• Andreas Herrmann's avatar
    [CPUFREQ] powernow-k8: ignore out-of-range PstateStatus value · a266d9f1
    Andreas Herrmann authored
    A workaround for AMD CPU family 11h erratum 311 might cause that the
    P-state Status Register shows a "current P-state" which is larger than
    the "current P-state limit" in P-state Current Limit Register. For the
    wrong P-state value there is no ACPI _PSS object defined and
    powernow-k8/cpufreq can't determine the proper CPU frequency for that
    state.
    
    As a consequence this can cause a panic during boot (potentially with
    all recent kernel versions -- at least I have reproduced it with
    various 2.6.27 kernels and with the current .28 series), as an
    example:
    
    powernow-k8: Found 1 AMD Turion(tm)X2 Ultra DualCore Mobile ZM-82 processors (2 \
    )
    powernow-k8:    0 : pstate 0 (2200 MHz)
    powernow-k8:    1 : pstate 1 (1100 MHz)
    powernow-k8:    2 : pstate 2 (600 MHz)
    BUG: unable to handle kernel paging request at ffff88086e7528b8
    IP: [<ffffffff80486361>] cpufreq_stats_update+0x4a/0x5f
    PGD 202063 PUD 0
    Oops: 0002 [#1] SMP
    last sysfs file:
    CPU 1
    Modules linked in:
    Pid: 1, comm: swapper Not tainted 2.6.28-rc3-dirty #16
    RIP: 0010:[<ffffffff80486361>]  [<ffffffff80486361>] cpufreq_stats_update+0x4a/0\
    f
    Synaptics claims to have extended capabilities, but I'm not able to read them.<6\
    6
    RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffff88006e7528c0
    RDX: 00000000ffffffff RSI: ffff88006e54af00 RDI: ffffffff808f056c
    RBP: 00000000fffee697 R08: 0000000000000003 R09: ffff88006e73f080
    R10: 0000000000000001 R11: 00000000002191c0 R12: ffff88006fb83c10
    R13: 00000000ffffffff R14: 0000000000000001 R15: 0000000000000000
    FS:  0000000000000000(0000) GS:ffff88006fb50740(0000) knlGS:0000000000000000
    Unable to initialize Synaptics hardware.
    CS:  0010 DS: 0018 ES: 0018 CR0: 000000008005003b
    CR2: ffff88086e7528b8 CR3: 0000000000201000 CR4: 00000000000006e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
    Process swapper (pid: 1, threadinfo ffff88006fb82000, task ffff88006fb816d0)
    Stack:
     ffff88006e74da50 0000000000000000 ffff88006e54af00 ffffffff804863c7
     ffff88006e74da50 0000000000000000 00000000ffffffff 0000000000000000
     ffff88006fb83c10 ffffffff8024b46c ffffffff808f0560 ffff88006fb83c10
    Call Trace:
     [<ffffffff804863c7>] ? cpufreq_stat_notifier_trans+0x51/0x83
     [<ffffffff8024b46c>] ? notifier_call_chain+0x29/0x4c
     [<ffffffff8024b561>] ? __srcu_notifier_call_chain+0x46/0x61
     [<ffffffff8048496d>] ? cpufreq_notify_transition+0x93/0xa9
     [<ffffffff8021ab8d>] ? powernowk8_target+0x1e8/0x5f3
     [<ffffffff80486687>] ? cpufreq_governor_performance+0x1b/0x20
     [<ffffffff80484886>] ? __cpufreq_governor+0x71/0xa8
     [<ffffffff80484b21>] ? __cpufreq_set_policy+0x101/0x13e
     [<ffffffff80485bcd>] ? cpufreq_add_dev+0x3f0/0x4cd
     [<ffffffff8048577a>] ? handle_update+0x0/0x8
     [<ffffffff803c2062>] ? sysdev_driver_register+0xb6/0x10d
     [<ffffffff8056592c>] ? powernowk8_init+0x0/0x7e
     [<ffffffff8048604c>] ? cpufreq_register_driver+0x8f/0x140
     [<ffffffff80209056>] ? _stext+0x56/0x14f
     [<ffffffff802c2234>] ? proc_register+0x122/0x17d
     [<ffffffff802c23a0>] ? create_proc_entry+0x73/0x8a
     [<ffffffff8025c259>] ? register_irq_proc+0x92/0xaa
     [<ffffffff8025c2c8>] ? init_irq_proc+0x57/0x69
     [<ffffffff807fc85f>] ? kernel_init+0x116/0x169
     [<ffffffff8020cc79>] ? child_rip+0xa/0x11
     [<ffffffff807fc749>] ? kernel_init+0x0/0x169
     [<ffffffff8020cc6f>] ? child_rip+0x0/0x11
    Code: 05 c5 83 36 00 48 c7 c2 48 5d 86 80 48 8b 04 d8 48 8b 40 08 48 8b 34 02 48\
    
    RIP  [<ffffffff80486361>] cpufreq_stats_update+0x4a/0x5f
     RSP <ffff88006fb83b20>
    CR2: ffff88086e7528b8
    ---[ end trace 0678bac75e67a2f7 ]---
    Kernel panic - not syncing: Attempted to kill init!
    
    In short, aftereffect of the wrong P-state is that
    cpufreq_stats_update() uses "-1" as index for some array in
    
    cpufreq_stats_update (unsigned int cpu)
    {
    ...
         if (stat->time_in_state)
                    stat->time_in_state[stat->last_index] =
                            cputime64_add(stat->time_in_state[stat->last_index],
                                          cputime_sub(cur_time, stat->last_time));
    ...
    }
    
    Fortunately, the wrong P-state value is returned only if the core is
    in P-state 0. This fix solves the problem by detecting the
    out-of-range P-state, ignoring it, and using "0" instead.
    
    Cc: Mark Langsdorf <mark.langsdorf@amd.com>
    Signed-off-by: default avatarAndreas Herrmann <andreas.herrmann3@amd.com>
    Signed-off-by: default avatarDave Jones <davej@redhat.com>
    a266d9f1
powernow-k8.h 7.93 KB