Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754780Ab3JUJMo (ORCPT ); Mon, 21 Oct 2013 05:12:44 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:39633 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753910Ab3JUIvs (ORCPT ); Mon, 21 Oct 2013 04:51:48 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Nicolas Suzor" , "Jani Nikula" , "Todd Previte" , "Daniel Vetter" Date: Mon, 21 Oct 2013 09:46:28 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 085/149] drm/i915/dp: increase i2c-over-aux retry interval on AUX DEFER In-Reply-To: X-SA-Exim-Connect-IP: 212.20.242.100 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1872 Lines: 51 3.2.52-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Jani Nikula commit 8d16f258217f2f583af1fd57c5144aa4bbe73e48 upstream. There is no clear cut rules or specs for the retry interval, as there are many factors that affect overall response time. Increase the interval, and even more so on branch devices which may have limited i2c bit rates. Signed-off-by: Jani Nikula Reference: https://bugs.freedesktop.org/show_bug.cgi?id=60263 Tested-by: Nicolas Suzor Reviewed-by: Todd Previte Signed-off-by: Daniel Vetter Signed-off-by: Ben Hutchings --- drivers/gpu/drm/i915/intel_dp.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -621,7 +621,18 @@ intel_dp_i2c_aux_ch(struct i2c_adapter * DRM_DEBUG_KMS("aux_ch native nack\n"); return -EREMOTEIO; case AUX_NATIVE_REPLY_DEFER: - udelay(100); + /* + * For now, just give more slack to branch devices. We + * could check the DPCD for I2C bit rate capabilities, + * and if available, adjust the interval. We could also + * be more careful with DP-to-Legacy adapters where a + * long legacy cable may force very low I2C bit rates. + */ + if (intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] & + DP_DWN_STRM_PORT_PRESENT) + usleep_range(500, 600); + else + usleep_range(300, 400); continue; default: DRM_ERROR("aux_ch invalid native reply 0x%02x\n", -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/