2002-01-19 15:11:14

by Lukas Geyer

Subject: 2.4.18pre4 on PPC, Byteswap in dmasound_awacs.c

I have an ibook2 and the Keylargo controller of this laptop seems not to
be able to do hardware byteswap. However, the driver set hw_can_byteswap
to 1 due to the following in drivers/sound/dmasound/dmasound_awacs.h:

+ struct device_node *mio ;
+ unsigned int *p, rev = 0 ;
+
+ /* if seems that Keylargo (at least rev2) can't byte-swap */
+
+ for (mio = io->parent; mio ; mio = mio->parent) {
+ if (strcmp(mio->name, "mac-io") == 0) {
+ if (device_is_compatible(mio, "Keylargo")){
+ p = (unsigned int *)
+ get_property(mio, "revision-id", 0);
+ if (p)
+ rev = *p ;
+ }
+ break;
+ }
+ }
+ if (rev >= 2) {
+ hw_can_byteswap = 0;

My Keylargo controller reports 0 as the revision number, thus it might
either be advisable to put that hw_can_byteswap = 0 into the innermost
block and not check the revision at all (if no Keylargo can do byteswap)
or or to put a check for revision <= 2 (after all, isn't it logical to
assume that only later revisions will be able to do byteswap?) inside the
innermost block and set hw_can_byteswap to 0 there.

Lukas

2002-01-19 16:19:06

by Benjamin Herrenschmidt

Subject: Re: 2.4.18pre4 on PPC, Byteswap in dmasound_awacs.c

>My Keylargo controller reports 0 as the revision number, thus it might
>either be advisable to put that hw_can_byteswap = 0 into the innermost
>block and not check the revision at all (if no Keylargo can do byteswap)
>or or to put a check for revision <= 2 (after all, isn't it logical to
>assume that only later revisions will be able to do byteswap?) inside the
>innermost block and set hw_can_byteswap to 0 there.

You are right, this is a pangea chipset (KeyLargo & UniNorth in a
single ASIC) and in that case, KL provides no rev. number. I'll fix
this.

Thanks for the report,
Ben.