[PATCH v2] net: mvneta_bm: add suspend/resume support 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: drain all buffers (with DMA unmapping), free the BPPE
  regions, and reset pool state to FREE before stopping BM and gating
  the clock.

- resume: enable the clock and reinitialize BM defaults. Pool
  allocation and buffer refill are handled by mvneta_resume() through
  the normal mvneta_bm_port_init() path, which sees pools as FREE and
  performs full initialization identical to probe.

Add a device_link (DL_FLAG_AUTOREMOVE_CONSUMER) in mvneta_probe to
guarantee BM resumes before mvneta and suspends after mvneta.

Signed-off-by: Yun Zhou <yun.zhou@windriver.com>
---
v2:
  - Drain buffers via mvneta_bm_bufs_free() in suspend instead of only
    stopping BM and gating the clock. This ensures proper DMA unmapping
    and avoids buffer leaks.
  - Free the BPPE DMA-coherent region in suspend so that resume takes
    the full probe-time initialization path (alloc + fill), eliminating
    the need to modify mvneta_bm_pool_create().
  - Reset pool type to MVNETA_BM_FREE in suspend so mvneta_bm_pool_use()
    correctly re-creates and refills pools on resume.
  - Check clk_prepare_enable() return value in resume.
  - Add device_link between mvneta (consumer) and mvneta_bm (supplier)
    to guarantee correct suspend/resume ordering.

 drivers/net/ethernet/marvell/mvneta.c    |  5 +++
 drivers/net/ethernet/marvell/mvneta_bm.c | 47 ++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index 0c061fb0ed07..cfaf5ea1db9e 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -5678,6 +5678,11 @@ static int mvneta_probe(struct platform_device *pdev)
 					 "use SW buffer management\n");
 				mvneta_bm_put(pp->bm_priv);
 				pp->bm_priv = NULL;
+			} else {
+				/* Ensure BM suspends after us, resumes before us */
+				device_link_add(&pdev->dev,
+						&pp->bm_priv->pdev->dev,
+						DL_FLAG_AUTOREMOVE_CONSUMER);
 			}
 		}
 		/* Set RX packet offset correction for platforms, whose
diff --git a/drivers/net/ethernet/marvell/mvneta_bm.c b/drivers/net/ethernet/marvell/mvneta_bm.c
index 6bb380494919..ff2fe4020a45 100644
--- a/drivers/net/ethernet/marvell/mvneta_bm.c
+++ b/drivers/net/ethernet/marvell/mvneta_bm.c
@@ -477,6 +477,52 @@ 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);
+	int i;
+
+	/* Drain buffers and free pool resources while BM is still clocked */
+	for (i = 0; i < MVNETA_BM_POOLS_NUM; i++) {
+		struct mvneta_bm_pool *bm_pool = &priv->bm_pools[i];
+		int size_bytes;
+
+		if (bm_pool->type == MVNETA_BM_FREE)
+			continue;
+
+		mvneta_bm_bufs_free(priv, bm_pool, bm_pool->port_map);
+
+		size_bytes = sizeof(u32) * bm_pool->hwbm_pool.size;
+		dma_free_coherent(&priv->pdev->dev, size_bytes,
+				  bm_pool->virt_addr, bm_pool->phys_addr);
+		bm_pool->virt_addr = NULL;
+		bm_pool->type = MVNETA_BM_FREE;
+	}
+
+	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);
+	int err;
+
+	err = clk_prepare_enable(priv->clk);
+	if (err)
+		return err;
+
+	/* Reinitialize BM hardware; pools are refilled by mvneta_resume() */
+	mvneta_bm_default_set(priv);
+	mvneta_bm_write(priv, MVNETA_BM_COMMAND_REG, MVNETA_BM_START_MASK);
+	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 +535,7 @@ 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