[Intel-gfx] [PATCH 2/3] drm/i915/guc: Handle interrupt based logging with lack of SSE4.1, relay and other setup

[Michał Winiarski]

On Wed, Jan 31, 2018 at 11:44:38AM +0530, Sagar Arun Kamble wrote:
> On some systems like skl-gvtdvm, SSE4.1 movntdqa might not be available.
> movntdqa is needed for efficient capture of the logs from uncached GuC
> log buffer. GuC init was tied with this support and other setup needed
> for interrupt based GuC log capture like relay channel/file support and
> uncached mapping support. With this patch, GuC init is now unblocked from
> lack of this support.
> SSE and relay support init/fini is now being done by new functions
> intel_guc_log_init|fini_runtime() which makes relay functions static.
> We have introduced two states "supported" and "enabled". Supported is set
> when we have SSE4.1 support and have relay, GuC log, WC mapping available.
> Enabled is set when support is present and user has requested logging
> through i915_modparams.guc_log_level.
> While at this change, fixed unwind order in intel_uc_fini_misc.

Or, we could rework GuC log a bit.
We could change the meaning of guc_log_level - it would only affect the
"internal" GuC state (verbosity - in other words, the content of buffer used by
GuC). This allows userspace to inspect the content of GuC buffer
(i915_guc_log_dump), but i915 is not copying the data to the relay (we're
ignoring the interrupts recieved from GuC).

This means that we need to introduce alternative way of controling the relay,
let's say another file called "i915_guc_log_relay". Opening this file causes the
relay to be created, we can throw an error if we don't have SSE4.1 there.
(well - the whole runtime is created actually, things are quite badly named
today, runtime means mapping of buffer shared with GuC, relay is the buffer
"shared" with userspace, functions operating on "runtime" should probably setup
both of those rather than just the mapping).

We're also solving the problem of overflows if GuC is loaded with
"guc_log_level > 0" while nobody is consuming the data from the relay.
And we don't really need to handle the "runtime" at module load time at all,
which simplifies things.

I'm working on a series that does all of the above.

-Michał

> 
> Signed-off-by: Sagar Arun Kamble <sagar.a.kamble at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
> Cc: Michal Winiarski <michal.winiarski at intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_guc.c     |  2 +-
>  drivers/gpu/drm/i915/intel_guc_log.c | 97 ++++++++++++++++++++++++++----------
>  drivers/gpu/drm/i915/intel_guc_log.h | 16 +++++-
>  drivers/gpu/drm/i915/intel_uc.c      | 14 ++----
>  4 files changed, 90 insertions(+), 39 deletions(-)