[PATCH 1/3] drm/i915: Show engine flags in sysfs

[Chris Wilson]

Quoting Tvrtko Ursulin (2020-06-02 16:42:45)
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> Show engine flags together with other per-engine data in sysfs.
> 
> We need this in order to be able to support heterogenous feature sets
> between the engines which are currently not visible from the scheduler
> caps interface.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/sysfs_engines.c | 86 +++++++++++++++++++++----
>  1 file changed, 75 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/sysfs_engines.c b/drivers/gpu/drm/i915/gt/sysfs_engines.c
> index 535cc1169e54..36e0c2fcebef 100644
> --- a/drivers/gpu/drm/i915/gt/sysfs_engines.c
> +++ b/drivers/gpu/drm/i915/gt/sysfs_engines.c
> @@ -48,6 +48,79 @@ inst_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
>  static struct kobj_attribute inst_attr =
>  __ATTR(instance, 0444, inst_show, NULL);
>  
> +static ssize_t repr_trim(char *buf, ssize_t len)
> +{
> +       /* Trim off the trailing space and replace with a newline */
> +       if (len > PAGE_SIZE)
> +               len = PAGE_SIZE;
> +       if (len > 0)
> +               buf[len - 1] = '\n';
> +
> +       return len;
> +}
> +
> +static const char * const engine_flags[] = {
> +       [ilog2(I915_ENGINE_USING_CMD_PARSER)] = "cmdparser",
> +       [ilog2(I915_ENGINE_SUPPORTS_STATS)] = "busy_stats",
> +       [ilog2(I915_ENGINE_HAS_PREEMPTION)] = "preemption",
> +       [ilog2(I915_ENGINE_HAS_SEMAPHORES)] = "semaphores",
> +       [ilog2(I915_ENGINE_HAS_TIMESLICES)] = "timeslicing",
> +       [ilog2(I915_ENGINE_NEEDS_BREADCRUMB_TASKLET)] = "", /* non-abi */
> +       [ilog2(I915_ENGINE_IS_VIRTUAL)] = "", /* non-abi */
> +       [ilog2(I915_ENGINE_HAS_RELATIVE_MMIO)] = "relative_mmio",
> +       [ilog2(I915_ENGINE_REQUIRES_CMD_PARSER)] = "requires_cmdparser",

s/requires_//; to the user they only should know that there is one.

using/requires should be an internal detail. Probably we should make
requires be non-abi and also mark up using-cmd-parser for gen9. (For
reporting simplicity.)

Although we should get around to fleshing out the ability to use
timeslicing effectively from userspace :p

> +};
> +
> +static ssize_t
> +__flags_show(struct intel_engine_cs *engine, unsigned int flags, char *buf,
> +            bool show_unknown)
> +{
> +       const unsigned int count = ARRAY_SIZE(engine_flags);
> +       unsigned int n;
> +       ssize_t len;
> +
> +       BUILD_BUG_ON(!typecheck(typeof(flags), engine->flags));
> +       BUILD_BUG_ON(count > BITS_PER_TYPE(typeof(flags)));
> +
> +       len = 0;
> +       for_each_set_bit(n,
> +                        (unsigned long *)&flags,
> +                        show_unknown ? BITS_PER_TYPE(typeof(flags)) : count) {
> +               if (n >= count || !engine_flags[n]) {
> +                       if (GEM_WARN_ON(show_unknown))
> +                               len += snprintf(buf + len, PAGE_SIZE - len,
> +                                               "[%x] ", n);
> +               } else {
> +                       if (strlen(engine_flags[n]))

Good, you hid the extra spaces.

Heh, I wonder if we should alphabetically sort the strings :)
Just so we don't get into trouble with the order becoming ABI
(constraining the flag values).
-Chris