From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sender4-pp-f112.zoho.com (sender4-pp-f112.zoho.com [136.143.188.112]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9B5273D9DDD for ; Mon, 27 Apr 2026 18:28:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.188.112 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777314517; cv=pass; b=TUJtChG4L4H8ERduOoF0N9bjCODkerETCrYOd7GCa/D8UFR7pvbXfeGe2gj5Vi79yOmnUNwBAIVAKjyBcdfCiQUQQ4bzMi21jzEsC3ulyDmlo1s8a6l8tL/y3UsPkLOr2sMFhaS/yZgrzmJyhHAC0Q51w5P8qZhEQgVvPpNYOG4= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777314517; c=relaxed/simple; bh=IzjJG+rAXpFw6bD+ghCY7MJJjWAuBpImbxvIqvId0Rk=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=Jfw+q2J3sI9vCyOyCWHgEC4p+Yrnn90eS/1bIblETXP8aUh1rxMMS+Xu7/Ozmsi/RKLwlhrxgRp2mYob03fZ8astStiK8oJ3Wt/zaqYkpztfhzU0OIgAAqd8fOv1+uCs/2FT9TSisSOHibicDVhPiLEZ/V5cWCUQC1AvT3ov2c4= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (1024-bit key) header.d=collabora.com header.i=nicolas.frattaroli@collabora.com header.b=IdCG6f3E; arc=pass smtp.client-ip=136.143.188.112 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=collabora.com header.i=nicolas.frattaroli@collabora.com header.b="IdCG6f3E" ARC-Seal: i=1; a=rsa-sha256; t=1777314485; cv=none; d=zohomail.com; s=zohoarc; b=FrmMSc0fozgscWvKszWOcrRi2fXjPcWvSQZt4y7Bc/1iiiwYjUx2j8hvm9g5fPGr0vD4al/H4EsFP0NQYbi7TpCP9P0ZuKVeqydw+iT5LlfhJlZznVQC4mF72Bz2qcK88++aUsPHAU7eW4+ij9XL9JP3JQr5sbghi+9Y/UJOAAc= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1777314485; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=MgfLegG7FRAKWEkqVXfJrJQZt2+npwuUV6ms8XivFhk=; b=g5xRx1/U05V4VRYBIMEvE42JbEUc2r2ZwQdaSB0nExyXP1ARy9VBRzBeaOlatQ1PRe6qIImlaOl24JmSGAZ9PhU5Syi7Iw68zrK6VvvFqbhSb9x5u0grogNAKX6qNuyBzEAZCY7huQiu3pjc2nG9d9voTG7H7SOGXKlzRwpug7Y= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=nicolas.frattaroli@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1777314485; s=zohomail; d=collabora.com; i=nicolas.frattaroli@collabora.com; h=From:From:To:To:Cc:Cc:Subject:Subject:Date:Date:Message-ID:In-Reply-To:References:MIME-Version:Content-Transfer-Encoding:Content-Type:Message-Id:Reply-To; bh=MgfLegG7FRAKWEkqVXfJrJQZt2+npwuUV6ms8XivFhk=; b=IdCG6f3EbHuV+iYNYyp2jCDP0SQsdYmPFzg3SDWWFAtedeDdIksPpGmoaXazjA7j fAK/vqLLTBEx7yeEK5/+N5+bUYBJjf7LsUjGmAJkZNg15AaL+WnBW7FR04gjBfPKtP7 CkzblIk/rdHw2FgRt5AlZ1hj3coESB3Cpr4sejBs= Received: by mx.zohomail.com with SMTPS id 1777314483711367.61612657326896; Mon, 27 Apr 2026 11:28:03 -0700 (PDT) From: Nicolas Frattaroli To: Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , dri-devel@lists.freedesktop.org Cc: Christian Hewitt , Diederik de Haas , dri-devel@lists.freedesktop.org, linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org, Jonas Karlman Subject: Re: [PATCH v3 09/13] drm: bridge: dw_hdmi: Use delayed_work to debounce hotplug event Date: Mon, 27 Apr 2026 20:27:58 +0200 Message-ID: In-Reply-To: <20260403185303.80748-10-jonas@kwiboo.se> References: <20260403185303.80748-1-jonas@kwiboo.se> <20260403185303.80748-10-jonas@kwiboo.se> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" On Friday, 3 April 2026 20:52:55 Central European Summer Time Jonas Karlman wrote: > HDMI Specification Version 1.4b chapter 8.5 mentions: > > An HDMI Sink shall not assert high voltage level on its Hot Plug > Detect pin when the E-EDID is not available for reading. > > A Source may use a high voltage level Hot Plug Detect signal to > initiate the reading of E-EDID