Re: [PATCH] drm/i915: add missing forcewake put on i915_wa_registers()

["Siluvery, Arun" <arun.siluvery@linux.intel.com>]

On 22/10/2014 08:35, Ville Syrjälä wrote:
> On Tue, Oct 21, 2014 at 07:40:35PM +0200, Daniel Vetter wrote:
>> On Tue, Oct 21, 2014 at 02:58:08PM -0200, Paulo Zanoni wrote:
>>> From: Paulo Zanoni <paulo.r.zanoni@intel.com>
>>>
>>> Otherwise, a simple "cat" to the debugfs file can make the machine use
>>> much more power than needed, and prevent it from runtime suspending.
>>>
>>> Related commit:
>>>
>>>      commit 8452e1d173a16d9812422a2272c4ab0f0ba81057
>>>      Author: Mika Kuoppala <mika.kuoppala@linux.intel.com>
>>>      Date:   Tue Oct 7 17:21:26 2014 +0300
>>>          drm/i915: Build workaround list in ring initialization
>>>
>>> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
>>> Cc: Arun Siluvery <arun.siluvery@linux.intel.com>
>>> Testcase: igt/pm_rpm/debugfs-read
>>> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
>>
>> tbh I'm not even sure we want to do the manual forcewake get here -
>> I915_READ will do it for us, and this is a debug interface. So no one
>> should care about perf. Mika, is that right? If so I'd like to merge the
>> inverse patch which drops the fw_get.
>
> Don't we still need the idle msg disable+poll CSPWRFSM trick here on
> gen8? That also needs forcewake around it.
>

I had a chat with Mika on this yesterday and he seem to agree that 
forcewake is probably not required here. I couldn't send the patch 
yesterday but as per Ville's comments looks like we need forcewake here?

regards
Arun

>> -Daniel
>>
>>> ---
>>>   drivers/gpu/drm/i915/i915_debugfs.c | 1 +
>>>   1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
>>> index 9600285..36a4baa 100644
>>> --- a/drivers/gpu/drm/i915/i915_debugfs.c
>>> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
>>> @@ -2671,6 +2671,7 @@ static int i915_wa_registers(struct seq_file *m, void *unused)
>>>   			   addr, value, mask, read, ok ? "OK" : "FAIL");
>>>   	}
>>>
>>> +	gen6_gt_force_wake_put(dev_priv, FORCEWAKE_ALL);
>>>   	intel_runtime_pm_put(dev_priv);
>>>   	mutex_unlock(&dev->struct_mutex);
>>>
>>> --
>>> 2.1.1
>>>
>>> _______________________________________________
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>>> Intel-gfx@lists.freedesktop.org
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>>
>> --
>> Daniel Vetter
>> Software Engineer, Intel Corporation
>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch
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>