From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Wilson Subject: Re: [PATCH 2/6] drm/i915: Add a delay in Displayport AUX transactions for compliance testing Date: Wed, 25 Jun 2014 07:45:56 +0100 Message-ID: <20140625064556.GA23572@nuc-i3427.alporthouse.com> References: <1403647974-42377-1-git-send-email-tprevite@gmail.com> <1403647974-42377-3-git-send-email-tprevite@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from fireflyinternet.com (mail.fireflyinternet.com [87.106.93.118]) by gabe.freedesktop.org (Postfix) with ESMTP id 481076E633 for ; Tue, 24 Jun 2014 23:46:00 -0700 (PDT) Content-Disposition: inline In-Reply-To: <1403647974-42377-3-git-send-email-tprevite@gmail.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" To: Todd Previte Cc: intel-gfx@lists.freedesktop.org List-Id: intel-gfx@lists.freedesktop.org On Tue, Jun 24, 2014 at 03:12:50PM -0700, Todd Previte wrote: > Several compliance tests require that follow-up AUX transactions (after a > failure or no response) are not resent sooner than 400us later. Add a 400us > delay to the response time of any failed transaction to account for this. > > Signed-off-by: Todd Previte > --- > drivers/gpu/drm/i915/intel_dp.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c > index 3bd1780..43fcabe 100644 > --- a/drivers/gpu/drm/i915/intel_dp.c > +++ b/drivers/gpu/drm/i915/intel_dp.c > @@ -561,8 +561,12 @@ intel_dp_aux_ch(struct intel_dp *intel_dp, > DP_AUX_CH_CTL_RECEIVE_ERROR); > > if (status & (DP_AUX_CH_CTL_TIME_OUT_ERROR | > - DP_AUX_CH_CTL_RECEIVE_ERROR)) > + DP_AUX_CH_CTL_RECEIVE_ERROR)) { I think "required for DP compliance testing" is a little verbose and can be shortened to "DP requires". If you have a spec reference handy, that would be useful. /* 10.2.1: DP requires 400us delay after an error. */ > + /* 400us delay between transactions for errors/timeouts > + required for DP compliance testing */ > + udelay(400); > continue; > + } > if (status & DP_AUX_CH_CTL_DONE) > break; -- Chris Wilson, Intel Open Source Technology Centre