Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754238Ab3JCEFs (ORCPT ); Thu, 3 Oct 2013 00:05:48 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:46720 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753469Ab3JCEFr (ORCPT ); Thu, 3 Oct 2013 00:05:47 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jani Nikula , Nicolas Suzor , Todd Previte , Daniel Vetter Subject: [ 09/13] drm/i915/dp: increase i2c-over-aux retry interval on AUX DEFER Date: Wed, 2 Oct 2013 21:04:34 -0700 Message-Id: <20131003040401.399706221@linuxfoundation.org> X-Mailer: git-send-email 1.8.4.6.g82e253f.dirty In-Reply-To: <20131003040400.753642257@linuxfoundation.org> References: <20131003040400.753642257@linuxfoundation.org> User-Agent: quilt/0.60-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1888 Lines: 53 3.0-stable 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: Greg Kroah-Hartman --- 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 @@ -531,7 +531,18 @@ 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/