Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754849AbcLOE1c (ORCPT ); Wed, 14 Dec 2016 23:27:32 -0500 Received: from www.osadl.org ([62.245.132.105]:43731 "EHLO www.osadl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753482AbcLOE1b (ORCPT ); Wed, 14 Dec 2016 23:27:31 -0500 From: Nicholas Mc Guire To: Daniel Vetter Cc: Shashank Sharma , Jani Nikula , David Airlie , intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Nicholas Mc Guire Subject: [PATCH] drm/i915: use udelay for very short delays Date: Thu, 15 Dec 2016 05:29:07 +0100 Message-Id: <1481776147-23041-1-git-send-email-hofrat@osadl.org> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 994 Lines: 31 Even on fast systems a 2 microsecond delay is most likely more efficient as a busy-wait loop. The overhead of a hrtimer does not seem warranted - change this to a udelay(2). Signed-off-by: Nicholas Mc Guire --- Problem found by coccinelle: Patch was compile tested with: x86_64_defconfig (implies CONFIG_DRM_I915) Patch is against 4.9.0 (localversion-next is next-20161214) drivers/gpu/drm/i915/intel_dsi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/intel_dsi.c b/drivers/gpu/drm/i915/intel_dsi.c index 5b72c50..19fe86b 100644 --- a/drivers/gpu/drm/i915/intel_dsi.c +++ b/drivers/gpu/drm/i915/intel_dsi.c @@ -379,7 +379,7 @@ static void bxt_dsi_device_ready(struct intel_encoder *encoder) val &= ~ULPS_STATE_MASK; val |= (ULPS_STATE_ENTER | DEVICE_READY); I915_WRITE(MIPI_DEVICE_READY(port), val); - usleep_range(2, 3); + udelay(2); /* 3. Exit ULPS */ val = I915_READ(MIPI_DEVICE_READY(port)); -- 2.1.4