[PATCH net] net: atlantic: fix warning during hot unplug

[Jacob Moroni <mail@jakemoroni.com>]

Firmware deinitialization performs MMIO accesses which are not
necessary if the device has already been removed. In some cases,
these accesses happen via readx_poll_timeout_atomic which ends up
timing out, resulting in a warning at hw_atl2_utils_fw.c:112:

[  104.595913] Call Trace:
[  104.595915]  <TASK>
[  104.595918]  ? show_regs+0x6c/0x80
[  104.595923]  ? __warn+0x8d/0x150
[  104.595925]  ? aq_a2_fw_deinit+0xcf/0xe0 [atlantic]
[  104.595934]  ? report_bug+0x182/0x1b0
[  104.595938]  ? handle_bug+0x6e/0xb0
[  104.595940]  ? exc_invalid_op+0x18/0x80
[  104.595942]  ? asm_exc_invalid_op+0x1b/0x20
[  104.595944]  ? aq_a2_fw_deinit+0xcf/0xe0 [atlantic]
[  104.595952]  ? aq_a2_fw_deinit+0xcf/0xe0 [atlantic]
[  104.595959]  aq_nic_deinit.part.0+0xbd/0xf0 [atlantic]
[  104.595964]  aq_nic_deinit+0x17/0x30 [atlantic]
[  104.595970]  aq_ndev_close+0x2b/0x40 [atlantic]
[  104.595975]  __dev_close_many+0xad/0x160
[  104.595978]  dev_close_many+0x99/0x170
[  104.595979]  unregister_netdevice_many_notify+0x18b/0xb20
[  104.595981]  ? __call_rcu_common+0xcd/0x700
[  104.595984]  unregister_netdevice_queue+0xc6/0x110
[  104.595986]  unregister_netdev+0x1c/0x30
[  104.595988]  aq_pci_remove+0xb1/0xc0 [atlantic]

Fix this by skipping firmware deinitialization altogether if the
PCI device is no longer present.

Tested with an AQC113 attached via Thunderbolt by performing
repeated unplug cycles while traffic was running via iperf.

Signed-off-by: Jacob Moroni <mail@jakemoroni.com>
---
 drivers/net/ethernet/aquantia/atlantic/aq_nic.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/aquantia/atlantic/aq_nic.c b/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
index fe0e3e2a8117..e2ae95a01947 100644
--- a/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
+++ b/drivers/net/ethernet/aquantia/atlantic/aq_nic.c
@@ -1428,7 +1428,7 @@ void aq_nic_deinit(struct aq_nic_s *self, bool link_down)
 	unsigned int i = 0U;
 
 	if (!self)
-		goto err_exit;
+		return;
 
 	for (i = 0U; i < self->aq_vecs; i++) {
 		aq_vec = self->aq_vec[i];
@@ -1441,13 +1441,14 @@ void aq_nic_deinit(struct aq_nic_s *self, bool link_down)
 	aq_ptp_ring_free(self);
 	aq_ptp_free(self);
 
-	if (likely(self->aq_fw_ops->deinit) && link_down) {
-		mutex_lock(&self->fwreq_mutex);
-		self->aq_fw_ops->deinit(self->aq_hw);
-		mutex_unlock(&self->fwreq_mutex);
+	/* May be invoked during hot unplug. */
+	if (pci_device_is_present(self->pdev)) {
+		if (likely(self->aq_fw_ops->deinit) && link_down) {
+			mutex_lock(&self->fwreq_mutex);
+			self->aq_fw_ops->deinit(self->aq_hw);
+			mutex_unlock(&self->fwreq_mutex);
+		}
 	}
-
-err_exit:;
 }
 
 void aq_nic_free_vectors(struct aq_nic_s *self)
-- 
2.43.0