net: designware: set the PS bit when resetting DMA bus in MII configuration
On the SPEAr600 SoC, which has the dwmac1000 variant of the IP block,
the DMA reset never succeeds when a MII PHY is used (no problem with a
GMII PHY). The designware_eth_init() function sets the
DMAMAC_SRST bit in the DMA_BUS_MODE register, and then
polls until this bit clears. When a MII PHY is used, with the current
driver, this bit never clears and the driver therefore doesn't work.
The reason is that the PS bit of the GMAC_CONTROL register should be
correctly configured for the DMA reset to work. When the PS bit is 0,
it tells the MAC we have a GMII PHY, when the PS bit is 1, it tells
the MAC we have a MII PHY.
Doing a DMA reset clears all registers, so the PS bit is cleared as
well. This makes the DMA reset work fine with a GMII PHY. However,
with MII PHY, the PS bit should be set.
We have identified this issue thanks to two SPEAr600 platform:
- One equipped with a GMII PHY, with which the existing driver was
working fine.
- One equipped with a MII PHY, where the current driver fails because
the DMA reset times out.
Note: Taken from https://www.spinics.net/lists/netdev/msg432578.html
Signed-off-by: Quentin Schulz <quentin.schulz@bootlin.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/drivers/net/designware.c b/drivers/net/designware.c
index cf12521..10a8709 100644
--- a/drivers/net/designware.c
+++ b/drivers/net/designware.c
@@ -280,6 +280,15 @@
writel(readl(&dma_p->busmode) | DMAMAC_SRST, &dma_p->busmode);
+ /*
+ * When a MII PHY is used, we must set the PS bit for the DMA
+ * reset to succeed.
+ */
+ if (priv->phydev->interface == PHY_INTERFACE_MODE_MII)
+ writel(readl(&mac_p->conf) | MII_PORTSELECT, &mac_p->conf);
+ else
+ writel(readl(&mac_p->conf) & ~MII_PORTSELECT, &mac_p->conf);
+
start = get_timer(0);
while (readl(&dma_p->busmode) & DMAMAC_SRST) {
if (get_timer(start) >= CONFIG_MACRESET_TIMEOUT) {