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

[Das, Nirmoy]

On 3/9/2023 8:54 AM, Andrzej Hajda wrote:
> On 08.03.2023 18:29, Das, Nirmoy wrote:
>>
>> 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.
>
> The patch is result of issue reported internally, but...grepping 
> bugtracker I've found potential candidates:
>
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/6530
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/7853
>
> Maybe it would be good to add them on merge.

Works for me.


Thanks,

Nirmoy

> Anyway thx for a-b.
>
> Regards
> Andrzej
>
>>>   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 at intel.com>
>>
>>
>> Acked-by: Nirmoy Das <nirmoy.das at 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) {}
>