The GT MCR code currently relies on uncore->lock to avoid race
conditions on the steering control register during MCR operations. The
*_fw() versions of MCR operations expect the caller to already hold
uncore->lock, while the non-fw variants manage the lock internally.
However the sole callsite of intel_gt_mcr_wait_for_reg_fw() does not
currently obtain the forcewake lock, allowing a potential race condition
(and triggering an assertion on lockdep builds). Furthermore, since
'wait for register value' requests may not return immediately, it is
undesirable to hold a fundamental lock like uncore->lock for the entire
wait and block all other MMIO for the duration; rather the lock is only
needed around the MCR read operations and can be released during the
delays.
Convert intel_gt_mcr_wait_for_reg_fw() to a non-fw variant that will
manage uncore->lock internally. This does have the side effect of
causing an unnecessary lookup in the forcewake table on each read
operation, but since the caller is still holding the relevant forcewake
domain, this will ultimately just incremenent the reference count and
won't actually cause any additional MMIO traffic.
In the future we plan to switch to a dedicated MCR lock to protect the
steering critical section rather than using the overloaded and
high-traffic uncore->lock; on MTL and beyond the new lock can be
implemented on top of the hardware-provided synchonization mechanism for
steering.
Fixes: 3068bec83e ("drm/i915/gt: Add intel_gt_mcr_wait_for_reg_fw()")
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221117173358.1980230-1-matthew.d.roper@intel.com
(cherry picked from commit 192bb40f03)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
MTL's graphics IP (Xe_LPG) once again changes the multicast register
types and steering details. Key changes from past platforms:
* The number of instances of some MCR types (NODE, OAAL2, and GAM) vary
according to the MTL subplatform and cannot be read from fuse
registers. However steering to instance #0 will always provided a
non-terminated value, so we can lump these all into a single
"instance0" table.
* The MCR steering register (and its bitfields) has changed.
Unlike past platforms, we will be explicitly steering all types of MCR
accesses, including those for "SLICE" and "DSS" ranges; we no longer
rely on implicit steering. On previous platforms, various
hardware/firmware agents that needed to access registers typically had
their own steering control registers, allowing them to perform multicast
steering without clobbering the CPU/kernel steering. Starting with MTL,
more of these agents now share a single steering register (0xFD4) and it
is no longer safe for us to assume that the value will remain unchanged
from how we initialized it during startup. There is also a slight
chance of race conditions between the driver and a hardware/firmware
agent, so the hardware provides a semaphore register that can be used to
coordinate access to the steering register. Support for the semaphore
register will be introduced in a future patch.
v2:
- Use Xe_LPG terminology instead of "MTL 3D" since it's the IP version
we're matching on now rather than the platform.
- Don't combine l3bank and mslice masks into a union. It's not related
to the other changes here and we might still need both of them on
some future platform.
- Separate debug dumping of steering settings to a separate helper
function. (Tvrtko)
- Update debug dumping to include DSS ranges (and future-proof it so
that any new ranges added on future platforms will also be dumped).
- Restore MULTICAST bit at the end of rw_with_mcr_steering_fw() if we
cleared it. Also force the MULTICAST bit to true at the beginning of
multicast writes just to be safe. (Bala)
Bspec: 67788, 67112
Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Cc: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221014230239.1023689-14-matthew.d.roper@intel.com
Rather than treating multicast registers as 'i915_reg_t' let's define
them as a completely new type. This will allow the compiler to help us
make sure we're using multicast-aware functions to operate on multicast
registers.
This plan does break down a bit in places where we're just maintaining
heterogeneous lists of registers (e.g., various MMIO whitelists used by
perf, GVT, etc.) rather than performing reads/writes. We only really
care about the offset in those cases, so for now we can "cast" the
registers as non-MCR, leaving us with a list of i915_reg_t's, but we may
want to look for better ways to store mixed collections of i915_reg_t
and i915_mcr_reg_t in the future.
v2:
- Add TLB invalidation registers
v3:
- Make type checking of i915_mmio_reg_offset() stricter. It will
accept either i915_reg_t or i915_mcr_reg_t, but will now raise a
compile error if any other type is passed, even if that type contains
a 'reg' field. (Jani)
- Drop a ton of GVT changes; allowing i915_mmio_reg_offset() to take
either an i915_reg_t or an i915_mcr_reg_t means that the huge lists
of MMIO_D*() macros used in GVT will continue to work without
modification. We need only make changes to structures that have an
explicit i915_reg_t in them now.
