[Expired for QEMU because there has been no activity for 60 days.]
** Changed in: qemu
Status: Incomplete => Expired
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https://bugs.launchpad.net/bugs/1306818
Title:
resetting moder register in opencores_eth.c code (ethernet IP core
specification code)
Status in QEMU:
Expired
Bug description:
Hi, I would like to report a possible error in the code
qemu/hw/net/opencores_eth.c
The corresponding data sheet :
http://www.cprover.org/firmware/doc/ethoc/eth_speci.pdf
In the code, there is a function open_eth_moder_host_write.
static void open_eth_moder_host_write(OpenEthState *s, uint32_t val)
{
uint32_t set = val & ~s->regs[MODER];
if (set & MODER_RST) {
open_eth_reset(s);
}
s->regs[MODER] = val;
if (set & MODER_RXEN) {
s->rx_desc = s->regs[TX_BD_NUM];
open_eth_notify_can_receive(s);
}
if (set & MODER_TXEN) {
s->tx_desc = 0;
open_eth_check_start_xmit(s);
}
}
This piece of code is executed when MODER (Mode Register) resister is
command to updated to ‘val’.
In case of reset, as you can see, if the MODER_RST bit (0x800) bit is set &&
the old MODER_RST bit (0x800) of MODER register is clear, the code falls into
the if(set & MODER_RST) branch. Then, it calls open_eth_reset(s), which does
“s->regs[MODER] = 0xa000;”. Now, the MODER register is reset to 0xa000. Page 9
of the data sheet (http://www.cprover.org/firmware/doc/ethoc/eth_speci.pdf)
specifies the reset value of the moder is 0000A000h. So far, the code works
fine.
Then, the open_eth_moder_host_write function does not end but executes but
executes “s->regs[MODER] = val;” line. Now, the MODER register is not 0xa000
any more.
In fact, since the MODER_RST bit of ‘val’ is 1, now the MODER_RST bit of the
MODER register becomes 1 as well. Suppose one somehow calls this
open_eth_moder_host_write again with val = MODER_RST with purpose of resetting
again. Since the MODER_RST bit is 1, (set = val & ~s->regs[MODER]) & MODER_RST
is zero. So after this, resetting again is not possible.
Hence, I doubt the function’s correctness here. I think it could be
better if the function changes to :
if (set & MODER_RST) {
open_eth_reset(s);
return;
}
Please let me know if I am correct.
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