[Intel-gfx] [PATCH v2 1/5] drm/i915/guc: add enable_guc_loading parameter
Dave Gordon
david.s.gordon at intel.com
Fri May 6 16:39:21 UTC 2016
On 29/04/16 16:03, Tvrtko Ursulin wrote:
>
> Hi,
>
> On 27/04/16 19:03, Dave Gordon wrote:
>> Split the function of "enable_guc_submission" into two separate
>> options. The new one ("enable_guc_loading") controls only the
>> *fetching and loading* of the GuC firmware image. The existing
>> one is redefined to control only the *use* of the GuC for batch
>> submission once the firmware is loaded.
>>
>> In addition, the degree of control has been refined from a simple
>> bool to an integer key, allowing several options:
>> -1 (default) whatever the platform default is
>> 0 DISABLE don't load/use the GuC
>> 1 BEST EFFORT try to load/use the GuC, fallback if not available
>> 2 REQUIRE must load/use the GuC, else leave the GPU wedged
>>
>> The new platform default (as coded here) will be to attempt to
>> load the GuC iff the device has a GuC that requires firmware,
>> but not yet to use it for submission. A later patch will change
>> to enable it if appropriate.
>>
>> Signed-off-by: Dave Gordon <david.s.gordon at intel.com>
>> ---
>> drivers/gpu/drm/i915/i915_gem.c | 1 -
>> drivers/gpu/drm/i915/i915_guc_submission.c | 4 +-
>> drivers/gpu/drm/i915/i915_params.c | 14 ++++-
>> drivers/gpu/drm/i915/i915_params.h | 3 +-
>> drivers/gpu/drm/i915/intel_guc_loader.c | 98
>> ++++++++++++++++--------------
>> drivers/gpu/drm/i915/intel_uncore.c | 2 +-
>> 6 files changed, 70 insertions(+), 52 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_gem.c
>> b/drivers/gpu/drm/i915/i915_gem.c
>> index d493e79..b04effc 100644
>> --- a/drivers/gpu/drm/i915/i915_gem.c
>> +++ b/drivers/gpu/drm/i915/i915_gem.c
>> @@ -4910,7 +4910,6 @@ int i915_gem_init_engines(struct drm_device *dev)
>> ret = intel_guc_ucode_load(dev);
>> if (ret) {
>> DRM_ERROR("Failed to initialize GuC, error %d\n", ret);
>> - ret = -EIO;
>> goto out;
>> }
>> }
>> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c
>> b/drivers/gpu/drm/i915/i915_guc_submission.c
>> index 72d6665..42d2efa 100644
>> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
>> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
>> @@ -970,7 +970,7 @@ int intel_guc_suspend(struct drm_device *dev)
>> struct intel_context *ctx;
>> u32 data[3];
>>
>> - if (!i915.enable_guc_submission)
>> + if (guc->guc_fw.guc_fw_load_status != GUC_FIRMWARE_SUCCESS)
>> return 0;
>>
>> ctx = dev_priv->kernel_context;
>> @@ -996,7 +996,7 @@ int intel_guc_resume(struct drm_device *dev)
>> struct intel_context *ctx;
>> u32 data[3];
>>
>> - if (!i915.enable_guc_submission)
>> + if (guc->guc_fw.guc_fw_load_status != GUC_FIRMWARE_SUCCESS)
>> return 0;
>
> Not terribly important and probably predates your work, but just spotted
> how this reads very redundant - guc->guc_fw.guc_fw_something, while it
> could be much more readable as guc->fw.load_status. Observation only.
That's almost the naming we had in the days when we had a generic
(non-GuC-specific) firmware loader. But when that was rejected, each
custom version had all the variables qualified with the specific target,
hence the redundant naming :(
[snip]
>> --- a/drivers/gpu/drm/i915/intel_guc_loader.c
>> +++ b/drivers/gpu/drm/i915/intel_guc_loader.c
>> @@ -387,49 +387,37 @@ int intel_guc_ucode_load(struct drm_device *dev)
>> {
>> struct drm_i915_private *dev_priv = dev->dev_private;
>> struct intel_guc_fw *guc_fw = &dev_priv->guc.guc_fw;
>> + const char *fw_path = guc_fw->guc_fw_path;
>> int retries, err = 0;
>>
>> - if (!i915.enable_guc_submission)
>> - return 0;
>> -
>> - DRM_DEBUG_DRIVER("GuC fw status: fetch %s, load %s\n",
>> + DRM_DEBUG_DRIVER("GuC fw status: path %s, fetch %s, load %s\n",
>> + fw_path,
>> intel_guc_fw_status_repr(guc_fw->guc_fw_fetch_status),
>> intel_guc_fw_status_repr(guc_fw->guc_fw_load_status));
>
> Should load status be anything other than GUC_FIRMWARE_NONE here?
