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writing
WR_OSR_LMT and RD_OSR_LMT have a reset value of 1.
Since the reset value wasn't cleared before writing, the value in the
register would be incorrect if specifying an uneven value for
snps,wr_osr_lmt/snps,rd_osr_lmt.
Zero is a valid value for the properties, since the databook specifies:
maximum outstanding requests = WR_OSR_LMT + 1.
We do not want to change the behavior for existing users when the
property is missing. Therefore, default to 1 if the property is missing,
since that is the same as the reset value.
Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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The dwmac4 IP can synthesized with 1-8 number of tx queues.
On an IP synthesized with DWC_EQOS_NUM_TXQ > 1, all txqueues are disabled
by default. For these IPs, the bitfield TXQEN is R/W.
Always enable tx queue 0. The write will have no effect on IPs synthesized
with DWC_EQOS_NUM_TXQ == 1.
The driver does still not utilize more than one tx queue in the IP.
Signed-off-by: Niklas Cassel <niklas.cassel@axis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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DMA behavior is linked to descriptor management:
-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.
Up to 8 DMA could be use but currently we only use one (channel0)
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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