netdev - [PATCH net] net: broadcom: bcm4908_enet: reset DMA rings sw indexes properly

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Date:   Tue, 22 Jun 2021 07:24:15 +0200
From:   Rafał Miłecki <zajec5@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, Florian Fainelli <f.fainelli@...il.com>,
        bcm-kernel-feedback-list@...adcom.com,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Rafał Miłecki <rafal@...ecki.pl>
Subject: [PATCH net] net: broadcom: bcm4908_enet: reset DMA rings sw indexes properly

From: Rafał Miłecki <rafal@...ecki.pl>

Resetting software indexes in bcm4908_dma_alloc_buf_descs() is not
enough as it's called during device probe only. Driver resets DMA on
every .ndo_open callback and it's required to reset indexes then.

This fixes inconsistent rings state and stalled traffic after interface
down & up sequence.

Fixes: 4feffeadbcb2 ("net: broadcom: bcm4908enet: add BCM4908 controller driver")
Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
---
Sorry for a late fix, this bug has been exposed by OpenWrt and debugged
just yesterday.
---
 drivers/net/ethernet/broadcom/bcm4908_enet.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/bcm4908_enet.c b/drivers/net/ethernet/broadcom/bcm4908_enet.c
index 60d908507f51..02a569500234 100644
--- a/drivers/net/ethernet/broadcom/bcm4908_enet.c
+++ b/drivers/net/ethernet/broadcom/bcm4908_enet.c
@@ -174,9 +174,6 @@ static int bcm4908_dma_alloc_buf_descs(struct bcm4908_enet *enet,
 	if (!ring->slots)
 		goto err_free_buf_descs;
 
-	ring->read_idx = 0;
-	ring->write_idx = 0;
-
 	return 0;
 
 err_free_buf_descs:
@@ -304,6 +301,9 @@ static void bcm4908_enet_dma_ring_init(struct bcm4908_enet *enet,
 
 	enet_write(enet, ring->st_ram_block + ENET_DMA_CH_STATE_RAM_BASE_DESC_PTR,
 		   (uint32_t)ring->dma_addr);
+
+	ring->read_idx = 0;
+	ring->write_idx = 0;
 }
 
 static void bcm4908_enet_dma_uninit(struct bcm4908_enet *enet)
-- 
2.26.2