During resume, it *could* be FAIL, meaning we've tried to load it before
and it didn't work then. In that case we won't try again, as presumably
it still won't work.
>> - direct_interrupts_to_host(dev_priv);
>> + /* Loading forbidden, or no firmware to load? */
>> + if (!i915.enable_guc_loading)
>
> Nitpick, == 0 would perhaps make it more obvious this is not a boolean.
But here we are specifically choosing to treat it as a boolean. This
reads: if GuC loading is NOT enabled (i.e. IS disabled) ...
The value 0 for disabled was not accidental. And note we don't create
#defines for this sort of kernel parameter, because you have to give a
literal constant on the kernel command line.
>> + goto fail;
>> + if (fw_path == NULL)
>> + goto fail;
>> + if (*fw_path == '\0') {
>> + DRM_ERROR("No GuC firmware known for this platform\n");
>
> It is not an error unless i915.enable_guc_loading == 2, no? And if best
> effort then it is probably debug or informational.
No, it's still an ERROR. You're running the driver on a platform for
which we don't know what firmware is required. That probably means an
old driver on new hardware, so it might not work at all. You can
suppress the error by setting i915.enable_guc_loading=0 if you want to
try this version of the driver anyway. Also note the difference between
path == NULL (no GuC, or no firmware required => not an error) vs. path
== "" (has GuC, presumably needs firmware, but we don't know where to
look => ERROR).
> Also, don't the checks against fw_path (together with the error or debug
> message) belong in the fw fetch function? If they are invalid fw fetch
> would have failed and this function would be able to inspect the high
> level status of that step here, no?
The checks are done in intel_guc_ucode_init(), before fw_fetch() is even
called; but that function is void, so can't return failure. (Also, we
originally supported asynchronous loading, which also can't return
failure). So this function will get called even when we already know
that we haven't got any firmware to load, and these tests are indeed
checking the high-level status from _init().
>> + goto fail;
>> + }
>>
>> - if (guc_fw->guc_fw_fetch_status == GUC_FIRMWARE_NONE)
>> - return 0;
>> + /* Fetch failed, or already fetched but failed to load? */
>> + if (guc_fw->guc_fw_fetch_status != GUC_FIRMWARE_SUCCESS)
>> + goto fail;
>> + if (guc_fw->guc_fw_load_status == GUC_FIRMWARE_FAIL)
>> + goto fail;
>
> Leads back to the question of load status in this function. So it is
> expected we always enter here with load status of none? Is it possible
> to get here with the firmware already loaded already?
Not *actually* loaded, because it's been erased by poweroff. But the
status tracking variables are persistent, so they reflect the last
attempt. So on resume, we actually expect "SUCCESS" at this point, and
therefore change it back to PENDING below.
>> - if (guc_fw->guc_fw_fetch_status == GUC_FIRMWARE_SUCCESS &&
>> - guc_fw->guc_fw_load_status == GUC_FIRMWARE_FAIL)
>> - return -ENOEXEC;
>> + direct_interrupts_to_host(dev_priv);
>>
>> guc_fw->guc_fw_load_status = GUC_FIRMWARE_PENDING;
>>
>> - DRM_DEBUG_DRIVER("GuC fw fetch status %s\n",
>> - intel_guc_fw_status_repr(guc_fw->guc_fw_fetch_status));
>> -
>> - switch (guc_fw->guc_fw_fetch_status) {
>> - case GUC_FIRMWARE_FAIL:
>> - /* something went wrong :( */
>> - err = -EIO;
>> - goto fail;
>> -
>> - case GUC_FIRMWARE_NONE:
>> - case GUC_FIRMWARE_PENDING:
>> - default:
>> - /* "can't happen" */
>> - WARN_ONCE(1, "GuC fw %s invalid guc_fw_fetch_status %s [%d]\n",
>> - guc_fw->guc_fw_path,
>> - intel_guc_fw_status_repr(guc_fw->guc_fw_fetch_status),
>> - guc_fw->guc_fw_fetch_status);
>> - err = -ENXIO;
>> - goto fail;
>> -
>> - case GUC_FIRMWARE_SUCCESS:
>> - break;
>> - }
>> + DRM_DEBUG_DRIVER("GuC fw status: fetch %s, load %s\n",
>> + intel_guc_fw_status_repr(guc_fw->guc_fw_fetch_status),
>> + intel_guc_fw_status_repr(guc_fw->guc_fw_load_status));
>>
>> err = i915_guc_submission_init(dev);
>> if (err)
>> @@ -483,6 +471,7 @@ int intel_guc_ucode_load(struct drm_device *dev)
>>
>> fail:
>> DRM_ERROR("GuC firmware load failed, err %d\n", err);
>
> Same as above I think error must be dependent on the requested mode.