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221014230239.1023689-13-matthew.d.roper@intel.com
Xe_HP has some MCR registers that need to be polled for completion of
operations like TLB invalidation. Those registers are in the GAM range,
which rolls up the status from each unit into the 'primary' instance's
value. This makes it useful to have a dedicated 'wait for register'
function that handles this on MCR registers, similar to the
__intel_wait_for_register_fw() function we already have for regular
registers.
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Balasubramani Vivekanandan <balasubramani.vivekanandan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221014230239.1023689-8-matthew.d.roper@intel.com
Although the bspec lists several MMIO ranges as "MSLICE," it turns out
that a subset of these are of a "GAM" subclass that has unique rules and
doesn't followed regular mslice steering behavior.
* Xe_HP SDV: GAM ranges must always be steered to 0,0. These
registers share the regular steering control register (0xFDC) with
other steering types
* DG2: GAM ranges must always be steered to 1,0. GAM registers have a
dedicated steering control register (0xFE0) so we can set the value
once at startup and rely on implicit steering. Technically the
hardware default should already be set to 1,0 properly, but it never
hurts to ensure that in the driver.
Bspec: 66534
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Prathap Kumar Valsan <prathap.kumar.valsan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220916014345.3317739-1-matthew.d.roper@intel.com
Although all DSS belong to a single pool on Xe_HP platforms (i.e.,
they're not organized into slices from a topology point of view), we do
still need to pass 'group' and 'instance' targets when steering register
accesses to a specific instance of a per-DSS multicast register. The
rules for how to determine group and instance IDs (which previously used
legacy terms "slice" and "subslice") varies by platform. Some platforms
determine steering by gslice membership, some platforms by cslice
membership, and future platforms may have other rules.
Since looping over each DSS and performing steered unicast register
accesses is a relatively common pattern, let's add a dedicated iteration
macro to handle this (and replace the platform-specific "instdone" loop
we were using previously. This will avoid the calling code needing to
figure out the details about how to obtain steering IDs for a specific
DSS.
Most of the places where we use this new loop are in the GPU errorstate
code at the moment, but we do have some additional features coming in
the future that will also need to loop over each DSS and steer some
register accesses accordingly.
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Atwood <matthew.s.atwood@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220701232006.1016135-1-matthew.d.roper@intel.com
Let's replace the assortment of intel_gt_* and intel_uncore_* functions
that operate on MCR registers with a cleaner set of interfaces:
* intel_gt_mcr_read -- unicast read from specific instance
* intel_gt_mcr_read_any[_fw] -- unicast read from any non-terminated
instance
* intel_gt_mcr_unicast_write -- unicast write to specific instance
* intel_gt_mcr_multicast_write[_fw] -- multicast write to all instances
We'll also replace the historic "slice" and "subslice" terminology with
"group" and "instance" to match the documentation for more recent
platforms; these days MCR steering applies to more types of replication
than just slice/subslice.
v2:
- Reference the new kerneldoc from i915.rst. (Jani)
- Tweak the wording of the documentation for a couple functions to
clarify the difference between "_fw" and non-"_fw" forms.
v3:
- s/read/write/ to fix copy-paste mistake in a couple comments.
(Harish)
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Acked-by: Jani Nikula <jani.nikula@linux.intel.com>
Reviewed-by: Harish Chegondi <harish.chegondi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220615001019.1821989-3-matthew.d.roper@intel.com
Handling of multicast/replicated registers is spread across intel_gt.c
and intel_uncore.c today. As multicast handling and the related
steering logic gets more complicated with the addition of new platforms
and new rules it makes sense to centralize it all in one place.
For now the existing functions have been moved to the new .c/.h as-is.
Function renames and updates to operate in a more consistent manner will
be done in subsequent patches.
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Acked-by: Jani Nikula <jani.nikula@linux.intel.com>
Reviewed-by: Harish Chegondi <harish.chegondi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220615001019.1821989-2-matthew.d.roper@intel.com
