linux-kernel - Re: [PATCH 2/4] drm/v3d: Add a little debugfs entry for measuring the core clock.

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Message-ID: <20181009152640.791c709d@bbrezillon>
Date:   Tue, 9 Oct 2018 15:26:40 +0200
From:   Boris Brezillon <boris.brezillon@...tlin.com>
To:     Eric Anholt <eric@...olt.net>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] drm/v3d: Add a little debugfs entry for measuring
 the core clock.

On Fri, 28 Sep 2018 16:21:24 -0700
Eric Anholt <eric@...olt.net> wrote:

> This adds just enough performance counter support to measure the
> clock.  We don't have linux kernel drivers for the clock driving the
> HW, and this was useful for determining that the V3D HW is running on
> a slow clock, not that the driver was slow.
> 
> Signed-off-by: Eric Anholt <eric@...olt.net>

Reviewed-by: Boris Brezillon <boris.brezillon@...tlin.com>

> ---
>  drivers/gpu/drm/v3d/v3d_debugfs.c | 35 +++++++++++++++++++++++++++++++
>  drivers/gpu/drm/v3d/v3d_regs.h    | 30 ++++++++++++++++++++++++++
>  2 files changed, 65 insertions(+)
> 
> diff --git a/drivers/gpu/drm/v3d/v3d_debugfs.c b/drivers/gpu/drm/v3d/v3d_debugfs.c
> index 4db62c545748..d48008adb085 100644
> --- a/drivers/gpu/drm/v3d/v3d_debugfs.c
> +++ b/drivers/gpu/drm/v3d/v3d_debugfs.c
> @@ -176,9 +176,44 @@ static int v3d_debugfs_bo_stats(struct seq_file *m, void *unused)
>  	return 0;
>  }
>  
> +static int v3d_measure_clock(struct seq_file *m, void *unused)
> +{
> +	struct drm_info_node *node = (struct drm_info_node *)m->private;
> +	struct drm_device *dev = node->minor->dev;
> +	struct v3d_dev *v3d = to_v3d_dev(dev);
> +	uint32_t cycles;
> +	int core = 0;
> +	int measure_ms = 1000;
> +
> +	if (v3d->ver >= 40) {
> +		V3D_CORE_WRITE(core, V3D_V4_PCTR_0_SRC_0_3,
> +			       V3D_SET_FIELD(V3D_PCTR_CYCLE_COUNT,
> +					     V3D_PCTR_S0));
> +		V3D_CORE_WRITE(core, V3D_V4_PCTR_0_CLR, 1);
> +		V3D_CORE_WRITE(core, V3D_V4_PCTR_0_EN, 1);
> +	} else {
> +		V3D_CORE_WRITE(core, V3D_V3_PCTR_0_PCTRS0,
> +			       V3D_PCTR_CYCLE_COUNT);
> +		V3D_CORE_WRITE(core, V3D_V3_PCTR_0_CLR, 1);
> +		V3D_CORE_WRITE(core, V3D_V3_PCTR_0_EN,
> +			       V3D_V3_PCTR_0_EN_ENABLE |
> +			       1);
> +	}
> +	msleep(measure_ms);
> +	cycles = V3D_CORE_READ(core, V3D_PCTR_0_PCTR0);
> +
> +	seq_printf(m, "cycles: %d (%d.%d Mhz)\n",
> +		   cycles,
> +		   cycles / (measure_ms * 1000),
> +		   (cycles / (measure_ms * 100)) % 10);
> +
> +	return 0;
> +}
> +
>  static const struct drm_info_list v3d_debugfs_list[] = {
>  	{"v3d_ident", v3d_v3d_debugfs_ident, 0},
>  	{"v3d_regs", v3d_v3d_debugfs_regs, 0},
> +	{"measure_clock", v3d_measure_clock, 0},
>  	{"bo_stats", v3d_debugfs_bo_stats, 0},
>  };
>  
> diff --git a/drivers/gpu/drm/v3d/v3d_regs.h b/drivers/gpu/drm/v3d/v3d_regs.h
> index 854046565989..c3a5e4e44f73 100644
> --- a/drivers/gpu/drm/v3d/v3d_regs.h
> +++ b/drivers/gpu/drm/v3d/v3d_regs.h
> @@ -267,6 +267,36 @@
>  # define V3D_PTB_BXCF_RWORDERDISA                      BIT(1)
>  # define V3D_PTB_BXCF_CLIPDISA                         BIT(0)
>  
> +#define V3D_V3_PCTR_0_EN                               0x00674
> +#define V3D_V3_PCTR_0_EN_ENABLE                        BIT(31)
> +#define V3D_V4_PCTR_0_EN                               0x00650
> +/* When a bit is set, resets the counter to 0. */
> +#define V3D_V3_PCTR_0_CLR                              0x00670
> +#define V3D_V4_PCTR_0_CLR                              0x00654
> +#define V3D_PCTR_0_OVERFLOW                            0x00658
> +
> +#define V3D_V3_PCTR_0_PCTRS0                           0x00684
> +#define V3D_V3_PCTR_0_PCTRS15                          0x00660
> +#define V3D_V3_PCTR_0_PCTRSX(x)                        (V3D_V3_PCTR_0_PCTRS0 + \
> +							4 * (x))
> +/* Each src reg muxes four counters each. */
> +#define V3D_V4_PCTR_0_SRC_0_3                          0x00660
> +#define V3D_V4_PCTR_0_SRC_28_31                        0x0067c
> +# define V3D_PCTR_S0_MASK                              V3D_MASK(6, 0)
> +# define V3D_PCTR_S0_SHIFT                             0
> +# define V3D_PCTR_S1_MASK                              V3D_MASK(14, 8)
> +# define V3D_PCTR_S1_SHIFT                             8
> +# define V3D_PCTR_S2_MASK                              V3D_MASK(22, 16)
> +# define V3D_PCTR_S2_SHIFT                             16
> +# define V3D_PCTR_S3_MASK                              V3D_MASK(30, 24)
> +# define V3D_PCTR_S3_SHIFT                             24
> +# define V3D_PCTR_CYCLE_COUNT                          32
> +
> +/* Output values of the counters. */
> +#define V3D_PCTR_0_PCTR0                               0x00680
> +#define V3D_PCTR_0_PCTR31                              0x006fc
> +#define V3D_PCTR_0_PCTRX(x)                            (V3D_PCTR_0_PCTR0 + \
> +							4 * (x))
>  #define V3D_GMP_STATUS                                 0x00800
>  # define V3D_GMP_STATUS_GMPRST                         BIT(31)
>  # define V3D_GMP_STATUS_WR_COUNT_MASK                  V3D_MASK(30, 24)