> Some customers are very sensitive to errors which are not really errors
> so it is bad to log them when they are not.
No, it's still an ERROR. enable_guc_loading must be nonzero, so we've
been asked to *try* to load the GuC. If the load fails, that means
broken hardware or a corrupt firmware blob, or some other form of system
misconfiguration. Even if we're going to fall back to execlist mode,
that needs to be reported; for example, it may mean that SLPC is
disabled. The user can avoid the error by booting with GuC loading
disabled, but they should probably fix the problem instead.
>> +
>> if (guc_fw->guc_fw_load_status == GUC_FIRMWARE_PENDING)
>> guc_fw->guc_fw_load_status = GUC_FIRMWARE_FAIL;
>>
>> @@ -490,6 +479,29 @@ int intel_guc_ucode_load(struct drm_device *dev)
>> i915_guc_submission_disable(dev);
>> i915_guc_submission_fini(dev);
>>
>> + /*
>> + * We've failed to load the firmware :(
>> + *
>> + * Decide whether to disable GuC submission and fall back to
>> + * execlist mode, and whether to hide the error by returning
>> + * zero or to return -EIO, which the caller will treat as a
>> + * nonfatal error (i.e. it doesn't prevent driver load, but
>> + * marks the GPU as wedged until reset).
>> + */
>> + if (i915.enable_guc_loading > 1) {
>> + err = -EIO;
>> + } else if (HAS_GUC_SCHED(dev) && !HAS_GUC_UCODE(dev)) {
>> + return 0;
>
> i915_gem_init_hw already guards the call to intel_guc_ucode_load with
> HAS_GUC_UCODE so at the moment at least this is a dead branch.
>
> I don't even understand what is this branch supposed to do? How can
> there be a platform with no guc fw but guc scheduling?
Imagine a GuC with firmware in ROM :) Or at least flash ...
(it already has a BootROM)
>> + } else if (i915.enable_guc_submission > 1) {
>> + err = -EIO;
>> + } else {
>> + err = 0;
>> + }
>> +
>> + i915.enable_guc_submission = 0;
>> +
>> + DRM_DEBUG_DRIVER("falling back to execlist mode, err %d\n", err);
>> +
>
> This would log when i915.enable_guc_loading is set to 0 which would be
> confusing. I think in this case the function should bail out much earlier.
That was tested right back at the top of the function! It bailed out
very early, so you can't get here with GuC loading disabled.
Also, that's a DEBUG message, so users won't see it by default.
>> return err;
>> }
>>
>> @@ -631,8 +643,11 @@ void intel_guc_ucode_init(struct drm_device *dev)
>> struct intel_guc_fw *guc_fw = &dev_priv->guc.guc_fw;
>> const char *fw_path;
>>
>> - if (!HAS_GUC_SCHED(dev))
>> - i915.enable_guc_submission = false;
>> + /* A negative value means "use platform default" */
>> + if (i915.enable_guc_loading < 0)
>> + i915.enable_guc_loading = HAS_GUC_UCODE(dev);
>> + if (i915.enable_guc_submission < 0)
>> + i915.enable_guc_submission = HAS_GUC_SCHED(dev);
>
> With this setup currently there is no difference between -1 and 1. But I
> can assume maybe in the future we could have -1 mean 2 on some platform
> which would then justify having four possible values for each?
