ag71xx: fix memory corruption issues on ar7240 on ethernet start/stop

When the DMA engine state gets corrupted due to a hardware issues, it
often won't stop rx until a full reset is issued. In that case the hardware
must keep a valid descriptor, otherwise it will write to random places in
system RAM, triggering random crashes. To fix this, keep a dummy descriptor
without a buffer that keeps the DMA engine in a sane state until the reset
is done

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@27895 3c298f89-4303-0410-b956-a3cf2f4a3e73

diff --git a/target/linux/ar71xx/files/drivers/net/ag71xx/ag71xx.h b/target/linux/ar71xx/files/drivers/net/ag71xx/ag71xx.h
index 1025bb4..9dcbf4a 100644 (file)
--- a/target/linux/ar71xx/files/drivers/net/ag71xx/ag71xx.h
+++ b/target/linux/ar71xx/files/drivers/net/ag71xx/ag71xx.h
@@ -148,6 +148,9 @@ struct ag71xx {
        struct napi_struct      napi;
        u32                     msg_enable;
 
+       struct ag71xx_desc      *stop_desc;
+       dma_addr_t              stop_desc_dma;
+
        struct ag71xx_ring      rx_ring;
        struct ag71xx_ring      tx_ring;
 

diff --git a/target/linux/ar71xx/files/drivers/net/ag71xx/ag71xx_main.c b/target/linux/ar71xx/files/drivers/net/ag71xx/ag71xx_main.c
index 1f9cdf3..9bfaa82 100644 (file)
--- a/target/linux/ar71xx/files/drivers/net/ag71xx/ag71xx_main.c
+++ b/target/linux/ar71xx/files/drivers/net/ag71xx/ag71xx_main.c
@@ -374,8 +374,8 @@ static void ag71xx_dma_reset(struct ag71xx *ag)
        mdelay(1);
 
        /* clear descriptor addresses */
-       ag71xx_wr(ag, AG71XX_REG_TX_DESC, 0);
-       ag71xx_wr(ag, AG71XX_REG_RX_DESC, 0);
+       ag71xx_wr(ag, AG71XX_REG_TX_DESC, ag->stop_desc_dma);
+       ag71xx_wr(ag, AG71XX_REG_RX_DESC, ag->stop_desc_dma);
 
        /* clear pending RX/TX interrupts */
        for (i = 0; i < 256; i++) {
@@ -1085,6 +1085,16 @@ static int __devinit ag71xx_probe(struct platform_device *pdev)
        ag->tx_ring.size = AG71XX_TX_RING_SIZE_DEFAULT;
        ag->rx_ring.size = AG71XX_RX_RING_SIZE_DEFAULT;
 
+       ag->stop_desc = dma_alloc_coherent(NULL,
+               sizeof(struct ag71xx_desc), &ag->stop_desc_dma, GFP_KERNEL);
+
+       if (!ag->stop_desc)
+               goto err_free_irq;
+
+       ag->stop_desc->data = 0;
+       ag->stop_desc->ctrl = 0;
+       ag->stop_desc->next = (u32) ag->stop_desc_dma;
+
        memcpy(dev->dev_addr, pdata->mac_addr, ETH_ALEN);
 
        netif_napi_add(dev, &ag->napi, ag71xx_poll, AG71XX_NAPI_WEIGHT);
@@ -1092,7 +1102,7 @@ static int __devinit ag71xx_probe(struct platform_device *pdev)
        err = register_netdev(dev);
        if (err) {
                dev_err(&pdev->dev, "unable to register net device\n");
-               goto err_free_irq;
+               goto err_free_desc;
        }
 
        printk(KERN_INFO "%s: Atheros AG71xx at 0x%08lx, irq %d\n",
@@ -1120,6 +1130,9 @@ err_phy_disconnect:
        ag71xx_phy_disconnect(ag);
 err_unregister_netdev:
        unregister_netdev(dev);
+err_free_desc:
+       dma_free_coherent(NULL, sizeof(struct ag71xx_desc), ag->stop_desc,
+                         ag->stop_desc_dma);
 err_free_irq:
        free_irq(dev->irq, dev);
 err_unmap_mii_ctrl: