Re: [PATCH] malta4kec hang in calibrate_delay fix

["Kevin D. Kissell" <kevink@mips.com>]

The 4KEc is a MIPS32 Release 2 processor, for which the implementation
of the Cause.TI bit (bit 30) is required.  You may have a defective board
or a bad FPGA bitfile.  Please work with your support contacts at MIPS
to verify that this is not the case.  It may also be that there's something more
subtle going on in the interrupt processing, such that the Cause.TI bit is being
cleared before it can be sampled by the code you've changed.  But while the
patch below presumably solves the symptoms of your problem, I really
don't think that a kernel hack based on detecting CoreFPA3 is an appropriate
solution.  I work every day with Malta/CoreFPGA3 bitfiles and have not
seen Cause.TI fail to function in any of the Release 2 core bitfiles I've used.

            Regards,

            Kevin K.

----- Original Message ----- 
From: "yshi" <yang.shi@windriver.com>
To: <linux-mips@linux-mips.org>
Sent: Tuesday, September 04, 2007 10:52 AM
Subject: [PATCH] malta4kec hang in calibrate_delay fix


> perfmon2 patch changed timer interrupt handler of malta board.
> When kernel handles timer interrupt, interrupt handler will read 30 bit
> of cause register. If this bit is zero, timer interrupt handler will
> exit, won't really handle interrupt. Because Malta 4kec board's core
> revision is CoreFPGA-3, this core's cause register doesn't implement 30
> bit, so kernel always read zero from this bit. This will cause kernel
> hang in calibrate_delay.
> 
> Signed-off-by: Yang Shi <yang.shi@windriver.com>
> ---
> b/arch/mips/mips-boards/generic/time.c |   17 ++++++++++++-----
> 1 file changed, 12 insertions(+), 5 deletions(-)
> ---
> 
> --- a/arch/mips/mips-boards/generic/time.c
> +++ b/arch/mips/mips-boards/generic/time.c
> @@ -136,11 +136,13 @@ irqreturn_t mips_timer_interrupt(int irq
> #else /* CONFIG_MIPS_MT_SMTC */
>       int r2 = cpu_has_mips_r2;
> 
> -       if (handle_perf_irq(r2))
> -               goto out;
> +       if (mips_revision_corid != MIPS_REVISION_CORID_CORE_FPGA3) {
> +               if (handle_perf_irq(r2))
> +                       goto out;
> 
> -       if (r2 && ((read_c0_cause() & (1 << 30)) == 0))
> -               goto out;
> +               if (r2 && ((read_c0_cause() & (1 << 30)) == 0))
> +                       goto out;
> +       }
> 
>       if (cpu == 0) {
>               /*
> @@ -294,7 +296,12 @@ void __init plat_timer_setup(struct irqa
>       {
>               if (cpu_has_vint)
>                       set_vi_handler(cp0_compare_irq, mips_timer_dispatch);
> -               mips_cpu_timer_irq = MIPS_CPU_IRQ_BASE + cp0_compare_irq;
> +
> +               if (mips_revision_corid != MIPS_REVISION_CORID_CORE_FPGA3)
> +                       mips_cpu_timer_irq = MIPS_CPU_IRQ_BASE + 
> cp0_compare_irq;
> +               else
> +                       mips_cpu_timer_irq = MIPS_CPU_IRQ_BASE +
> +                                            CP0_LEGACY_COMPARE_IRQ;
>       }
> 
>       /* we are using the cpu counter for timer interrupts */
> 
>