Re: [PATCH 2/5] drm/i915: Notify user about outdated dmc firmware

[Animesh Manna <animesh.manna@intel.com>]

On 10/8/2015 5:53 PM, Mika Kuoppala wrote:
> Animesh Manna <animesh.manna@intel.com> writes:
>
>> On 9/21/2015 2:00 PM, Mika Kuoppala wrote:
>>> Jani Nikula <jani.nikula@linux.intel.com> writes:
>>>
>>>> On Fri, 18 Sep 2015, Mika Kuoppala <mika.kuoppala@linux.intel.com> wrote:
>>>>> If csr/dmc firmware is known to be outdated, notify
>>>>> user.
>>>> What would break if we requested a firmware version that works? Or we've
>>>> made it so that we only request the major version because there's not
>>>> supposed to be changes like this between minor versions...?
>>>>
>>> I guess the question is more of a what should we do
>>> if there is only outdated (known bad) firmware available.
>>>
>>> Refuse to load and limb onwards, or return with error code
>>> on driver init.
>>>
>>> Latter would force firmware and version to be mandatory and the
>>> version to be tightly coupled to kernel driver version.
>> A softlink is used to use recommended firmware for dmc and the same information is published through 01.org for the firmware user.
>> Imo, we should not have this kind of hack in code which will change over time and this is responsibility of repo-owner to link correct recommended firmware for new kernel update.
>>
> On machines that had 1.19 symlinked, in filesystem, execlist submission
> sometimes broke due to interrupt delivery problem. To reach a conclusion
> that it was csr firmware, before 1.21 was out, took quite amount of work.
>
> I bet there are still machines with 1.19 only, and we get to
> wade through error states trying to connect the dots.
>
> The dmc/csr firmware is part of our driver functionality. Apparently
> it is very tightly coupled to our driver functionality as it can
> break things outside of its own domain.
>
> And currently it is loosely coupled black box with our driver,
> through symlink, accepting any version that happens to be in customers filesystem.
>
> So we recommend latest in website and end up in a situation
> that user gets what happens to be in filesystem. Even a known
> broken version? And we will keep debugging these problems caused by
> broken version? I don't want any more dimensions in our triaging
> space, the distributio/firmware version dimension.
>
> Symlink also means that bisectability is very close to worthless on these
> kind of bugs. Both in our machines and also on customers. We have
> loosely coupled, black box entity, affecting our driver depending
> on customers filesystem. Symlink threw that valuable tool out, and
> we gained what?
>
> So we are left with triaging. Which is true detective work as there are
> no traces of firmware versions nor loading success/fails on
> logs/error states.
>
>  From where I look at, the version blacklist is not a hack. It is a cure.

I completely understand your concern and we discussed a lot on same during firmware naming
convention and finally decided to have symlink.

If we really want to tightly couple firmware and driver then imo putting exact firmware name
will be better option.

Next I saw your subsequent patch where you are not loading the firmware if it is older than 1.21.
http://lists.freedesktop.org/archives/intel-gfx/2015-September/076422.html
Curious to know the gpu-hang issue present for any version less than 1.21.

-Animesh


>
> -Mika
>
>> -Animesh
>>
>>> -Mika
>>>
>>>> BR,
>>>> Jani.
>>>>
>>>>
>>>>
>>>>> Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
>>>>> ---
>>>>>    drivers/gpu/drm/i915/intel_csr.c | 9 +++++++++
>>>>>    1 file changed, 9 insertions(+)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/i915/intel_csr.c b/drivers/gpu/drm/i915/intel_csr.c
>>>>> index 58edc3f..73807c3 100644
>>>>> --- a/drivers/gpu/drm/i915/intel_csr.c
>>>>> +++ b/drivers/gpu/drm/i915/intel_csr.c
>>>>> @@ -45,6 +45,9 @@
>>>>>    
>>>>>    MODULE_FIRMWARE(I915_CSR_SKL);
>>>>>    
>>>>> +#define RECOMMENDED_FW_MAJOR		1
>>>>> +#define RECOMMENDED_FW_MINOR		21
>>>>> +
>>>>>    /*
>>>>>    * SKL CSR registers for DC5 and DC6
>>>>>    */
>>>>> @@ -387,6 +390,12 @@ static void finish_csr_load(const struct firmware *fw, void *context)
>>>>>    
>>>>>    	DRM_DEBUG_KMS("Finished loading %s v%u.%u\n", dev_priv->csr.fw_path,
>>>>>    		      csr->dmc_ver_major, csr->dmc_ver_minor);
>>>>> +
>>>>> +	if (csr->dmc_ver_major < RECOMMENDED_FW_MAJOR ||
>>>>> +	    csr->dmc_ver_minor < RECOMMENDED_FW_MINOR)
>>>>> +		DRM_INFO("Outdated dmc firmware found, please upgrade to %u.%u or newer\n",
>>>>> +			 RECOMMENDED_FW_MAJOR, RECOMMENDED_FW_MINOR);
>>>>> +
>>>>>    out:
>>>>>    	if (fw_loaded)
>>>>>    		intel_runtime_pm_put(dev_priv);
>>>>> -- 
>>>>> 2.1.4
>>>>>
>>>>> _______________________________________________
>>>>> Intel-gfx mailing list
>>>>> Intel-gfx@lists.freedesktop.org
>>>>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>>>> -- 
>>>> Jani Nikula, Intel Open Source Technology Center
>>> _______________________________________________
>>> Intel-gfx mailing list
>>> Intel-gfx@lists.freedesktop.org
>>> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

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