According to the report of [1], this driver is possible to cause the following error in ravb_tx_timeout_work(). ravb e6800000.ethernet ethernet: failed to switch device to config mode This error means that the hardware could not change the state from "Operation" to "Configuration" while some tx and/or rx queue are operating. After that, ravb_config() in ravb_dmac_init() will fail, and then any descriptors will be not allocaled anymore so that NULL pointer dereference happens after that on ravb_start_xmit(). To fix the issue, the ravb_tx_timeout_work() should check the return values of ravb_stop_dma() and ravb_dmac_init(). If ravb_stop_dma() fails, ravb_tx_timeout_work() re-enables TX and RX and just exits. If ravb_dmac_init() fails, just exits. [1] https://lore.kernel.org/linux-renesas-soc/20200518045452.2390-1-dirk.behme@xxxxxxxxxxxx/ Reported-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx> Reviewed-by: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxx> --- Changes from RFC v2: - Check the return value of ravb_init_dmac() too. - Update the subject and description. - Fix the comment in the code. - Add Reviewed-by Sergei. https://patchwork.kernel.org/patch/11673621/ Changes from RFC v1: - Check the return value of ravb_stop_dma() and exit if the hardware condition can not be initialized in the tx timeout. - Update the commit subject and description. - Fix some typo. https://patchwork.kernel.org/patch/11570217/ Unfortunately, I still didn't reproduce the issue yet. But, I got review from Sergei in v2. So, I removed RFC on this patch. drivers/net/ethernet/renesas/ravb_main.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c index a442bcf6..99f7aae 100644 --- a/drivers/net/ethernet/renesas/ravb_main.c +++ b/drivers/net/ethernet/renesas/ravb_main.c @@ -1450,6 +1450,7 @@ static void ravb_tx_timeout_work(struct work_struct *work) struct ravb_private *priv = container_of(work, struct ravb_private, work); struct net_device *ndev = priv->ndev; + int error; netif_tx_stop_all_queues(ndev); @@ -1458,15 +1459,36 @@ static void ravb_tx_timeout_work(struct work_struct *work) ravb_ptp_stop(ndev); /* Wait for DMA stopping */ - ravb_stop_dma(ndev); + if (ravb_stop_dma(ndev)) { + /* If ravb_stop_dma() fails, the hardware is still operating + * for TX and/or RX. So, this should not call the following + * functions because ravb_dmac_init() is possible to fail too. + * Also, this should not retry ravb_stop_dma() again and again + * here because it's possible to wait forever. So, this just + * re-enables the TX and RX and skip the following + * re-initialization procedure. + */ + ravb_rcv_snd_enable(ndev); + goto out; + } ravb_ring_free(ndev, RAVB_BE); ravb_ring_free(ndev, RAVB_NC); /* Device init */ - ravb_dmac_init(ndev); + error = ravb_dmac_init(ndev); + if (error) { + /* If ravb_dmac_init() fails, descriptors are freed. So, this + * should return here to avoid re-enabling the TX and RX in + * ravb_emac_init(). + */ + netdev_err(ndev, "%s: ravb_dmac_init() failed, error %d\n", + __func__, error); + return; + } ravb_emac_init(ndev); +out: /* Initialise PTP Clock driver */ if (priv->chip_id == RCAR_GEN2) ravb_ptp_init(ndev, priv->pdev); -- 2.7.4
