Re: [Intel-gfx] [PATCH v2] drm/i915/debugfs : PM_REQ and PM_RES registers

[Jani Nikula <jani.nikula@intel.com>]

On Mon, 04 Jan 2021, Saichandana S <saichandana.s@intel.com> wrote:
> From: Saichandana <saichandana.s@intel.com>
>
> PM_REQ register provides the value of the last PM request from PCU to
> Display Engine.PM_RES register provides the value of the last PM
> response from Display Engine to PCU.This debugfs will be used by
> DC9 IGT test to know about "DC9 Ready" status.
>
> B.Spec : 49501, 49502
>
> Signed-off-by: Saichandana <saichandana.s@intel.com>
> ---
>  .../drm/i915/display/intel_display_debugfs.c  | 30 +++++++++++++++++++
>  drivers/gpu/drm/i915/i915_reg.h               |  8 +++++
>  2 files changed, 38 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_display_debugfs.c b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> index cd7e5519ee7d..551fb1a90bb3 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_debugfs.c
> @@ -559,6 +559,36 @@ static int i915_dmc_info(struct seq_file *m, void *unused)
>  	return 0;
>  }
>  
> +static int i915_pm_req_res_info(struct seq_file *m, void *unused)
> +{
> +	struct drm_i915_private *dev_priv = node_to_i915(m->private);

All new code should call the local variable "i915".

> +	struct intel_csr *csr = &dev_priv->csr;
> +	const char *status;
> +
> +	if (!HAS_CSR(dev_priv))
> +		return -ENODEV;
> +	if (!csr->dmc_payload)
> +		return 0;
> +	seq_printf(m, "PM debug request 0 (0x45284): 0x%08x\n",
> +		   intel_de_read(dev_priv, PM_REQ_DBG_0));
> +	seq_printf(m, "PM debug request 1 (0x45288): 0x%08x\n",
> +		   intel_de_read(dev_priv, PM_REQ_DBG_1));
> +	seq_printf(m, "PM debug response 0 (0x4528C): 0x%08x\n",
> +		   intel_de_read(dev_priv, PM_RSP_DBG_0));
> +	seq_printf(m, "PM debug response 1 (0x45290): 0x%08x\n",
> +		   intel_de_read(dev_priv, PM_RSP_DBG_1));

Like I said before [1], do *not* dump the registers. We have userspace
tools for dumping register contents as-is when you need that for debug
purposes. And even the userspace tool can do some register content
parsing. See tools/intel_reg in igt.

The only reason to have a debugfs file is to provide some other, added
value that a register dump can't provide.

[1] http://lore.kernel.org/r/87mtyl8vpu.fsf@intel.com

> +	status = (intel_de_read(dev_priv, PM_RSP_DBG_1) & MASK_DC9_BIT) ? "yes" : "no";

See yesno() in i915_utils.h. You probably don't want the local variable
for the string.

> +
> +	seq_printf(m, "Time to Next Fill = 0x%0x\n",
> +		   (intel_de_read(dev_priv, PM_RSP_DBG_0) & ~MASK_RSP_0));
> +	seq_printf(m, "Time to Next VBI = 0x%0x\n",
> +		   ((intel_de_read(dev_priv, PM_RSP_DBG_0) & MASK_RSP_0)) >> 16);
> +	seq_printf(m, "Selective Exit Latency = 0x%0x\n",
> +		   (intel_de_read(dev_priv, PM_RSP_DBG_1) & MASK_RSP_1));

There's a bunch of unnecessary parenthesis around the 3rd parameter to
seq_printf.

> +	seq_printf(m, "DC9 Ready = %s\n", status);
> +	return 0;
> +}
> +
>  static void intel_seq_print_mode(struct seq_file *m, int tabs,
>  				 const struct drm_display_mode *mode)
>  {
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 0023c023f472..3e9ed555f928 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -371,6 +371,14 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
>  #define VLV_G3DCTL		_MMIO(0x9024)
>  #define VLV_GSCKGCTL		_MMIO(0x9028)
>  
> +#define PM_REQ_DBG_0		_MMIO(0x45284)
> +#define PM_REQ_DBG_1		_MMIO(0x45288)
> +#define PM_RSP_DBG_0		_MMIO(0x4528C)
> +#define PM_RSP_DBG_1		_MMIO(0x45290)
> +#define MASK_RSP_0		(0xFFFF << 16)
> +#define MASK_RSP_1		(7 << 0)
> +#define MASK_DC9_BIT		(1 << 17)

This is a random location in i915_reg.h, out of place.

Please also read the big comment near the top of this file.

BR,
Jani.


> +
>  #define GEN6_MBCTL		_MMIO(0x0907c)
>  #define   GEN6_MBCTL_ENABLE_BOOT_FETCH	(1 << 4)
>  #define   GEN6_MBCTL_CTX_FETCH_NEEDED	(1 << 3)

-- 
Jani Nikula, Intel Open Source Graphics Center
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