e1000e driver

[macpacheco]

The first driver I converted to C.
It seems like the current assembly code only receives the first packet.
Here's how I solved on the C side:

// Constants
#define i8257x_MAX_PKT_SIZE	16384
#define i8257x_MAX_DESC		32		// Must be 16, 32, 64, 128, etc.
// Variables
u64 os_tx_desc[i8257x_MAX_DESC<<1] __attribute__((aligned(128))),
    os_rx_desc[i8257x_MAX_DESC<<1] __attribute__((aligned(128)));
u8 os_PacketBuffers[16384];
u32 i8257x_tx_lasttail = 0, i8257x_rx_lasthead1 = 0, i8257x_rx_lasthead = 0;

On reset if I set RDT to the full MAX_DESC it fails to receive any packets, but -1 works.
    i8257x_REG(i8257x_RDLEN) = sizeof(os_rx_desc); // Receive Descriptor Length
    i8257x_REG(i8257x_RDH)   = 0;                   // Receive Descriptor Head
    i8257x_REG(i8257x_RDT)   = i8257x_rx_lasthead1 = i8257x_MAX_DESC-1;   // Receive Descriptor Tail

    i8257x_REG(i8257x_TDLEN) = sizeof(os_tx_desc);  // Receive Descriptor Length
    i8257x_REG(i8257x_TDH)   = 0;                   // Receive Descriptor Head
    i8257x_REG(i8257x_TDT)   = i8257x_MAX_DESC;     // Receive Descriptor Tail
    // Transmit Control Register
    i8257x_REG(i8257x_TCTL)  = 1 << i8257x_TCTL_EN | 1 << i8257x_TCTL_PSP | 1 << i8257x_TCTL_CT | 1 << i8257x_TCTL_COLD;
    i8257x_REG(i8257x_CTRL_EXT) |= 1 << i8257x_CTRL_EXT_DRV_LOAD;

don't want to function in promisc mode, and don't want to process jumbo packets, so two bits were removed from TCTL.

u32 net_i8257x_poll(u64 *packet)
{   register volatile u8 *i8257x_REGs = os_NetIOMem.bar_io;
    u32 length;
    volatile u64 *p_rx_desc = &os_rx_desc[i8257x_rx_lasthead<<1];
    if ( (length = *++p_rx_desc) == 0) return 0;
    *p_rx_desc = 0;
    // Wrap around when lasthead gets to the maximum descriptors we set
    if ((++i8257x_rx_lasthead) == i8257x_MAX_DESC-1) i8257x_rx_lasthead=0;
    // Allow NIC to reuse the initial buffers when we reach 1/2 of the ring
    if (++i8257x_rx_lasthead1 > i8257x_MAX_DESC/2)
    {   i8257x_REG(i8257x_RDH)=0;
        i8257x_rx_lasthead1=i8257x_REG(i8257x_RDH);
    }
    return length;
}

Removed the +1 AND logic replaced with an equality comparison.
The lasthead1 variable is used to reset RDH less often back to zero once we rx half as many DESC as fits.
Similar poll without lasthead1, untested.

; -----------------------------------------------------------------------------
; net_i8257x_poll - Polls the Intel 8257x NIC for a received packet
;  IN:	RDI = Location to store packet
; OUT:	RCX = Length of packet
; Note:	RDESC Descriptor Format:
;	First Qword:
;	Bits 63:0 - Buffer Address
;	Second Qword:
;	Bits 15:0 - Length
;	Bits 31:16 - Fragment Checksum
;	Bits 39:32 - STA - Status
;	Bits 47:40 - Errors
;	Bits 63:48 - VLAN
net_i8257x_poll:
	push rdi
	push rsi			; Used for the base MMIO of the NIC
	push rax

	mov rdi, os_rx_desc
	mov rsi, [os_NetIOBaseMem]	; Load the base MMIO of the NIC

	; Calculate the descriptor to read from
	mov eax, [i8257x_rx_lasthead]
	shl eax, 4			; Quick multiply by 16
	add eax, 8			; Offset to bytes received
	add rdi, rax			; Add offset to RDI
	; Todo: read all 64 bits. check status bit for DD
	xor ecx, ecx			; Clear RCX
	mov cx, [rdi]			; Get the packet length
	cmp cx, 0
	je net_i8257x_poll_end		; No data? Bail out

	xor eax, eax
	stosq				; Clear the descriptor length and status

	; Increment i8257x_rx_lasthead with wraparound
	mov eax, [i8257x_rx_lasthead]
	inc eax
	cmp eax, i8257x_MAX_DESC - 1
	jne net_i8257x_nowrap
	xor eax, eax
net_i8257x_nowrap:
	mov [i8257x_rx_lasthead], eax

	; Minimize acesses to registers, wrap it back to zero once it reaches half way
	cmp eax, i8257x_MAX_DESC/2
	jne net_i8257x_nowrap2
	mov dword [rsi+i8257x_RDT], 0
net_i8257x_nowrap2:
	pop rax
	pop rsi
	pop rdi
	ret

net_i8257x_poll_end:
	xor ecx, ecx
	pop rax
	pop rsi
	pop rdi
	ret
; -----------------------------------------------------------------------------

How to easily flood BM with packets to test drivers:

• Use -netdev tap
• bash (root):

ip link set dev tap0 up # Bring tap0 up
ip a add dev tap0 192.168.1.1/24 # Give it a source ip
 # Give BM a static arp so IP packets go through even without ARP response from BM
ip neigh replace dev tap0 lladdr 10:11:12:08:25:74 192.168.1.2 # Need to match BM eth MAC
ping -f -l 10 192.168.1.2 # Flood ping with 10 preload
With this I was able to send thousands of packets to BM C without crashes or freezes.

[macpacheco]

drivers/net/i8257x.asm:

        xor eax, eax
        mov [rsi+i8257x_RDH], eax       ; Receive Descriptor Head
        mov eax, i8257x_MAX_DESC - 1
        mov [rsi+i8257x_RDT], eax       ; Receive Descriptor Tail
        mov eax, 1 << i8257x_RCTL_EN | 1 << i8257x_RCTL_UPE | 1 << i8257x_RCTL_MPE | 1 << i8257x_RCTL_LPE | 1 << i8257x_RCTL_BAM | 1 << i8257x_RCTL_SECRC

You need to set RDT to number of descriptors - 1 to use all of them.
Then you're original reception code can be used correctly.
Updated poll code:

        xor eax, eax
        stosq                           ; Clear the descriptor length and status

        mov eax, [i8257x_rx_lasthead]
        ; Minimize acesses to registers, update RDT each time 1/4 of MAX_DESC have been received
        mov rdi, rax
        and rdi, i8257x_MAX_DESC >> 4 - 1 ; Zero higher bits
        cmp rdi, 0 
        jne net_i8257x_nowrap
        ; Save descriptor number before update to Rx Tail
        mov dword [rsi+i8257x_RDT], rax

        ; Increment i8257x_rx_lasthead with wraparound
        inc eax
        and eax, i8257x_MAX_DESC - 1
        mov [i8257x_rx_lasthead], eax
net_i8257x_nowrap:
        pop rax
        pop rsi
        pop rdi
        ret

net_i8257x_poll_end:
        xor ecx, ecx
        pop rax
        pop rsi
        pop rdi
        ret

I wrote a shoehorned ARP and ICMP reply logic on a i8257x interrupt. I'm able to send pings as fast as linux can generate them, without a single loss BM2 C side.

[IanSeyler]

Awesome! Can you tell me more about the receive issue you mentioned where it only saw one packet? I tested this driver in QEMU and with a physical card as well.