net: ti: icssg-prueth: Fix buffer allocation for ICSSG

Fixes overlapping buffer allocation for ICSSG peripheral
used for storing packets to be received/transmitted.
There are 3 buffers:
1. Buffer for Locally Injected Packets
2. Buffer for Forwarding Packets
3. Buffer for Host Egress Packets

In existing allocation buffers for 2. and 3. are overlapping causing
packet corruption.

Packet corruption observations:
During tcp iperf testing, due to overlapping buffers the received ack
packet overwrites the packet to be transmitted. So, we see packets on
wire with the ack packet content inside the content of next TCP packet
from sender device.

Details for AM64x switch mode:
-> Allocation by existing driver:
+---------+-------------------------------------------------------------+
|         |          SLICE 0             |          SLICE 1             |
|         +------+--------------+--------+------+--------------+--------+
|         | Slot | Base Address | Size   | Slot | Base Address | Size   |
|---------+------+--------------+--------+------+--------------+--------+
|         | 0    | 70000000     | 0x2000 | 0    | 70010000     | 0x2000 |
|         | 1    | 70002000     | 0x2000 | 1    | 70012000     | 0x2000 |
|         | 2    | 70004000     | 0x2000 | 2    | 70014000     | 0x2000 |
| FWD     | 3    | 70006000     | 0x2000 | 3    | 70016000     | 0x2000 |
| Buffers | 4    | 70008000     | 0x2000 | 4    | 70018000     | 0x2000 |
|         | 5    | 7000A000     | 0x2000 | 5    | 7001A000     | 0x2000 |
|         | 6    | 7000C000     | 0x2000 | 6    | 7001C000     | 0x2000 |
|         | 7    | 7000E000     | 0x2000 | 7    | 7001E000     | 0x2000 |
+---------+------+--------------+--------+------+--------------+--------+
|         | 8    | 70020000     | 0x1000 | 8    | 70028000     | 0x1000 |
|         | 9    | 70021000     | 0x1000 | 9    | 70029000     | 0x1000 |
|         | 10   | 70022000     | 0x1000 | 10   | 7002A000     | 0x1000 |
| Our     | 11   | 70023000     | 0x1000 | 11   | 7002B000     | 0x1000 |
| LI      | 12   | 00000000     | 0x0    | 12   | 00000000     | 0x0    |
| Buffers | 13   | 00000000     | 0x0    | 13   | 00000000     | 0x0    |
|         | 14   | 00000000     | 0x0    | 14   | 00000000     | 0x0    |
|         | 15   | 00000000     | 0x0    | 15   | 00000000     | 0x0    |
+---------+------+--------------+--------+------+--------------+--------+
|         | 16   | 70024000     | 0x1000 | 16   | 7002C000     | 0x1000 |
|         | 17   | 70025000     | 0x1000 | 17   | 7002D000     | 0x1000 |
|         | 18   | 70026000     | 0x1000 | 18   | 7002E000     | 0x1000 |
| Their   | 19   | 70027000     | 0x1000 | 19   | 7002F000     | 0x1000 |
| LI      | 20   | 00000000     | 0x0    | 20   | 00000000     | 0x0    |
| Buffers | 21   | 00000000     | 0x0    | 21   | 00000000     | 0x0    |
|         | 22   | 00000000     | 0x0    | 22   | 00000000     | 0x0    |
|         | 23   | 00000000     | 0x0    | 23   | 00000000     | 0x0    |
+---------+------+--------------+--------+------+--------------+--------+
--> here 16, 17, 18, 19 overlapping with below express buffer

+-----+-----------------------------------------------+
|     |       SLICE 0       |        SLICE 1          |
|     +------------+----------+------------+----------+
|     | Start addr | End addr | Start addr | End addr |
+-----+------------+----------+------------+----------+
| EXP | 70024000   | 70028000 | 7002C000   | 70030000 | <-- Overlapping
| PRE | 70030000   | 70033800 | 70034000   | 70037800 |
+-----+------------+----------+------------+----------+

+---------------------+----------+----------+
|                     | SLICE 0  |  SLICE 1 |
+---------------------+----------+----------+
| Default Drop Offset | 00000000 | 00000000 |     <-- Field not configured
+---------------------+----------+----------+

