On Tue, Oct 25, 2016 at 02:48:02PM +0200, Arkadiusz Hiler wrote: > Comment mentioned use of intel_uncore_forcewake_irq{unlock, lock} > functions which are nonexistent (and never were). > > The description was also incomplete and could cause confusion. Updated > comment is more elaborate on usage and caveats. > > v2: mention __locked variant of intel_uncore_forcewake_{get,put} instead > of plain ones > > Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > Cc: Matthew Auld <matthew.auld@xxxxxxxxx> > Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx> > Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@xxxxxxxxx> > --- > drivers/gpu/drm/i915/i915_drv.h | 28 +++++++++++++++++++++++++--- > 1 file changed, 25 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h > index b4cb1f0..e0f3fa4 100644 > --- a/drivers/gpu/drm/i915/i915_drv.h > +++ b/drivers/gpu/drm/i915/i915_drv.h > @@ -3840,11 +3840,33 @@ __raw_write(64, q) > #undef __raw_write > > /* These are untraced mmio-accessors that are only valid to be used inside > - * critical sections inside IRQ handlers where forcewake is explicitly > + * critical sections, such as inside IRQ handlers, where forcewake is explicitly > * controlled. > + * > * Think twice, and think again, before using these. > - * Note: Should only be used between intel_uncore_forcewake_irqlock() and > - * intel_uncore_forcewake_irqunlock(). > + * > + * As an example, these accessors can possibly be used between: > + * > + * spin_lock_irq(&dev_priv->uncore.lock); > + * intel_uncore_forcewake_get__locked(); > + * > + * and > + * > + * intel_uncore_forcewake_put__locked(); > + * spin_unlock_irq(&dev_priv->uncore.lock); > + * > + * > + * Note: some registers may not need forcewake held, so > + * intel_uncore_forcewake_{get,put} can be omitted, see > + * intel_uncore_forcewake_for_reg(). > + * > + * Certain architectures will die if the same cacheline is concurrently accessed > + * by different clients (e.g. Ivybridge). Access to registers should therefore e.g. on Ivybridge > + * generally be serialised, by either the dev_priv->uncore.lock or a more > + * localised lock guarding all access to that bank of registers. > + * > + * Code may be serialised by different lock, so immediate > + * spin_{lock,unlock}_irq() may not be necessary. This last sentence is redundant since the reason why we need some lock somewhere is given above. With that, Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> -Chris -- Chris Wilson, Intel Open Source Technology Centre _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx