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Re: [PATCH] oprofile: VR5500 performance counter driver

To: Mark Asselstine <mark.asselstine@windriver.com>, Ralf Baechle <ralf@linux-mips.org>
Subject: Re: [PATCH] oprofile: VR5500 performance counter driver
From: Robert Richter <robert.richter@amd.com>
Date: Wed, 25 Feb 2009 17:59:53 +0100
Cc: linux-mips@linux-mips.org, oprofile-list@lists.sf.net
In-reply-to: <1235406394-2650-1-git-send-email-mark.asselstine@windriver.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <1235406394-2650-1-git-send-email-mark.asselstine@windriver.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.5.16 (2007-06-09)
On 23.02.09 11:26:34, Mark Asselstine wrote:
> This is inspired by op_model_mipsxx.c with some modification
> in regards to register layout and overflow handling. This has
> been tested on a NEC VR5500 board and shown to produce sane
> results.

Mark,

I have looked at the differences between the VR5500 code and the
generic in op_model_mipsxx.c. If I am not wrong, only the interrupt
handling is different. This affects only vr5500_reg_setup() and
vr5500_perfcount_handler(). I think it would be better to implement
cpu checks in the generic functions or remap to cpu specific functions
during mipsxx_init(). This extension of the generic code is much more
maintainable. Also, there is less code in the end. See also my
comments below.

-Robert

> 
> Signed-off-by: Mark Asselstine <mark.asselstine@windriver.com>
> 
> diff --git a/arch/mips/oprofile/Makefile b/arch/mips/oprofile/Makefile
> index cfd4b60..977a828 100644
> --- a/arch/mips/oprofile/Makefile
> +++ b/arch/mips/oprofile/Makefile
> @@ -14,4 +14,5 @@ oprofile-$(CONFIG_CPU_MIPS32)               += 
> op_model_mipsxx.o
>  oprofile-$(CONFIG_CPU_MIPS64)                += op_model_mipsxx.o
>  oprofile-$(CONFIG_CPU_R10000)                += op_model_mipsxx.o
>  oprofile-$(CONFIG_CPU_SB1)           += op_model_mipsxx.o
> +oprofile-$(CONFIG_CPU_VR5500)                += op_model_vr5500.o

I could not find a Kconfig option for this.

>  oprofile-$(CONFIG_CPU_RM9000)                += op_model_rm9000.o
> diff --git a/arch/mips/oprofile/common.c b/arch/mips/oprofile/common.c
> index e1bffab..68aad99 100644
> --- a/arch/mips/oprofile/common.c
> +++ b/arch/mips/oprofile/common.c
> @@ -17,6 +17,7 @@
>  
>  extern struct op_mips_model op_model_mipsxx_ops __attribute__((weak));
>  extern struct op_mips_model op_model_rm9000_ops __attribute__((weak));
> +extern struct op_mips_model op_model_vr5500_ops __attribute__((weak));
>  
>  static struct op_mips_model *model;
>  
> @@ -94,6 +95,10 @@ int __init oprofile_arch_init(struct oprofile_operations 
> *ops)
>       case CPU_RM9000:
>               lmodel = &op_model_rm9000_ops;
>               break;
> +
> +     case CPU_R5500:
> +             lmodel = &op_model_vr5500_ops;
> +             break;

Is there a reason for using _vr5500_ instead of _r5500_ for the
function and the filename?

>       };
>  
>  
> diff --git a/arch/mips/oprofile/op_model_vr5500.c 
> b/arch/mips/oprofile/op_model_vr5500.c
> new file mode 100644
> index 0000000..75fae6a
> --- /dev/null
> +++ b/arch/mips/oprofile/op_model_vr5500.c
> @@ -0,0 +1,179 @@
> +/*
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License.  See the file "COPYING" in the main directory of this archive
> + * for more details.
> + *

Copyright statements from op_model_mipsxx.c should be added here.

> + * Copyright (c) 2009 Wind River Systems, Inc.
> + */
> +#include <linux/cpumask.h>
> +#include <linux/oprofile.h>
> +#include <linux/interrupt.h>
> +#include <linux/smp.h>
> +#include <asm/irq_regs.h>
> +
> +#include "op_impl.h"
> +
> +#define M_PERFCTL_EXL                        (1UL      <<  0)
> +#define M_PERFCTL_KERNEL             (1UL      <<  1)
> +#define M_PERFCTL_SUPERVISOR         (1UL      <<  2)
> +#define M_PERFCTL_USER                       (1UL      <<  3)
> +#define M_PERFCTL_INTERRUPT_ENABLE   (1UL      <<  4)
> +#define M_PERFCTL_INTERRUPT          (1UL      <<  5)
> +#define M_PERFCTL_EVENT(event)               (((event) & 0xf)  << 6)
> +#define M_PERFCTL_COUNT_ENABLE               (1UL      <<  10)
> +
> +#define NUM_COUNTERS                    2
> +
> +static int (*save_perf_irq) (void);
> +
> +#define __define_perf_accessors(r, n)                                \
> +                                                                     \
> +     static inline unsigned int r_c0_ ## r ## n(void)                \
> +     {                                                               \
> +             return read_c0_ ## r ## n();                            \
> +     }                                                               \
> +                                                                     \
> +     static inline void w_c0_ ## r ## n(unsigned int value)          \
> +     {                                                               \
> +             write_c0_ ## r ## n(value);                             \
> +     }                                                               \
> +
> +__define_perf_accessors(perfcntr, 0)
> +__define_perf_accessors(perfcntr, 1)
> +
> +__define_perf_accessors(perfctrl, 0)
> +__define_perf_accessors(perfctrl, 1)

I know this code is borrowed, but why not use write/read_c0_perfXXXX()
directly?