Yes. 0, 1, and 2 are "user preference". -1 is "system's choice". So
there *is* a difference between -1 and 1, because -1 means the same as 0
on non-GuC platforms, but the same as 1 on those that have a GuC, or
could mean the same as 2 on GuC-only platforms.
>> if (!HAS_GUC_UCODE(dev)) {
>> fw_path = NULL;
>> @@ -641,26 +656,21 @@ void intel_guc_ucode_init(struct drm_device *dev)
>> guc_fw->guc_fw_major_wanted = 6;
>> guc_fw->guc_fw_minor_wanted = 1;
>> } else {
>> - i915.enable_guc_submission = false;
>> fw_path = ""; /* unknown device */
>> }
>
> Confusing block, HAS_GUC_UCODE is defined as (IS_GEN9(dev) &&
> !IS_KABYLAKE(dev)) but then here we only support SKL here. Why the
> former is then not just IS_SKYLAKE?
>
> When BXT support is added this still needs to be modified and would only
> save touching HAS_GUC_UCODE in the header. But it must be a better reason?
I don't see anything confusing. The logic does not depend on how
somebody has defined HAS_GUC_UCODE(), and we shouldn't assume any
relation between it and the platform macros. What it says here is:
1. if this platform *doesn't* have GuC firmware, fw_path is NULL
2a. else if this is SKYLAKE, look for f/w version 6.1
2b. (repeat 2a for each supported platform)
3. (else) unknown device, path is "" which triggers ERROR later.
Imagine a SKL version with GuC uCode in ROM - the HAS_GUC_UCODE() test
must take precedence.
>> - if (!i915.enable_guc_submission)
>> - return;
>> -
>> guc_fw->guc_dev = dev;
>> guc_fw->guc_fw_path = fw_path;
>> guc_fw->guc_fw_fetch_status = GUC_FIRMWARE_NONE;
>> guc_fw->guc_fw_load_status = GUC_FIRMWARE_NONE;
>>
>> + /* Early (and silent) return if GuC loading is disabled */
>> + if (!i915.enable_guc_loading)
>> + return;
>> if (fw_path == NULL)
>> return;
>> -
>> - if (*fw_path == '\0') {
>> - DRM_ERROR("No GuC firmware known for this platform\n");
>> - guc_fw->guc_fw_fetch_status = GUC_FIRMWARE_FAIL;
>> + if (*fw_path == '\0')
>> return;
>> - }
>
> I also do not understand the complications with fw_path (either NULL or
> ""). In the two cases fetch status will be either none or fail,
> respectively, which will equally cause intel_guc_ucode_load to hit the
> failure path (fw_fetch_status != success).
>
> So Is it really required for the fw_path to can either be NULL or ""?
As mentioned before, it's so that the status gets propagated from
_init() to _load(). A Previous Reviewer didn't like issuing errors here,
so the error report got deferred until we actually try to load the
firmware. (Also, someday, we might reenable asynchronous (deferred)
firmware loading. especially on Android).
>> guc_fw->guc_fw_fetch_status = GUC_FIRMWARE_PENDING;
>> DRM_DEBUG_DRIVER("GuC firmware pending, path %s\n", fw_path);
>> diff --git a/drivers/gpu/drm/i915/intel_uncore.c
>> b/drivers/gpu/drm/i915/intel_uncore.c
>> index 4f1dfe6..df698d7 100644
>> --- a/drivers/gpu/drm/i915/intel_uncore.c
>> +++ b/drivers/gpu/drm/i915/intel_uncore.c
>> @@ -1758,7 +1758,7 @@ int intel_guc_reset(struct drm_i915_private
>> *dev_priv)
>> int ret;
>> unsigned long irqflags;
>>
>> - if (!i915.enable_guc_submission)
>> + if (!HAS_GUC_UCODE(dev_priv))
>> return -EINVAL;
>
> What if HAS_GUC_UCODE is true but the i915.load_guc_firmware has been
> set to zero? Should it skip the reset in that case as well?
Probably not. This test should probably be HAS_GUC(), regardless of
whether it has f/w or whether you want the f/w loaded. But there isn't
any such macro, so this was the closest.
.Dave.
>> intel_uncore_forcewake_get(dev_priv, FORCEWAKE_ALL);
>>
>
> Regards,
>
> Tvrtko
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