Dear Ella,
Well well... That's what I'm currently considering as well: A complete
rewrite of the MAC driver. ST's code is definitely ugly, inconsistent
and often seems to be copy-pasted from older code, but not really
adapted to the new devices/functions.
I already fixed the thing you mentioned by ASSERTing l+q->len to be
smaller than the buffer (ST's driver checks that somehow later by
splitting one buffer into multiple buffers in
ETH_Prepare_Transmit_Descriptors(...), but I'm not sure if that still
works with the last chained DMA descriptor).
Before I write my own MAC driver, I wanted to get a benchmark running
with the original code to compare it to LPCs Iperf benchmarks. They
implemented a zero-copy MAC driver for LwIP that achieves almost line
speed (at much slower clock rates than ST).
For my device: Ping round trip time is between 130us and 250us (1 Switch
between Linux+STM32F407 running at 150MHz), but >0% packet loss, TCP is
unreliable and UDP seems to work, but not benchmarked yet.
So: Any open (BSD/GPL), stable and optimally zero-copy MAC drivers for
STM32F4x7+FreeRTOS available here? Maybe I can get some inspiration from
ChibiOS's driver as they seem to have mostly not used ST code.
Regards
Claudius
On 6/23/2013 7:16 AM, ella wrote:
The problem is not FreeRTOS but buggy and ugly STM32 netif driver. I have
studied original driver provided by ST and had nothing but rewrite it.
Just one example of wrong architecture of this driver. This is from
low_level_output():
buffer = (u8 *)(DMATxDescToSet->Buffer1Addr);
for(q = p; q != NULL; q = q->next)
{
memcpy((u8_t*)&buffer[l], q->payload, q->len);
l = l + q->len;
}
Consider that buffers are allocated as
extern uint8_t Tx_Buff[ETH_TXBUFNB][ETH_TX_BUF_SIZE];
and are linked to chained DMA descriptors.
If packet size bigger then ETH_TX_BUF_SIZE you are at potential danger of
wrap around that is not treated in code. Same happens for RX flow. So no
surprise you have a problems with big packets.
And this is only one place, there is a number of others. There are also a
few races.
In short DO NOT USE THIS DRIVER.
--
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