> +
> +struct op_mips_model op_model_vr5500_ops;
> +
> +static struct vr5500_register_config {
> +     unsigned int control[NUM_COUNTERS];
> +     unsigned int counter[NUM_COUNTERS];
> +} reg;
> +
> +/* Compute all of the registers in preparation for enabling profiling.  */
> +static void vr5500_reg_setup(struct op_counter_config *ctr)
> +{
> +     int i;
> +     unsigned int counters = NUM_COUNTERS;
> +
> +     /* Compute the performance counter control word.  */
> +     for (i = 0; i < counters; i++) {
> +             reg.control[i] = 0;
> +             reg.counter[i] = 0;
> +
> +             if (!ctr[i].enabled)
> +                     continue;
> +
> +             reg.control[i] = M_PERFCTL_EVENT(ctr[i].event) |
> +                 M_PERFCTL_INTERRUPT_ENABLE | M_PERFCTL_COUNT_ENABLE;
> +             if (ctr[i].kernel)
> +                     reg.control[i] |= M_PERFCTL_KERNEL;
> +             if (ctr[i].user)
> +                     reg.control[i] |= M_PERFCTL_USER;
> +             if (ctr[i].exl)
> +                     reg.control[i] |= M_PERFCTL_EXL;
> +
> +             reg.counter[i] = 0xffffffff - ctr[i].count + 1;
> +     }
> +}
> +
> +/* Program all of the registers in preparation for enabling profiling.  */
> +static void vr5500_cpu_setup(void *args)
> +{
> +     w_c0_perfctrl1(0);
> +     w_c0_perfcntr1(reg.counter[1]);
> +
> +     w_c0_perfctrl0(0);
> +     w_c0_perfcntr0(reg.counter[0]);
> +}
> +
> +/* Start all counters on current CPU */
> +static void vr5500_cpu_start(void *args)
> +{
> +     w_c0_perfctrl1(reg.control[1]);
> +     w_c0_perfctrl0(reg.control[0]);
> +}
> +
> +/* Stop all counters on current CPU */
> +static void vr5500_cpu_stop(void *args)
> +{
> +     w_c0_perfctrl1(0);
> +     w_c0_perfctrl0(0);
> +}
> +
> +static int vr5500_perfcount_handler(void)
> +{
> +     unsigned int control;
> +     unsigned int counter;
> +     int handled = IRQ_NONE;
> +     unsigned int counters = NUM_COUNTERS;
> +
> +     if (cpu_has_mips_r2 && !(read_c0_cause() & (1 << 26)))

Do not use magic numbers.

> +             return handled;
> +
> +     switch (counters) {

Since counters is a fix value the switch/case could be removed.

> +     #define HANDLE_COUNTER(n)                                       \
> +     case n + 1:                                                     \
> +             control = r_c0_perfctrl ## n();                         \
> +             counter = r_c0_perfcntr ## n();                         \
> +             if ((control & M_PERFCTL_INTERRUPT_ENABLE) &&           \
> +                     (control & M_PERFCTL_INTERRUPT)) {              \
> +                     oprofile_add_sample(get_irq_regs(), n);         \
> +                     w_c0_perfcntr ## n(reg.counter[n]);             \
> +                     w_c0_perfctrl ## n(control & ~M_PERFCTL_INTERRUPT); \
> +                     handled = IRQ_HANDLED;                          \
> +             }
> +     HANDLE_COUNTER(1)
> +     HANDLE_COUNTER(0)
> +     }

It is hard to see a loop here. I would like to prefer programming c
instead of macros unless there is a good reason to do so. Also, this
causes a checkpatch error.

> +
> +     return handled;
> +}
> +
> +static void reset_counters(void *arg)
> +{
> +     w_c0_perfctrl1(0);
> +     w_c0_perfcntr1(0);
> +
> +     w_c0_perfctrl0(0);
> +     w_c0_perfcntr0(0);
> +}
> +
> +static int __init vr5500_init(void)
> +{
> +     on_each_cpu(reset_counters, NULL, 1);
> +
> +     switch (current_cpu_type()) {
> +     case CPU_R5500:
> +             op_model_vr5500_ops.cpu_type = "mips/vr5500";
> +             break;
> +
> +     default:
> +             printk(KERN_ERR "Profiling unsupported for this CPU\n");
> +
> +             return -ENODEV;
> +     }
> +
> +     save_perf_irq = perf_irq;
> +     perf_irq = vr5500_perfcount_handler;
> +
> +     return 0;
> +}
> +
> +static void vr5500_exit(void)
> +{
> +     on_each_cpu(reset_counters, NULL, 1);
> +
> +     perf_irq = save_perf_irq;
> +}
> +
> +struct op_mips_model op_model_vr5500_ops = {
> +     .reg_setup = vr5500_reg_setup,
> +     .cpu_setup = vr5500_cpu_setup,
> +     .init = vr5500_init,
> +     .exit = vr5500_exit,
> +     .cpu_start = vr5500_cpu_start,
> +     .cpu_stop = vr5500_cpu_stop,
> +     .num_counters = NUM_COUNTERS,

Please align this vertically.

> +};
> 
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-- 
Advanced Micro Devices, Inc.
Operating System Research Center
email: robert.richter@amd.com


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