Manfred Spraul wrote:
Jeff wrote:
* Interrupt handler is SCARY. You can potentially take and release
the spinlock -many times- during a single interrupt.
I think that can happen only in theory: A new packet is completed while
the driver processes rx packets. I all normal cases there should be one
spinlock operation per tx irq, and 0 per rx irq.
And error handling IMHO doesn't count: it should be rare.
Or do I overlook a common case?
Any amount of load at all will lead to multiple interations of the
master loop in the interrupt handler.
+#define NV_MIIPHY_DELAY 10
+#define NV_MIIPHY_DELAYMAX 10000
Style: it's fairly silly to mix enums and constants.
Right now: enum for the nic registers, #define for the rest. If you
don't like it I can change it.
enums are definitely preferred... communicates more type/symbol
information to the compiler and more symbol info to the debugger.
+/* General driver defaults */
+#define NV_WATCHDOG_TIMEO (2*HZ)
this seems too short, and might trigger on normal events?
I think I copied it from another driver - which value would you recommend?
5 seconds is the norm, but it also depends on whether your link
interrupt is 100% reliable. If you don't have to synchronize the link
watchdog timeout with other driver-private timers, the task is easier.
Tangent -- you may wish to check for link in ->tx_timeout(), before
resetting the NIC. Again, this depends on link interrupt/timer setup as
well. The basic point is that TX timeout -may- occur because link went
away. One way to handle this is to ensure that link-down events are
always noticed before the watchdog timer kicks. Another way to handle
this is to simply check for link when ->tx_timeout() is called.
+static inline struct fe_priv *get_nvpriv(struct net_device *dev)
+{
+ return (struct fe_priv *) dev->priv;
+}
What's the point of this wrapper?
You don't need to cast from a void pointer, either.
I usually try to write code that compiles as cpp - is that a forbidden
in kernel modules?
It's pointless in C, and so I've been stripping such casts out of all
net drivers when I find them.
+/*
+ * alloc_rx: fill rx ring entries.
+ * Return 1 if the allocations for the skbs failed and the
+ * rx engine is without Available descriptors
+ */
+static int alloc_rx(struct net_device *dev)
+{
[snip]
+ return 0;
+}
skb_reserve() seems to be missing
Do you have specs that show that all nForce versions support unaligned
buffers? skb_reserve is a performance feature, I don't want to add it
yet. Testing that it works is on our TODO list.
hmmmm, is nForce ever found on non-x86 boxes? I would think that
skb_reserve might be -required- for some platforms.
I wonder about calling dev_kfree_skb() from dev->tx_timeout() with
dev->xmit_lock held...
Is that bug in the networking core still not fixed?
I am not aware of a bug in this area.
+ /* 2) check that the packets were not sent already: */
+ tx_done(dev);
bug: tx_done unconditionally calls dev_kfree_skb_irq(), but here we
are not in an interrupt.
What is the xxx_kfree_skb_xxx function that just works?
dev_kfree_skb_any
+ /*
+ * the packet is for us - immediately tear down the pci
mapping, and
+ * prefetch the first cacheline of the packet.
+ */
+ pci_unmap_single(np->pci_dev, np->rx_dma[i],
+ np->rx_skbuff[i]->len,
+ PCI_DMA_FROMDEVICE);
+ prefetch(np->rx_skbuff[i]->data);
is this just guessing? or has this actually shown some value?
I would prefer not to put stuff like this in unless it shows a
measureable CPU usage or cache miss impact.
Just guessing - it shouldn't hurt. CPU usage won't be important until
nForce supports GigE. Should I remove it for now?
I would rather remove it. "premature optimization" and all that.
Otherwise this guess will be cut-n-pasted into other drivers, I
guarantee, all without any verification of the guess... :)
+/*
+ * change_mtu: dev->change_mtu function
+ * Called with dev_base_lock held for read.
+ */
+static int change_mtu(struct net_device *dev, int new_mtu)
+{
+ if (new_mtu > DEFAULT_MTU)
+ return -EINVAL;
+ dev->mtu = new_mtu;
+ return 0;
+}
bug #1: have you tested changing the MTU while the NIC is actually
running?
What should the nic do? I'll continue to allocate 1.8 kB buffers because
I don't know how to reconfigure the nic hardware to reject large packets.
Fair enough. You may wish to (after testing!) increase DEFAULT_MTU by 4
bytes, to support VLAN.
bug #2: need a minimum bound for the MTU as well
What is the minimum MTU? I remember a flamewar lkml about 200 byte MTU
for noisy radio links.
Usually the ethernet standard 60 is fine.
+ for (i=0; ; i++) {
+ events = readl(base + NvRegIrqStatus) & NVREG_IRQSTAT_MASK;
+ writel(NVREG_IRQSTAT_MASK, base + NvRegIrqStatus);
+ pci_push(base);
+ dprintk(KERN_DEBUG "%s: irq: %08x\n", dev->name, events);
+ if (!(events & np->irqmask))
+ break;
bug: check for 0xffffffff
What causes 0xfffffff? Hotplug? I think the irq handler could leave
immediately if a reserved bit is set. I'll add that.
Yes, hot unplug or hardware fault.
+ if (i == 32) {
+ printk(KERN_INFO "%s: open: failing due to lack of suitable
PHY.\n",
+ dev->name);
+ ret = -EINVAL;
+ goto out_drain;
+ }
bug: check #0 after checking #1, before giving up
MII id 0 a valid mii address? Or is that broadcast to all?
It's usually something akin to an alias of one of the other phy id's,
but if you found -no- phys at all, it wouldn't hurt to try zero.
Thanks,
Jeff
|