From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 444A0C433ED for ; Thu, 20 May 2021 20:36:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 291D26105A for ; Thu, 20 May 2021 20:36:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239267AbhETUiF (ORCPT ); Thu, 20 May 2021 16:38:05 -0400 Received: from m43-7.mailgun.net ([69.72.43.7]:11910 "EHLO m43-7.mailgun.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239116AbhETUiF (ORCPT ); Thu, 20 May 2021 16:38:05 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1621543003; h=Message-ID: References: In-Reply-To: Subject: Cc: To: From: Date: Content-Transfer-Encoding: Content-Type: MIME-Version: Sender; bh=8tvSTWWqWbfweM3Qyf/os8ExRoa7DxBNGE9VA9w7u6c=; b=pHSoLPSp8l9wGjxOP8dzsAhR9I64otsZrpdtHIyLmkPJiZ9BGCfF9kHpcaTTNGpeHkMeWGUd wYB60LDMYyb1GRxvJHyAN5Kg+9cQTRbnoVyKrtxcJGOvjGzMwazYBYS/MTbrXYTHA8qkWDrh 1OqMMP0TSWeQLbErf5s9GiCvB1I= X-Mailgun-Sending-Ip: 69.72.43.7 X-Mailgun-Sid: WyI1MzIzYiIsICJsaW51eC1hcm0tbXNtQHZnZXIua2VybmVsLm9yZyIsICJiZTllNGEiXQ== Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n06.prod.us-west-2.postgun.com with SMTP id 60a6c854f752fca66808a126 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Thu, 20 May 2021 20:36:36 GMT Sender: khsieh=codeaurora.org@mg.codeaurora.org Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 4ED84C43460; Thu, 20 May 2021 20:36:36 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: khsieh) by smtp.codeaurora.org (Postfix) with ESMTPSA id 1B7B1C4338A; Thu, 20 May 2021 20:36:35 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 20 May 2021 13:36:35 -0700 From: khsieh@codeaurora.org To: Stephen Boyd Cc: agross@kernel.org, bjorn.andersson@linaro.org, robdclark@gmail.com, sean@poorly.run, vkoul@kernel.org, abhinavk@codeaurora.org, aravindh@codeaurora.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 1/2] drm/msm/dp: handle irq_hpd with sink_count = 0 correctly In-Reply-To: References: <1621013713-6860-1-git-send-email-khsieh@codeaurora.org> Message-ID: <5a6c86f4a5be914102214e45f8afc10c@codeaurora.org> X-Sender: khsieh@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 2021-05-20 12:28, Stephen Boyd wrote: > Quoting khsieh@codeaurora.org (2021-05-20 09:08:03) >> On 2021-05-19 14:06, Stephen Boyd wrote: >> > Quoting khsieh@codeaurora.org (2021-05-19 09:01:02) >> >> On 2021-05-18 14:42, Stephen Boyd wrote: >> >> > Quoting Kuogee Hsieh (2021-05-14 10:35:13) >> >> >> irq_hpd interrupt should be handled after dongle plugged in and >> >> >> before dongle unplugged. Hence irq_hpd interrupt is enabled at >> >> >> the end of the plugin handle and disabled at the beginning of >> >> >> unplugged handle. Current irq_hpd with sink_count = 0 is wrongly >> >> >> handled same as the dongle unplugged which tears down the mainlink >> >> >> and disables the phy. This patch fixes this problem by only tearing >> >> >> down the mainlink but keeping phy enabled at irq_hpd with >> >> >> sink_count = 0 handle so that next irq_hpd with sink_count =1 can be >> >> >> handled by setup mainlink only. >> >> >> >> >> >> Changes in v2: >> >> >> -- add ctrl->phy_Power_count >> >> >> >> >> >> Changes in v3: >> >> >> -- del ctrl->phy_Power_count >> >> >> -- add phy_power_off to dp_ctrl_off_link_stream() >> >> >> >> >> >> Changes in v4: >> >> >> -- return immediately if clock disable failed at >> >> >> dp_ctrl_off_link_stream() >> >> >> >> >> >> Signed-off-by: Kuogee Hsieh >> >> > >> >> > I think we want some Fixes tag. Not sure what it would be though. >> >> > >> >> > I also noticed that if I plug and unplug the HDMI cable from my apple >> >> > dongle that I see this error message >> >> > >> >> > [drm:dp_display_usbpd_attention_cb] *ERROR* Disconnected, no >> >> > DP_LINK_STATUS_UPDATED >> >> >> >> > *ERROR* Disconnected, no DP_LINK_STATUS_UPDATED <== this is caused by >> >> > dongle generate the second >> >> irq_hpd with sink_count = 0 after first first irq_hpd with sink_count >> >> = >> >> 0. The fix is you have >> >> set dongle to D3 (power off) state after first irq_pd with sink_count >> >> =display_disable >> >> 0 handled. >> >> I have a patch fix this problem. I will merge and re submit for >> >> review. >> > >> > That's good. I still don't understand how the kthread can't race with >> > irq_hpd and hpd going low though. Userspace will have to disable >> > thectrl_off_link_stream()). >> > display and that could happen far later than the time that the hpd low >> > interrupt fires and is processed. Can't hpd go high during that time >> > and >> > then blip before userspace notices and disables the display? >> > >> > Put another way, putting the dongle into D3 state may make the race >> > window smaller, but it's not fixing the root cause of the problem which >> > is that the kthread is running later and userspace is involved in the >> > state of the dongle while irqs are firing. The three different contexts >> > have to coordinate work, so it feels like a better approach would be to >> > shut off the irq_hpd interrupt once hpd goes low for an unplug in >> > hardirq context so that we don't have to consider the cable state or >> > userspace changing the state after we notify it. >> >> There is no race condition here. >> The interrupts are converted into event and stored at event q. >> event thread service event sequentially and make sure transaction had >> been completed before service next event. >> The first irq_hpd with sink_count = 0 is handled and this transaction >> will not completed until user space frame work turn off display >> (msm_dp_display_disable()). >> After that, the second irq_hpd with sink_count will be service which >> found that display is off so it spill out DP_LINK_STATUS_UPDATED >> warning >> message and do nothing. >> >> Put dongle to D3 state so that it will not issue the unnecessary >> second >> irq_hpd with sink_count = 0. this will prevent the annoy but unharmful >> DP_LINK_STATUS_UPDATED warning message. >> Again, we can not disable hpd interrupt since dongle still attached >> and >> hdmi cable can be plugged in at any instant. >> > > Right I'm not suggesting to disable hpd interrupt, just the hpd_irq > interrupt once an unplug irq comes in, and do that in hardirq context. > Also, I'm suggesting that we consider unplug as a higher priority if > the > hard irq handler is delayed for some reason and both an unplug irq and > an hpd irq are pending in the hardware when the hard irq handler is > running. Putting the dongle into D3 state won't fix these problems. [drm:dp_display_usbpd_attention_cb] *ERROR* Disconnected, no DP_LINK_STATUS_UPDATED <== you can see this warning message by just unplugged hdmi cable out of dongle (dongle still attached to DUT).