On 10/05/16 15:37, Tvrtko Ursulin wrote:
On 06/05/16 17:39, Dave Gordon wrote:
On 29/04/16 16:03, Tvrtko Ursulin wrote:
[snip]
+ 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).
I think that if i915.enable_guc_loading == 1 then no error should be
logged. Documentation says that value meand "try to load/use the GuC,
fallback if not available" and to me that means it is not an error and
an informational message only should be logged.
OK, this message is now DRM_INFO
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().
Anyhow the special meanings conveyed in fw_path == NULL and *fw_path ==
0 are imho just too hard to follow. I see it is not your code, but
reworking this looked like an opportunity to clean that up. Never mind.
For fw_path:
== NULL means no firmware needed, not an error.
== "" means the driver actually doesn't know what to load in this
situation - the hardware is not recognised. IMHO this should
be an ERROR, but I've made it just informational now.
== path the file we want.
Those are the only three possibilities, it's set just once according the
hardware type and is constant thereafter. It doesn't depend on the
actual load status. That really isn't very complicated.
+ 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.
Shouldn't the code then update the status variables on suspend/whatever?
Same as above, I find it very hard to follow the logic here.
It proceeds by identifying all the ways in which the loading process can
fail; what's left must be The Path To Success (tm) :)
1. Loading forbidden => fail
2. No firmware wanted => fail
3. No firmware known => fail
4. Firmware not fetched => fail
5. Previous load failed => fail
At this point we commit to trying to load the firmware into the h/w.
Then we try three times to reset-and-load the GuC.
- 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;
- }
Look how many lines of complicated logic this patch removes :)
+ 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.
Yes it needs to be reported, but if we are in best effort mode it should
be informational I think. Depends how you view the errors in the kernel
log - it may be a firmware loading error, but from the point of view of
the system log, it is not an error. Everything still works as intended,
more so, the user has asked us to try and carry on with the alternative.
So the system (log) experienced no error.
OK, I've moved it later, and it's now DRM_ERROR if we're going to return
-EIO (GPU wedged) and DRM_INFO otherwise.
+
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)
Ok but it is still a dead branch, no? Should the HAS_GUC_UCODE guard in
i915_gem_init_hw be removed and let be handled by this code only?
Yep, I've changed the call condition :)
+ } 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.
AFAICS the patch removes the early bailout?!
Also, that's a DEBUG message, so users won't see it by default.
So it is OK to confuse fellow developers? :D
With the new reporting as described above, this message is promoted to
DRM_INFO, but only if enable_guc_submission is not already zero. If GuC
submission is already disabled, we won't report that we're falling back
to execlist mode.
You can still confuse yourself by disabling GuC loading *without* also
disabling GuC submission, but in that case the message should help you
realise you asked for something rather strange :)
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.
My question was, why isn't HAS_GUC_UCODE == IS_SKYLAKE to start with ?
Then when BXT support is added, which will need code changes anyway, we
change HAS_GUC_UCODE only.
Probably because the original definition of HAS_GUC_UCODE() was simply
IS_GEN9() -- POR was that *ALL* Gen9 platforms should have a GuC and
firmware for it. Then someone else added KBL as an exception.
Anyway, we now have BXT support, so the if-else-if condition ladder has
a more obvious structure now :)
.Dave.
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