA_INTR_ENA_INTR_PORT_ENA_GET(x)\
+	FIELD_GET(FDMA_INTR_ENA_INTR_PORT_ENA, x)
+
+#define FDMA_INTR_ENA_INTR_CH_ENA                GENMASK(7, 0)
+#define FDMA_INTR_ENA_INTR_CH_ENA_SET(x)\
+	FIELD_PREP(FDMA_INTR_ENA_INTR_CH_ENA, x)
+#define FDMA_INTR_ENA_INTR_CH_ENA_GET(x)\
+	FIELD_GET(FDMA_INTR_ENA_INTR_CH_ENA, x)
+
 /*      FDMA:FDMA:FDMA_ERRORS */
 #define FDMA_ERRORS               __REG(TARGET_FDMA, 0, 1, 8, 0, 1, 428, 412, 0, 1, 4)
 

-- 
2.34.1