arm: Kirkwood: Fix compiler optimization bug for kwgbe_send

kwgbe_send/recv both have loops waiting for the hardware to set  a bit.
GCC 4.3.3 cleverly optimizes the send case to ... a while(1); loop. This
patch uses readl to force a read from device memory. Other volatile
accesses have also been replaced with readl/writel where appropriate
(as per suggestions on the U-boot mailing list).

Signed-off-by: Simon Kagstrom <simon.kagstrom@netinsight.net>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>

diff --git a/drivers/net/kirkwood_egiga.c b/drivers/net/kirkwood_egiga.c
index 3c5db19cb084fce8ad98505cbf9e5ce685c29ab3..77c7a840cfc3041b23178b57002d1791cfc3aed5 100644 (file)
--- a/drivers/net/kirkwood_egiga.c
+++ b/drivers/net/kirkwood_egiga.c
@@ -49,7 +49,7 @@ static int smi_reg_read(char *devname, u8 phy_adr, u8 reg_ofs, u16 * data)
        struct kwgbe_device *dkwgbe = to_dkwgbe(dev);
        struct kwgbe_registers *regs = dkwgbe->regs;
        u32 smi_reg;
-       volatile u32 timeout;
+       u32 timeout;
 
        /* Phyadr read request */
        if (phy_adr == 0xEE && reg_ofs == 0xEE) {
@@ -124,7 +124,7 @@ static int smi_reg_write(char *devname, u8 phy_adr, u8 reg_ofs, u16 data)
        struct kwgbe_device *dkwgbe = to_dkwgbe(dev);
        struct kwgbe_registers *regs = dkwgbe->regs;
        u32 smi_reg;
-       volatile u32 timeout;
+       u32 timeout;
 
        /* Phyadr write request*/
        if (phy_adr == 0xEE && reg_ofs == 0xEE) {
@@ -370,7 +370,7 @@ static void port_uc_addr_set(struct kwgbe_registers *regs, u8 * p_addr)
  */
 static void kwgbe_init_rx_desc_ring(struct kwgbe_device *dkwgbe)
 {
-       volatile struct kwgbe_rxdesc *p_rx_desc;
+       struct kwgbe_rxdesc *p_rx_desc;
        int i;
 
        /* initialize the Rx descriptors ring */
@@ -487,6 +487,7 @@ static int kwgbe_send(struct eth_device *dev, volatile void *dataptr,
        struct kwgbe_device *dkwgbe = to_dkwgbe(dev);
        struct kwgbe_registers *regs = dkwgbe->regs;
        struct kwgbe_txdesc *p_txdesc = dkwgbe->p_txdesc;
+       u32 cmd_sts;
 
        if ((u32) dataptr & 0x07) {
                printf("Err..(%s) xmit dataptr not 64bit aligned\n",
@@ -507,21 +508,24 @@ static int kwgbe_send(struct eth_device *dev, volatile void *dataptr,
        /*
         * wait for packet xmit completion
         */
-       while (p_txdesc->cmd_sts & KWGBE_BUFFER_OWNED_BY_DMA) {
+       cmd_sts = readl(&p_txdesc->cmd_sts);
+       while (cmd_sts & KWGBE_BUFFER_OWNED_BY_DMA) {
                /* return fail if error is detected */
-               if (p_txdesc->cmd_sts & (KWGBE_UR_ERROR | KWGBE_RL_ERROR)) {
+               if (cmd_sts & (KWGBE_UR_ERROR | KWGBE_RL_ERROR)) {
                        printf("Err..(%s) in xmit packet\n", __FUNCTION__);
                        return -1;
                }
+               cmd_sts = readl(&p_txdesc->cmd_sts);
        };
        return 0;
 }
 
 static int kwgbe_recv(struct eth_device *dev)
 {
-       volatile struct kwgbe_device *dkwgbe = to_dkwgbe(dev);
-       volatile struct kwgbe_rxdesc *p_rxdesc_curr = dkwgbe->p_rxdesc_curr;
-       volatile u32 timeout = 0;
+       struct kwgbe_device *dkwgbe = to_dkwgbe(dev);
+       struct kwgbe_rxdesc *p_rxdesc_curr = dkwgbe->p_rxdesc_curr;
+       u32 cmd_sts;
+       u32 timeout = 0;
 
        /* wait untill rx packet available or timeout */
        do {
@@ -531,7 +535,7 @@ static int kwgbe_recv(struct eth_device *dev)
                        debug("%s time out...\n", __FUNCTION__);
                        return -1;
                }
-       } while (p_rxdesc_curr->cmd_sts & KWGBE_BUFFER_OWNED_BY_DMA);
+       } while (readl(&p_rxdesc_curr->cmd_sts) & KWGBE_BUFFER_OWNED_BY_DMA);
 
        if (p_rxdesc_curr->byte_cnt != 0) {
                debug("%s: Received %d byte Packet @ 0x%x (cmd_sts= %08x)\n",
@@ -545,14 +549,16 @@ static int kwgbe_recv(struct eth_device *dev)
         * OR the error summary bit is on,
         * the packets needs to be dropeed.
         */
-       if ((p_rxdesc_curr->cmd_sts &
+       cmd_sts = readl(&p_rxdesc_curr->cmd_sts);
+
+       if ((cmd_sts &
                (KWGBE_RX_FIRST_DESC | KWGBE_RX_LAST_DESC))
                != (KWGBE_RX_FIRST_DESC | KWGBE_RX_LAST_DESC)) {
 
                printf("Err..(%s) Dropping packet spread on"
                        " multiple descriptors\n", __FUNCTION__);
 
-       } else if (p_rxdesc_curr->cmd_sts & KWGBE_ERROR_SUMMARY) {
+       } else if (cmd_sts & KWGBE_ERROR_SUMMARY) {
 
                printf("Err..(%s) Dropping packet with errors\n",
                        __FUNCTION__);
@@ -574,7 +580,8 @@ static int kwgbe_recv(struct eth_device *dev)
        p_rxdesc_curr->buf_size = PKTSIZE_ALIGN;
        p_rxdesc_curr->byte_cnt = 0;
 
-       dkwgbe->p_rxdesc_curr = p_rxdesc_curr->nxtdesc_p;
+       writel((unsigned)p_rxdesc_curr->nxtdesc_p, &dkwgbe->p_rxdesc_curr);
+
        return 0;
 }