-> Allocation this patch brings:
+---------+-------------------------------------------------------------+
|         |          SLICE 0             |          SLICE 1             |
|         +------+--------------+--------+------+--------------+--------+
|         | Slot | Base Address | Size   | Slot | Base Address | Size   |
|---------+------+--------------+--------+------+--------------+--------+
|         | 0    | 70000000     | 0x2000 | 0    | 70040000     | 0x2000 |
|         | 1    | 70002000     | 0x2000 | 1    | 70042000     | 0x2000 |
|         | 2    | 70004000     | 0x2000 | 2    | 70044000     | 0x2000 |
| FWD     | 3    | 70006000     | 0x2000 | 3    | 70046000     | 0x2000 |
| Buffers | 4    | 70008000     | 0x2000 | 4    | 70048000     | 0x2000 |
|         | 5    | 7000A000     | 0x2000 | 5    | 7004A000     | 0x2000 |
|         | 6    | 7000C000     | 0x2000 | 6    | 7004C000     | 0x2000 |
|         | 7    | 7000E000     | 0x2000 | 7    | 7004E000     | 0x2000 |
+---------+------+--------------+--------+------+--------------+--------+
|         | 8    | 70010000     | 0x1000 | 8    | 70050000     | 0x1000 |
|         | 9    | 70011000     | 0x1000 | 9    | 70051000     | 0x1000 |
|         | 10   | 70012000     | 0x1000 | 10   | 70052000     | 0x1000 |
| Our     | 11   | 70013000     | 0x1000 | 11   | 70053000     | 0x1000 |
| LI      | 12   | 00000000     | 0x0    | 12   | 00000000     | 0x0    |
| Buffers | 13   | 00000000     | 0x0    | 13   | 00000000     | 0x0    |
|         | 14   | 00000000     | 0x0    | 14   | 00000000     | 0x0    |
|         | 15   | 00000000     | 0x0    | 15   | 00000000     | 0x0    |
+---------+------+--------------+--------+------+--------------+--------+
|         | 16   | 70014000     | 0x1000 | 16   | 70054000     | 0x1000 |
|         | 17   | 70015000     | 0x1000 | 17   | 70055000     | 0x1000 |
|         | 18   | 70016000     | 0x1000 | 18   | 70056000     | 0x1000 |
| Their   | 19   | 70017000     | 0x1000 | 19   | 70057000     | 0x1000 |
| LI      | 20   | 00000000     | 0x0    | 20   | 00000000     | 0x0    |
| Buffers | 21   | 00000000     | 0x0    | 21   | 00000000     | 0x0    |
|         | 22   | 00000000     | 0x0    | 22   | 00000000     | 0x0    |
|         | 23   | 00000000     | 0x0    | 23   | 00000000     | 0x0    |
+---------+------+--------------+--------+------+--------------+--------+

+-----+-----------------------------------------------+
|     |       SLICE 0       |        SLICE 1          |
|     +------------+----------+------------+----------+
|     | Start addr | End addr | Start addr | End addr |
+-----+------------+----------+------------+----------+
| EXP | 70018000   | 7001C000 | 70058000   | 7005C000 |
| PRE | 7001C000   | 7001F800 | 7005C000   | 7005F800 |
+-----+------------+----------+------------+----------+

+---------------------+----------+----------+
|                     | SLICE 0  |  SLICE 1 |
+---------------------+----------+----------+
| Default Drop Offset | 7001F800 | 7005F800 |
+---------------------+----------+----------+

Rootcause: missing buffer configuration for Express frames in
function: prueth_fw_offload_buffer_setup()

Details:
Driver implements two distinct buffer configuration functions that are
invoked based on the driver state and ICSSG firmware:-
- prueth_fw_offload_buffer_setup()
- prueth_emac_buffer_setup()

During initialization, driver creates standard network interfaces
(netdevs) and configures buffers via prueth_emac_buffer_setup().
This function properly allocates and configures all required memory
regions including:
- LI buffers
- Express packet buffers
- Preemptible packet buffers

However, when the driver transitions to an offload mode (switch/HSR/PRP),
buffer reconfiguration is handled by prueth_fw_offload_buffer_setup().
This function does not reconfigure the buffer regions required for
Express packets, leading to incorrect buffer allocation.

Fixes: abd5576b ("net: ti: icssg-prueth: Add support for ICSSG switch firmware")
Signed-off-by: Himanshu Mittal <h-mittal1@ti.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250717094220.546388-1-h-mittal1@ti.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>