Re: [Intel-gfx] [PATCH v2] drm/i915/gt: prevent forcewake releases during BAR resize

["Das, Nirmoy" <nirmoy.das@linux.intel.com>]

On 3/8/2023 2:36 PM, Andrzej Hajda wrote:
> Tests on DG2 machines show that releasing forcewakes during BAR resize
> results later in forcewake ack timeouts.
Do we have a fdo/issues url for that? Having that as References would be 
nice.
>   Since forcewakes can be realeased
> asynchronously the simplest way to prevent it is to get all forcewakes
> for duration of BAR resizing.
>
> v2: hold rpm as well during resizing (Rodrigo)
>
> Signed-off-by: Andrzej Hajda <andrzej.hajda@intel.com>


Acked-by: Nirmoy Das <nirmoy.das@intel.com>


> ---
> Please ignore resend of v1, my mistake.
>
> Regards
> Andrzej
> ---
>   drivers/gpu/drm/i915/gt/intel_region_lmem.c | 25 +++++++++++++++------
>   1 file changed, 18 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_region_lmem.c b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
> index 89fdfc67f8d1e0..2a3217e2890fc7 100644
> --- a/drivers/gpu/drm/i915/gt/intel_region_lmem.c
> +++ b/drivers/gpu/drm/i915/gt/intel_region_lmem.c
> @@ -54,6 +54,7 @@ static void i915_resize_lmem_bar(struct drm_i915_private *i915, resource_size_t
>   	struct resource *root_res;
>   	resource_size_t rebar_size;
>   	resource_size_t current_size;
> +	intel_wakeref_t wakeref;
>   	u32 pci_cmd;
>   	int i;
>   
> @@ -102,15 +103,25 @@ static void i915_resize_lmem_bar(struct drm_i915_private *i915, resource_size_t
>   		return;
>   	}
>   
> -	/* First disable PCI memory decoding references */
> -	pci_read_config_dword(pdev, PCI_COMMAND, &pci_cmd);
> -	pci_write_config_dword(pdev, PCI_COMMAND,
> -			       pci_cmd & ~PCI_COMMAND_MEMORY);
> +	/*
> +	 * Releasing forcewake during BAR resizing results in later forcewake
> +	 * ack timeouts and former can happen any time - it is asynchronous.
> +	 * Grabbing all forcewakes prevents it.
> +	 */
> +	with_intel_runtime_pm(i915->uncore.rpm, wakeref) {
> +		intel_uncore_forcewake_get(&i915->uncore, FORCEWAKE_ALL);
>   
> -	_resize_bar(i915, GEN12_LMEM_BAR, rebar_size);
> +		/* First disable PCI memory decoding references */
> +		pci_read_config_dword(pdev, PCI_COMMAND, &pci_cmd);
> +		pci_write_config_dword(pdev, PCI_COMMAND,
> +				       pci_cmd & ~PCI_COMMAND_MEMORY);
>   
> -	pci_assign_unassigned_bus_resources(pdev->bus);
> -	pci_write_config_dword(pdev, PCI_COMMAND, pci_cmd);
> +		_resize_bar(i915, GEN12_LMEM_BAR, rebar_size);
> +
> +		pci_assign_unassigned_bus_resources(pdev->bus);
> +		pci_write_config_dword(pdev, PCI_COMMAND, pci_cmd);
> +		intel_uncore_forcewake_put(&i915->uncore, FORCEWAKE_ALL);
> +	}
>   }
>   #else
>   static void i915_resize_lmem_bar(struct drm_i915_private *i915, resource_size_t lmem_size) {}