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    Subject[PATCH 5.9 447/757] powerpc/tau: Check processor type before enabling TAU interrupt
    Date
    From: Finn Thain <fthain@telegraphics.com.au>

    [ Upstream commit 5e3119e15fed5b9a9a7e528665ff098a4a8dbdbc ]

    According to Freescale's documentation, MPC74XX processors have an
    erratum that prevents the TAU interrupt from working, so don't try to
    use it when running on those processors.

    Fixes: 1da177e4c3f41 ("Linux-2.6.12-rc2")
    Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
    Tested-by: Stan Johnson <userm57@yahoo.com>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/c281611544768e758bd58fe812cf702a5bd2d042.1599260540.git.fthain@telegraphics.com.au
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/kernel/tau_6xx.c | 33 ++++++++++++++-------------------
    arch/powerpc/platforms/Kconfig | 5 ++---
    2 files changed, 16 insertions(+), 22 deletions(-)

    diff --git a/arch/powerpc/kernel/tau_6xx.c b/arch/powerpc/kernel/tau_6xx.c
    index b8d7e7d498e0a..614b5b272d9c6 100644
    --- a/arch/powerpc/kernel/tau_6xx.c
    +++ b/arch/powerpc/kernel/tau_6xx.c
    @@ -40,6 +40,8 @@ static struct tau_temp
    unsigned char grew;
    } tau[NR_CPUS];

    +static bool tau_int_enable;
    +
    #undef DEBUG

    /* TODO: put these in a /proc interface, with some sanity checks, and maybe
    @@ -54,22 +56,13 @@ static struct tau_temp

    static void set_thresholds(unsigned long cpu)
    {
    -#ifdef CONFIG_TAU_INT
    - /*
    - * setup THRM1,
    - * threshold, valid bit, enable interrupts, interrupt when below threshold
    - */
    - mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TIE | THRM1_TID);
    + u32 maybe_tie = tau_int_enable ? THRM1_TIE : 0;

    - /* setup THRM2,
    - * threshold, valid bit, enable interrupts, interrupt when above threshold
    - */
    - mtspr (SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | THRM1_TIE);
    -#else
    - /* same thing but don't enable interrupts */
    - mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | THRM1_TID);
    - mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V);
    -#endif
    + /* setup THRM1, threshold, valid bit, interrupt when below threshold */
    + mtspr(SPRN_THRM1, THRM1_THRES(tau[cpu].low) | THRM1_V | maybe_tie | THRM1_TID);
    +
    + /* setup THRM2, threshold, valid bit, interrupt when above threshold */
    + mtspr(SPRN_THRM2, THRM1_THRES(tau[cpu].high) | THRM1_V | maybe_tie);
    }

    static void TAUupdate(int cpu)
    @@ -142,9 +135,8 @@ static void tau_timeout(void * info)
    local_irq_save(flags);
    cpu = smp_processor_id();

    -#ifndef CONFIG_TAU_INT
    - TAUupdate(cpu);
    -#endif
    + if (!tau_int_enable)
    + TAUupdate(cpu);

    size = tau[cpu].high - tau[cpu].low;
    if (size > min_window && ! tau[cpu].grew) {
    @@ -225,6 +217,9 @@ static int __init TAU_init(void)
    return 1;
    }

    + tau_int_enable = IS_ENABLED(CONFIG_TAU_INT) &&
    + !strcmp(cur_cpu_spec->platform, "ppc750");
    +
    tau_workq = alloc_workqueue("tau", WQ_UNBOUND, 1, 0);
    if (!tau_workq)
    return -ENOMEM;
    @@ -234,7 +229,7 @@ static int __init TAU_init(void)
    queue_work(tau_workq, &tau_work);

    pr_info("Thermal assist unit using %s, shrink_timer: %d ms\n",
    - IS_ENABLED(CONFIG_TAU_INT) ? "interrupts" : "workqueue", shrink_timer);
    + tau_int_enable ? "interrupts" : "workqueue", shrink_timer);
    tau_initialized = 1;

    return 0;
    diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
    index fb7515b4fa9c6..9fe36f0b54c1a 100644
    --- a/arch/powerpc/platforms/Kconfig
    +++ b/arch/powerpc/platforms/Kconfig
    @@ -223,9 +223,8 @@ config TAU
    temperature within 2-4 degrees Celsius. This option shows the current
    on-die temperature in /proc/cpuinfo if the cpu supports it.

    - Unfortunately, on some chip revisions, this sensor is very inaccurate
    - and in many cases, does not work at all, so don't assume the cpu
    - temp is actually what /proc/cpuinfo says it is.
    + Unfortunately, this sensor is very inaccurate when uncalibrated, so
    + don't assume the cpu temp is actually what /proc/cpuinfo says it is.

    config TAU_INT
    bool "Interrupt driven TAU driver (DANGEROUS)"
    --
    2.25.1


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