Hi Till,
Thank you for taking the time to look over the BSP :)
You pointed out two important problems of the driver.
The first has already been fixed a few days ago on my github repository,
I will try to merge it ASAP with RTEMS CVS, I opened a PR about that [0].
For the "allocation of the dma buffer on the stack" bug, I haven't seen
it :) Thanks for spotting that ! *ashamed*
I just pushed a fixed on my github for that : [1]
This driver is indeed not production ready, there is still a lot of
cleaning (and implementing) to do. I have only a little time to give to
this task so it will be done but when ? I don't know.
Feel free to merge these commits with the CVS, but it will not be a
straight forward merge since my github repository has a lot of commit
that your CVS doesn't have. We are out of sync.
But for such small commits it should be quite easy !
Thank you again for your comments :)
[0] - https://www.rtems.org/bugzilla/show_bug.cgi?id=1739
[1] -
https://github.com/fallen/rtems-milkymist/commit/459b785b7f26d0eac52f6fb3efc0c9432d56bd69
Regards,
Yann Sionneau
Le 24/02/11 00:18, Till Straumann a écrit :
Today I started playing with the milkymist BSP in HEAD.
After some hacking I got some life out of lm32-qemu and this
BSP but I'm not sure it has reached production quality quite yet.
When sending a packet, minimac_sendpacket() copies the
entire mbuf chain holding the packet into a driver-buffer
(struct mm_packet) which is much smaller than the interface
MTU and which is allocated *on*the*stack* and then handed
(by reference) to the chip (for DMA, I guess).
Any packet that is larger than 128 bytes overruns the stack
and since it is very likely that the packet buffer is popped
before the hardware is done reading it from memory it may
very well be corrupted.
Other peculiarities include not declaring memory-mapped
registers as 'volatile' (in the network- and other drivers).
-- T.
PS: Here's a snippet of that code
static void minimac_sendpacket(struct ifnet *ifp, struct mbuf *m)
{
struct mbuf *nm = m;
struct minimac_softc *sc = &minimac_softc;
unsigned int len = 0;
struct mm_packet p;
unsigned int crc;
uint8_t i;
for (i = 0 ; i < 7 ; i++) // Preamble
p.preamble[i] = 0x55;
p.preamble[7] = 0xd5;
do
{
unsigned int mlen;
mlen = nm->m_len;
if (nm->m_len > 0) {
m_copydata(nm, 0, mlen, p.raw_data + len);
len += nm->m_len;
} while ( (nm = nm->m_next) != 0 );
for ( ; len < 60 ; len++)
p.raw_data[len] = 0x00; // Padding
crc = mm_ether_crc32((uint8_t *)p.raw_data, len); // CRC32
p.raw_data[len] = crc & 0xff;
p.raw_data[len+1] = (crc & 0xff00) >> 8;
p.raw_data[len+2] = (crc & 0xff0000) >> 16;
p.raw_data[len+3] = crc >> 24;
len += 4; // We add 4 bytes of CRC32
if (len + 8 < 64) {
printk("[minimac] Packet is too small !\n");
sc->txErrors++; // update stats
return;
}
minimac_write(MM_MINIMAC_TXADR, (unsigned int)&p);
minimac_write(MM_MINIMAC_TXREMAINING, (unsigned int)(len + 8));
}
where struct mm_packet is
struct mm_packet {
unsigned char preamble[8];
char raw_data[MLEN]; /* MLEN == 128 bytes! */
} __attribute__((aligned(4), packed));
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