Averatec 6240 pcmcia_socket0: unable to apply power

[Daniel Ritz]

On Thursday 08 September 2005 22.33, Linus Torvalds wrote:
> 
> On Thu, 8 Sep 2005, Daniel Ritz wrote:
> >
> > something like the attached patch...
> > 
> > cc:ing linus as he is the one that added the "find the largest gap" code
> > that comes handy here...
> 
> You've got typos there ("rounded up to a multiple of 6 MB" - it should be

whoops! you just convinced me to hide that old keyboard somewhere and
use a sane one :)

> 64). Also, I really think you'd be much better off keeping the old gap 
> code, and rounding _later_.
> 
> The "round later" approach allows you to look at the size of the gap, and
> use that to decide whether to round or not. That's what the question in
> the comment is talking about, how we "now have the technology" for it.
> 
> Also, while it's wonderful to round up in general, there really would be
> an advantage to have a gap _offset_ too: it's safer than rounding up to a
> big area, if only because it might help against people doing prefetches
> etc offset off the last few pages of RAM and into a PCI mapping..
> 
> So I'd really prefer to see the gap-finding remain the same, and 
> then have just the pci_mem_start calculations be something like
> 
> 	/*
> 	 * See how much we want to round up: start off with
> 	 * rounding to the next 1MB area.
> 	 */
> 	round = 0x100000;
> 	while ((gapsize >> 4) > round)
> 		round += round;
> 	/* Fun with two's complement */
> 	pci_mem_start = (gapstart + round) & -round;
> 
> which will not really "round up" but actually "gap up" (ie it's guaranteed
> to leave a gap) to the next power-of-two, where we select the rounding 
> size depending on how much space we have in the gap.
> 
> The above should result in a "rounding gap" of 64MB if the real gap is 
> 1GB..
> 

i did the math for this months pcmcia breakages because of that...and yes,
works just fine. so attached your thinggy in diff -u format.

> The other alternative is to make PCI allocations generally start at the
> high range of the allowable - judging by the lspci listings I've seem from
> people under Windows, that seems to be what Windows does, which might be a

looking at my other box, yes. all pci devices are above 3GB at least.

> good idea (ie the closer we match windows allocation patterns, the more
> likely we're to not hit some unmarked region - because windows testing
> would have hit it too).

yeah.

> Hmm?
> 
> 		Linus

rgds
-daniel

----

diff --git a/arch/i386/kernel/setup.c b/arch/i386/kernel/setup.c
--- a/arch/i386/kernel/setup.c
+++ b/arch/i386/kernel/setup.c
@@ -1299,7 +1299,7 @@ legacy_init_iomem_resources(struct resou
  */
 static void __init register_memory(void)
 {
-	unsigned long gapstart, gapsize;
+	unsigned long gapstart, gapsize, round;
 	unsigned long long last;
 	int	      i;
 
@@ -1344,14 +1344,14 @@ static void __init register_memory(void)
 	}
 
 	/*
-	 * Start allocating dynamic PCI memory a bit into the gap,
-	 * aligned up to the nearest megabyte.
-	 *
-	 * Question: should we try to pad it up a bit (do something
-	 * like " + (gapsize >> 3)" in there too?). We now have the
-	 * technology.
+	 * See how much we want to round up: start off with
+	 * rounding to the next 1MB area.
 	 */
-	pci_mem_start = (gapstart + 0xfffff) & ~0xfffff;
+	round = 0x100000;
+	while ((gapsize >> 4) > round)
+		round += round;
+	/* Fun with two's complement */
+	pci_mem_start = (gapstart + round) & -round;
 
 	printk("Allocating PCI resources starting at %08lx (gap: %08lx:%08lx)\n",
 		pci_mem_start, gapstart, gapsize);
diff --git a/arch/x86_64/kernel/e820.c b/arch/x86_64/kernel/e820.c
--- a/arch/x86_64/kernel/e820.c
+++ b/arch/x86_64/kernel/e820.c
@@ -567,7 +567,7 @@ unsigned long pci_mem_start = 0xaeedbabe
  */
 __init void e820_setup_gap(void)
 {
-	unsigned long gapstart, gapsize;
+	unsigned long gapstart, gapsize, round;
 	unsigned long last;
 	int i;
 	int found = 0;
@@ -604,14 +604,14 @@ __init void e820_setup_gap(void)
 	}
 
 	/*
-	 * Start allocating dynamic PCI memory a bit into the gap,
-	 * aligned up to the nearest megabyte.
-	 *
-	 * Question: should we try to pad it up a bit (do something
-	 * like " + (gapsize >> 3)" in there too?). We now have the
-	 * technology.
+	 * See how much we want to round up: start off with
+	 * rounding to the next 1MB area.
 	 */
-	pci_mem_start = (gapstart + 0xfffff) & ~0xfffff;
+	round = 0x100000;
+	while ((gapsize >> 4) > round)
+		round += round;
+	/* Fun with two's complement */
+	pci_mem_start = (gapstart + round) & -round;
 
 	printk(KERN_INFO "Allocating PCI resources starting at %lx (gap: %lx:%lx)\n",
 		pci_mem_start, gapstart, gapsize);