stmmac: fix PTP support for GMAC4

Due to bad management of the descriptors, when use ptp4l,
kernel panics as shown below:
-----------------------------------------------------------
 Unable to handle kernel NULL pointer dereference at virtual
 address 000001ac
 ...
 Internal error: Oops: 17 [#1] SMP ARM
 ...
 Hardware name: STi SoC with Flattened Device Tree
 task: c0c05e80 task.stack: c0c00000
 PC is at dwmac4_wrback_get_tx_timestamp_status+0x0/0xc
 LR is at stmmac_tx_clean+0x2f8/0x4d4
-----------------------------------------------------------

In case of GMAC4 the extended descriptor pointers were
used for getting the timestamp. These are NULL for this HW,
and the normal ones must be used.

The PTP also had problems on this chip due to the bad
register management and issues on the algo adopted to
setup the PTP and getting the timestamp values from the
descriptors.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Acked-by: Rayagond Kokatanur <rayagond@vayavyalabs.com>
Acked-by: Alexandre TORGUE <alexandre.torgue@st.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index b15fc55f1b96..4d2a759b8465 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -129,6 +129,7 @@ struct stmmac_priv {
 	int irq_wake;
 	spinlock_t ptp_lock;
 	void __iomem *mmcaddr;
+	void __iomem *ptpaddr;
 	u32 rx_tail_addr;
 	u32 tx_tail_addr;
 	u32 mss;