@@ -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
+ * 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.
*/
#define I915_READ_FW(reg__) __raw_i915_read32(dev_priv, (reg__))
#define I915_WRITE_FW(reg__, val__) __raw_i915_write32(dev_priv, (reg__), (val__))
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@chris-wilson.co.uk> Cc: Matthew Auld <matthew.auld@intel.com> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com> Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com> --- drivers/gpu/drm/i915/i915_drv.h | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-)