stmmac: add Rx watchdog support to mitigate the DMA irqs

GMAC devices newer than databook 3.40 has an embedded timer
that can be used for mitigating the number of interrupts.
So this patch adds this optimizations.

At any rate, the Rx watchdog can be disable (on bugged HW) by
passing from the platform the riwt_off field.

In this implementation the rx timer stored in the Reg9 is fixed
to the max value. This will be tuned by using ethtool.

V2: added a platform parameter to force to disable the rx-watchdog
for example on new core where it is bugged.

V3: do not disable NAPI when Rx watchdog is used.

V4: a new extra statistic field has been added to show the early
receive status in the interrupt handler.
This patch also adds an extra check to avoid to call
napi_schedule when the DMA_INTR_ENA_RIE bit is disabled in the
Interrupt Mask register.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c
index 033500090f55..bf83c03bfd06 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_dma.c
@@ -174,6 +174,11 @@ static unsigned int dwmac1000_get_hw_feature(void __iomem *ioaddr)
 	return readl(ioaddr + DMA_HW_FEATURE);
 }
 
+static void dwmac1000_rx_watchdog(void __iomem *ioaddr, u32 riwt)
+{
+	writel(riwt, ioaddr + DMA_RX_WATCHDOG);
+}
+
 const struct stmmac_dma_ops dwmac1000_dma_ops = {
 	.init = dwmac1000_dma_init,
 	.dump_regs = dwmac1000_dump_dma_regs,
@@ -187,4 +192,5 @@ const struct stmmac_dma_ops dwmac1000_dma_ops = {
 	.stop_rx = dwmac_dma_stop_rx,
 	.dma_interrupt = dwmac_dma_interrupt,
 	.get_hw_feature = dwmac1000_get_hw_feature,
+	.rx_watchdog = dwmac1000_rx_watchdog,
 };