Re: pismo upgraded to 750fx not detected correctly

On Sun, 22 Jun 2003, Benjamin Herrenschmidt wrote:

quoted

Note that the kernel doesn't use the device tree to detect the
CPU type. It rather runs the PVR through a table in
arch/ppc/kernel/cputable.c. There is currently no hook you could
use to 'fix' that. Ideally, you should make sure the CPU is properly
detected before the fixups are done or you may "lose" some 750fx
specific code.

Ok, so to properly detect the cpu, I ported Terry's code to assembler and
added it to identify_cpu in arch/ppc/kernel/misc.S.  See the attached diff
below.  This code does the following:

- detects 750FX strapped as 750 in identify_cpu
- stores the real pvr is a new global called 'real_pvr'
- updates the cache and clock_frequency values in the device tree at the
  end of finish_device_tree() in prom.c
- makes use of real_pvr instead of mfspr(PVR) in show_cpuinfo() in setup.c

Note that I currently hardcode the clock frequency to 900MHz (speed of my
pismo).  I'll fix that as soon as I learn how to detect the true processor
speed.

For a complete solution, I believe all that needs to be done is to change
all instances of 'mfspr(PVR)' to 'real_pvr', except the one in prom.c.

Also, I just learned ppc assembler today while doing this so please let me
know if you see a more efficient/eloquent way to do the cpu detection, or
if you find a bug in what I have.  I've only tested this on my upgraded
pismo and it seems to work.  Here's my /proc/cpuinfo now:

  cpu             : 750FX
  temperature     : 18-20 C (uncalibrated)
  clock           : 900MHz
  revision        : 2.2 (pvr 7000 0202)
  bogomips        : 1795.68
  machine         : PowerBook3,1
  motherboard     : PowerBook3,1 MacRISC2 MacRISC Power Macintosh
  detected as     : 70 (PowerBook Pismo)
  pmac flags      : 0000000f
  L2 cache        : 512K unified
  memory          : 256MB
  pmac-generation : NewWorld

Chris.


diff -c -r linux-2.4.21-ac1.orig/arch/ppc/kernel/cputable.c linux-2.4.21-ac1/arch/ppc/kernel/cputable.c
*** linux-2.4.21-ac1.orig/arch/ppc/kernel/cputable.c	Fri Jun 13 10:51:31 2003

--- linux-2.4.21-ac1/arch/ppc/kernel/cputable.c	Sun Jun 22 21:10:37 2003

***************
*** 18,23 ****

--- 18,25 ----

  struct cpu_spec* cur_cpu_spec[NR_CPUS];

+ unsigned int real_pvr;
+
  extern void __setup_cpu_601(unsigned long offset, int cpu_nr, struct cpu_spec* spec);
  extern void __setup_cpu_603(unsigned long offset, int cpu_nr, struct cpu_spec* spec);
  extern void __setup_cpu_604(unsigned long offset, int cpu_nr, struct cpu_spec* spec);

diff -c -r linux-2.4.21-ac1.orig/arch/ppc/kernel/misc.S linux-2.4.21-ac1/arch/ppc/kernel/misc.S
*** linux-2.4.21-ac1.orig/arch/ppc/kernel/misc.S	Fri Jun 13 10:51:31 2003

--- linux-2.4.21-ac1/arch/ppc/kernel/misc.S	Sun Jun 22 21:25:32 2003

***************
*** 113,118 ****

--- 113,139 ----
  	addis	r8,r3,cpu_specs@ha
  	addi	r8,r8,cpu_specs@l
  	mfpvr	r7
+
+ /* check for 750fx strapped on as 750 */
+ 	srwi	r6,r7,16
+ 	cmpli	0,r6,8
+ 	bne	1f
+ 	mfspr	r5,0x3F1
+ 	srwi.	r6,r5,17
+ 	bso	2f

+ 	xori	r6,r5,0x0200
+ 	b	3f
+ 2:
+ 	xori	r6,r5,0x0002
+ 3:
+ 	mtspr	0x3F1,r6
+ 	mfspr	r6,0x3F1
+ 	cmplw	0,r5,r6
+ 	beq	1f
+
+ /* pvr is actually 0x7000nnnn, not 0x0008nnnn */
+ 	xoris	r7,r7,0x7008
+
  1:
  	lwz	r5,CPU_SPEC_PVR_MASK(r8)
  	and	r5,r5,r7
***************
*** 127,132 ****

--- 148,158 ----
  	slwi	r4,r4,2
  	sub	r8,r8,r3
  	stwx	r8,r4,r6
+
+ 	addis	r6,r3,real_pvr@ha
+ 	addi	r6,r6,real_pvr@l
+ 	stwx	r7,0,r6