On 09/08/2014 05:36 AM, Linus Walleij wrote: > On Mon, Sep 8, 2014 at 2:20 PM, Arnd Bergmann <arnd@xxxxxxxx> wrote: >> On Monday 08 September 2014 13:38:04 Linus Walleij wrote: >>> + of_property_read_u32(np, "cache-size", &size); >>> + of_property_read_u32(np, "cache-sets", &sets); >>> + >>> + if (!size || !sets) >>> + return; >>> + >>> + way_size = size / sets; >> >> Going back to this one: Isn't (size / sets) the set-size rather >> than the way-size? >> >> After we discussed this on IRC, I had expected a calculation like >> >> set_size = size / sets; >> ways = set_size / line_size; >> way_size = size / ways; > > First: in this PB1176 case: > > set_size = 128K/8 = 16K > ways = 16K/32 = 512 bytes > way_size = 128K/512 = 128 bytes > > Well maybe it's the ARM reference manual internal lingo that > is actually causing the confusion here. It will say something > like: > > [19:17] Way-size 3’b000 = Reserved, internally mapped to 16KB > 3’b001 = 16KB, this is the default value > 3’b010 = 32KB > 3’b011 = 64KB > 3’b100 = 128KB > 3’b101 = 256KB > 3’b110 to 3’b111 = Reserved, internally mapped to 256 KB > > OK way-size ... is in the 16 thru 256KB range, which fits nicely > with set size incidentally. And also corresponds to current > comments in the code such as this from > arch/arm/mach-realview/realview_pb1176.c: > > #ifdef CONFIG_CACHE_L2X0 > /* > * The PL220 needs to be manually configured as the hardware > * doesn't report the correct sizes. > * 128kB (16kB/way), 8-way associativity, event monitor and > * parity enabled, ignore share bit, no force write allocate > * Bits: .... ...0 0111 0011 0000 .... .... .... > */ > l2x0_init(__io_address(REALVIEW_PB1176_L220_BASE), 0x00730000, > 0xfe000fff); > #endif > > I can add a comment explaining that ARMs terminology does > not match the academic terminology or something, and say that > the thing we poke into "way-size" is actually "set size", if we agree > that is what we're seeing here. > > Florian: what was your interpretation? Yes that was my interpretation as well, that we could have 'way-size' and 'set-size' be the same things here, now that I re-think about it, I am not sure anymore. More to follow on Arnd's reply to this email. -- Florian -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
