Re: [PATCH] drm/i915: Hold forcewake for whole of punit communication

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Feb 15, 2017 at 10:41:29AM +0000, Chris Wilson wrote:
> Take the forcewake for punit access and hold it across our waits to
> ensure that the powerwell is not dropped by a spurious sleep.
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_sideband.c | 55 ++++++++++++++++++++++-------------
>  1 file changed, 34 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_sideband.c b/drivers/gpu/drm/i915/intel_sideband.c
> index 9f782b5eb6e6..ce6d166d67ea 100644
> --- a/drivers/gpu/drm/i915/intel_sideband.c
> +++ b/drivers/gpu/drm/i915/intel_sideband.c
> @@ -39,42 +39,55 @@
>  /* Private register write, double-word addressing, non-posted */
>  #define SB_CRWRDA_NP	0x07
>  
> -static int vlv_sideband_rw(struct drm_i915_private *dev_priv, u32 devfn,
> -			   u32 port, u32 opcode, u32 addr, u32 *val)
> +static int vlv_sideband_rw(struct drm_i915_private *dev_priv,
> +			   u32 devfn, u32 port, u32 opcode, u32 addr,
> +			   u32 *val)
>  {
> -	u32 cmd, be = 0xf, bar = 0;
> -	bool is_read = (opcode == SB_MRD_NP || opcode == SB_CRRDDA_NP);
> +	const bool is_read = (opcode == SB_MRD_NP || opcode == SB_CRRDDA_NP);
> +	enum forcewake_domains fw_domains;
> +	int err = 0;
>  
> -	cmd = (devfn << IOSF_DEVFN_SHIFT) | (opcode << IOSF_OPCODE_SHIFT) |
> -		(port << IOSF_PORT_SHIFT) | (be << IOSF_BYTE_ENABLES_SHIFT) |
> -		(bar << IOSF_BAR_SHIFT);
> +	lockdep_assert_held(&dev_priv->sb_lock);
>  
> -	WARN_ON(!mutex_is_locked(&dev_priv->sb_lock));
> +	fw_domains = intel_uncore_forcewake_for_reg(dev_priv,
> +						    VLV_IOSF_DOORBELL_REQ,

The mailbox lives in the display register range, and so doesn't need
forcewake.

> +						    FW_REG_READ | FW_REG_WRITE);
> +	intel_uncore_forcewake_get(dev_priv, fw_domains);
>  
> -	if (intel_wait_for_register(dev_priv,
> -				    VLV_IOSF_DOORBELL_REQ, IOSF_SB_BUSY, 0,
> -				    5)) {
> +	if (intel_wait_for_register_fw(dev_priv,
> +				       VLV_IOSF_DOORBELL_REQ, IOSF_SB_BUSY, 0,
> +				       5)) {
>  		DRM_DEBUG_DRIVER("IOSF sideband idle wait (%s) timed out\n",
>  				 is_read ? "read" : "write");
> -		return -EAGAIN;
> +		err = -EAGAIN;
> +		goto out;
>  	}
>  
> -	I915_WRITE(VLV_IOSF_ADDR, addr);
> -	I915_WRITE(VLV_IOSF_DATA, is_read ? 0 : *val);
> -	I915_WRITE(VLV_IOSF_DOORBELL_REQ, cmd);
> +	I915_WRITE_FW(VLV_IOSF_ADDR, addr);
> +	I915_WRITE_FW(VLV_IOSF_DATA, is_read ? 0 : *val);
> +	I915_WRITE_FW(VLV_IOSF_DOORBELL_REQ,
> +		      (devfn << IOSF_DEVFN_SHIFT) |
> +		      (opcode << IOSF_OPCODE_SHIFT) |
> +		      (port << IOSF_PORT_SHIFT) |
> +		      (0xf << IOSF_BYTE_ENABLES_SHIFT) |
> +		      (0 << IOSF_BAR_SHIFT));
>  
> -	if (intel_wait_for_register(dev_priv,
> -				    VLV_IOSF_DOORBELL_REQ, IOSF_SB_BUSY, 0,
> -				    5)) {
> +
> +	if (intel_wait_for_register_fw(dev_priv,
> +				       VLV_IOSF_DOORBELL_REQ, IOSF_SB_BUSY, 0,
> +				       5)) {
>  		DRM_DEBUG_DRIVER("IOSF sideband finish wait (%s) timed out\n",
>  				 is_read ? "read" : "write");
> -		return -ETIMEDOUT;
> +		err = -ETIMEDOUT;
> +		goto out;
>  	}
>  
>  	if (is_read)
> -		*val = I915_READ(VLV_IOSF_DATA);
> +		*val = I915_READ_FW(VLV_IOSF_DATA);
>  
> -	return 0;
> +out:
> +	intel_uncore_forcewake_put(dev_priv, fw_domains);
> +	return err;
>  }
>  
>  u32 vlv_punit_read(struct drm_i915_private *dev_priv, u32 addr)
> -- 
> 2.11.0
> 
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> Intel-gfx@lists.freedesktop.org
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-- 
Ville Syrjälä
Intel OTC
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