data. > > An HDMI Sink shall indicate any change to the contents of the E-EDID > by driving a low voltage level pulse on the Hot Plug Detect pin. This > pulse shall be at least 100 msec. > > Use a work queue to debounce reacting on HPD events to better handle a > HPD low voltage level pulse when a sink changes the EDID. > > The 1100 msec hotplug debounce timeout was arbitrarily picked to match > other drivers using same const, and testing using a Raspberry Pi Monitor > seem to use a 200-300 msec pulse when going from standby to power on > state. > > Signed-off-by: Jonas Karlman > --- > v3: New patch > --- > drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 24 +++++++++++++++++++---- > 1 file changed, 20 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c > index f3f8144ae98e..4d079b689b3b 100644 > --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c > +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c > @@ -51,6 +51,8 @@ > > #define HDMI14_MAX_TMDSCLK 340000000 > > +#define HOTPLUG_DEBOUNCE_MS 1100 > + > static const u16 csc_coeff_default[3][4] = { > { 0x2000, 0x0000, 0x0000, 0x0000 }, > { 0x0000, 0x2000, 0x0000, 0x0000 }, > @@ -192,6 +194,7 @@ struct dw_hdmi { > hdmi_codec_plugged_cb plugged_cb; > struct device *codec_dev; > enum drm_connector_status last_connector_result; > + struct delayed_work hpd_work; > }; > > const struct dw_hdmi_plat_data *dw_hdmi_to_plat_data(struct dw_hdmi *hdmi) > @@ -2528,6 +2531,7 @@ static void dw_hdmi_connector_force(struct drm_connector *connector) > > mutex_lock(&hdmi->mutex); > hdmi->force = connector->force; > + hdmi->last_connector_result = connector->status; > dw_hdmi_update_phy_mask(hdmi); > mutex_unlock(&hdmi->mutex); > } > @@ -3046,6 +3050,16 @@ void dw_hdmi_setup_rx_sense(struct dw_hdmi *hdmi, bool hpd, bool rx_sense) > } > EXPORT_SYMBOL_GPL(dw_hdmi_setup_rx_sense); > > +static void dw_hdmi_hpd_work(struct work_struct *work) > +{ > + struct dw_hdmi *hdmi = container_of(work, struct dw_hdmi, hpd_work.work); > + > + if (hdmi->bridge.dev) { > + drm_helper_hpd_irq_event(hdmi->bridge.dev); > + drm_bridge_hpd_notify(&hdmi->bridge, hdmi->last_connector_result); I think you'll want to `mutex_lock(&hdmi->mutex);` (or better yet, `guard(mutex)(&hdmi->mutex)` or `scoped_guard(mutex, &hdmi->mutex) {`) here before reading last_connector_result, otherwise you'll have a data race with any writers. > + } > +} > + > static irqreturn_t dw_hdmi_irq(int irq, void *dev_id) > { > struct dw_hdmi *hdmi = dev_id; > @@ -3097,10 +3111,8 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id) > status == connector_status_connected ? > "plugin" : "plugout"); > > - if (hdmi->bridge.dev) { > - drm_helper_hpd_irq_event(hdmi->bridge.dev); > - drm_bridge_hpd_notify(&hdmi->bridge, status); > - } > + mod_delayed_work(system_percpu_wq, &hdmi->hpd_work, > + msecs_to_jiffies(HOTPLUG_DEBOUNCE_MS)); > } > > hdmi_writeb(hdmi, intr_stat, HDMI_IH_PHY_STAT0); > @@ -3420,6 +3432,8 @@ struct dw_hdmi *dw_hdmi_probe(struct platform_device *pdev, > goto err_res; > } > > + INIT_DELAYED_WORK(&hdmi->hpd_work, dw_hdmi_hpd_work); > + > ret = devm_request_threaded_irq(dev, irq, dw_hdmi_hardirq, > dw_hdmi_irq, IRQF_SHARED, > dev_name(dev), hdmi); > @@ -3552,6 +3566,8 @@ EXPORT_SYMBOL_GPL(dw_hdmi_probe); > > void dw_hdmi_remove(struct dw_hdmi *hdmi) > { > + disable_delayed_work_sync(&hdmi->hpd_work); > + > drm_bridge_remove(&hdmi->bridge); > > if (hdmi->audio && !IS_ERR(hdmi->audio)) > Kind regards, Nicolas Frattaroli