From aafee2eb8ce86c13b3dde819de2f93d0ba61a040 Mon Sep 17 00:00:00 2001 From: Arkadiusz Hiler Date: Tue, 25 Oct 2016 14:48:02 +0200 Subject: [PATCH] drm/i915: fix comment on I915_{READ, WRITE}_FW 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 Cc: Matthew Auld Cc: Mika Kuoppala Signed-off-by: Arkadiusz Hiler Reviewed-by: Matthew Auld Reviewed-by: Chris Wilson [Mika: removed two superfluous lines on comment noted by Chris] Signed-off-by: Mika Kuoppala Link: http://patchwork.freedesktop.org/patch/msgid/1477399682-3133-1-git-send-email-arkadiusz.hiler@intel.com --- drivers/gpu/drm/i915/i915_drv.h | 25 ++++++++++++++++++++++--- 1 file changed, 22 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 7a621c74254e..55afb664b2f8 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -3844,11 +3844,30 @@ __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. on 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. */ #define I915_READ_FW(reg__) __raw_i915_read32(dev_priv, (reg__)) #define I915_WRITE_FW(reg__, val__) __raw_i915_write32(dev_priv, (reg__), (val__)) -- 2.20.1