On the AST2600 care must be taken to ensure writes appear correctly when
modifying the interrupt reglated registers.

Add a function to perform a read after all writes to the IER and ISR registers.

Fixes: 39bfab8844a0 ("net: ftgmac100: Add support for DT phy-handle property")
Signed-off-by: Dylan Hung <dylan_h...@aspeedtech.com>
Signed-off-by: Joel Stanley <j...@jms.id.au>
---
 drivers/net/ethernet/faraday/ftgmac100.c | 38 ++++++++++++------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/drivers/net/ethernet/faraday/ftgmac100.c 
b/drivers/net/ethernet/faraday/ftgmac100.c
index 810bda80f138..0c67fc3e27df 100644
--- a/drivers/net/ethernet/faraday/ftgmac100.c
+++ b/drivers/net/ethernet/faraday/ftgmac100.c
@@ -111,6 +111,14 @@ struct ftgmac100 {
        bool is_aspeed;
 };
 
+/* Helper to ensure writes are observed with the correct ordering. Use only
+ * for IER and ISR accesses. */
+static void ftgmac100_write(u32 val, void __iomem *addr)
+{
+       iowrite32(val, addr);
+       ioread32(addr);
+}
+
 static int ftgmac100_reset_mac(struct ftgmac100 *priv, u32 maccr)
 {
        struct net_device *netdev = priv->netdev;
@@ -1048,7 +1056,7 @@ static void ftgmac100_adjust_link(struct net_device 
*netdev)
                return;
 
        /* Disable all interrupts */
-       iowrite32(0, priv->base + FTGMAC100_OFFSET_IER);
+       ftgmac100_write(0, priv->base + FTGMAC100_OFFSET_IER);
 
        /* Reset the adapter asynchronously */
        schedule_work(&priv->reset_task);
@@ -1246,7 +1254,7 @@ static irqreturn_t ftgmac100_interrupt(int irq, void 
*dev_id)
 
        /* Fetch and clear interrupt bits, process abnormal ones */
        status = ioread32(priv->base + FTGMAC100_OFFSET_ISR);
-       iowrite32(status, priv->base + FTGMAC100_OFFSET_ISR);
+       ftgmac100_write(status, priv->base + FTGMAC100_OFFSET_ISR);
        if (unlikely(status & FTGMAC100_INT_BAD)) {
 
                /* RX buffer unavailable */
@@ -1266,7 +1274,7 @@ static irqreturn_t ftgmac100_interrupt(int irq, void 
*dev_id)
                        if (net_ratelimit())
                                netdev_warn(netdev,
                                           "AHB bus error ! Resetting chip.\n");
-                       iowrite32(0, priv->base + FTGMAC100_OFFSET_IER);
+                       ftgmac100_write(0, priv->base + FTGMAC100_OFFSET_IER);
                        schedule_work(&priv->reset_task);
                        return IRQ_HANDLED;
                }
@@ -1281,7 +1289,7 @@ static irqreturn_t ftgmac100_interrupt(int irq, void 
*dev_id)
        }
 
        /* Only enable "bad" interrupts while NAPI is on */
-       iowrite32(new_mask, priv->base + FTGMAC100_OFFSET_IER);
+       ftgmac100_write(new_mask, priv->base + FTGMAC100_OFFSET_IER);
 
        /* Schedule NAPI bh */
        napi_schedule_irqoff(&priv->napi);
@@ -1320,8 +1328,7 @@ static int ftgmac100_poll(struct napi_struct *napi, int 
budget)
                ftgmac100_start_hw(priv);
 
                /* Re-enable "bad" interrupts */
-               iowrite32(FTGMAC100_INT_BAD,
-                         priv->base + FTGMAC100_OFFSET_IER);
+               ftgmac100_write(FTGMAC100_INT_BAD, priv->base + 
FTGMAC100_OFFSET_IER);
        }
 
        /* As long as we are waiting for transmit packets to be
@@ -1336,13 +1343,7 @@ static int ftgmac100_poll(struct napi_struct *napi, int 
budget)
                 * they were masked. So we clear them first, then we need
                 * to re-check if there's something to process
                 */
-               iowrite32(FTGMAC100_INT_RXTX,
-                         priv->base + FTGMAC100_OFFSET_ISR);
-
-               /* Push the above (and provides a barrier vs. subsequent
-                * reads of the descriptor).
-                */
-               ioread32(priv->base + FTGMAC100_OFFSET_ISR);
+               ftgmac100_write(FTGMAC100_INT_RXTX, priv->base + 
FTGMAC100_OFFSET_ISR);
 
                /* Check RX and TX descriptors for more work to do */
                if (ftgmac100_check_rx(priv) ||
@@ -1353,8 +1354,7 @@ static int ftgmac100_poll(struct napi_struct *napi, int 
budget)
                napi_complete(napi);
 
                /* enable all interrupts */
-               iowrite32(FTGMAC100_INT_ALL,
-                         priv->base + FTGMAC100_OFFSET_IER);
+               ftgmac100_write(FTGMAC100_INT_ALL, priv->base + 
FTGMAC100_OFFSET_IER);
        }
 
        return work_done;
@@ -1382,7 +1382,7 @@ static int ftgmac100_init_all(struct ftgmac100 *priv, 
bool ignore_alloc_err)
        netif_start_queue(priv->netdev);
 
        /* Enable all interrupts */
-       iowrite32(FTGMAC100_INT_ALL, priv->base + FTGMAC100_OFFSET_IER);
+       ftgmac100_write(FTGMAC100_INT_ALL, priv->base + FTGMAC100_OFFSET_IER);
 
        return err;
 }
@@ -1508,7 +1508,7 @@ static int ftgmac100_open(struct net_device *netdev)
  err_irq:
        netif_napi_del(&priv->napi);
  err_hw:
-       iowrite32(0, priv->base + FTGMAC100_OFFSET_IER);
+       ftgmac100_write(0, priv->base + FTGMAC100_OFFSET_IER);
        ftgmac100_free_rings(priv);
        return err;
 }
@@ -1526,7 +1526,7 @@ static int ftgmac100_stop(struct net_device *netdev)
         */
 
        /* disable all interrupts */
-       iowrite32(0, priv->base + FTGMAC100_OFFSET_IER);
+       ftgmac100_write(0, priv->base + FTGMAC100_OFFSET_IER);
 
        netif_stop_queue(netdev);
        napi_disable(&priv->napi);
@@ -1549,7 +1549,7 @@ static void ftgmac100_tx_timeout(struct net_device 
*netdev, unsigned int txqueue
        struct ftgmac100 *priv = netdev_priv(netdev);
 
        /* Disable all interrupts */
-       iowrite32(0, priv->base + FTGMAC100_OFFSET_IER);
+       ftgmac100_write(0, priv->base + FTGMAC100_OFFSET_IER);
 
        /* Do the reset outside of interrupt context */
        schedule_work(&priv->reset_task);
-- 
2.17.1

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