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Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms and conditions of the gnu general public license
version 2 as published by the free software foundation
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 101 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190531190113.822954939@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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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>
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One of main changes of GMAC 4.xx IP is descriptors management.
-descriptors are only used in ring mode.
-A descriptor is composed of 4 32bits registers (no more extended
descriptors)
-descriptor mechanism (Tx for example, but it is exactly the same for RX):
-useful registers:
-DMA_CH#_TxDesc_Ring_Len: length of transmit descriptor
ring
-DMA_CH#_TxDesc_List_Address: start address of the ring
-DMA_CH#_TxDesc_Tail_Pointer: address of the last
descriptor to send + 1.
-DMA_CH#_TxDesc_Current_App_TxDesc: address of the current
descriptor
-The descriptor Tail Pointer register contains the pointer to the
descriptor address (N). The base address and the current
descriptor decide the address of the current descriptor that the
DMA can process. The descriptors up to one location less than the
one indicated by the descriptor tail pointer (N-1) are owned by
the DMA. The DMA continues to process the descriptors until the
following condition occurs:
"current descriptor pointer == Descriptor Tail pointer"
Then the DMA goes into suspend mode. The application must perform
a write to descriptor tail pointer register and update the tail
pointer to have the following condition and to start a new
transfer:
"current descriptor pointer < Descriptor tail pointer"
The DMA automatically wraps around the base address when the end
of ring is reached.
-New features are available on IP:
-TSO (TCP Segmentation Offload) for TX only
-Split header: to have header and payload in 2 different buffers
Signed-off-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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