[PATCH] net: mvneta_bm: add suspend/resume to prevent crash after resume

[Yun Zhou <yun.zhou@windriver.com>]

The mvneta driver uses the hardware Buffer Manager (BM) for RX buffer
allocation. During suspend, mvneta disables its clock, causing BM to
lose all buffer address state. On resume, mvneta_bm_port_init() re-
attaches the BM pool to the NIC, but BM hardware returns stale/garbage
buffer addresses. When NAPI poll processes these buffers, DMA cache
sync hits an invalid virtual address causing a kernel panic:

  Unable to handle kernel paging request at virtual address b0000080
  PC is at v7_dma_inv_range
  Call trace:
   v7_dma_inv_range from arch_sync_dma_for_cpu+0x94/0x158
   arch_sync_dma_for_cpu from __dma_sync_single_for_cpu+0xc4/0x15c
   __dma_sync_single_for_cpu from mvneta_rx_swbm+0x6c8/0xf48
   mvneta_rx_swbm from mvneta_poll+0x6fc/0x70c
   mvneta_poll from __napi_poll.constprop.0+0x2c/0x1e0
   __napi_poll.constprop.0 from net_rx_action+0x160/0x2c4
   net_rx_action from handle_softirqs+0xd8/0x2b8
   handle_softirqs from run_ksoftirqd+0x30/0x94
   run_ksoftirqd from smpboot_thread_fn+0x100/0x204
   smpboot_thread_fn from kthread+0xf4/0x110
   kthread from ret_from_fork+0x14/0x28

Fix by adding suspend/resume callbacks to the BM driver:
- suspend: stop BM unit and disable clock
- resume: enable clock, reinitialize BM defaults and restart pools

Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
---
 drivers/net/ethernet/marvell/mvneta_bm.c | 25 ++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/net/ethernet/marvell/mvneta_bm.c b/drivers/net/ethernet/marvell/mvneta_bm.c
index 6bb380494919..a0800b99c007 100644
--- a/drivers/net/ethernet/marvell/mvneta_bm.c
+++ b/drivers/net/ethernet/marvell/mvneta_bm.c
@@ -477,6 +477,30 @@ static void mvneta_bm_remove(struct platform_device *pdev)
 	clk_disable_unprepare(priv->clk);
 }
 
+#ifdef CONFIG_PM_SLEEP
+static int mvneta_bm_suspend(struct device *dev)
+{
+	struct mvneta_bm *priv = dev_get_drvdata(dev);
+
+	mvneta_bm_write(priv, MVNETA_BM_COMMAND_REG, MVNETA_BM_STOP_MASK);
+	clk_disable_unprepare(priv->clk);
+	return 0;
+}
+
+static int mvneta_bm_resume(struct device *dev)
+{
+	struct mvneta_bm *priv = dev_get_drvdata(dev);
+
+	clk_prepare_enable(priv->clk);
+	mdelay(1);
+	mvneta_bm_default_set(priv);
+	mvneta_bm_pools_init(priv);
+	return 0;
+}
+#endif
+
+static SIMPLE_DEV_PM_OPS(mvneta_bm_pm_ops, mvneta_bm_suspend, mvneta_bm_resume);
+
 static const struct of_device_id mvneta_bm_match[] = {
 	{ .compatible = "marvell,armada-380-neta-bm" },
 	{ }
@@ -489,6 +513,7 @@ static struct platform_driver mvneta_bm_driver = {
 	.driver = {
 		.name = MVNETA_BM_DRIVER_NAME,
 		.of_match_table = mvneta_bm_match,
+		.pm = &mvneta_bm_pm_ops,
 	},
 };
 
-- 
2.43.0