From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (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 88F2C127E3B for ; Mon, 6 May 2024 07:35:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714980943; cv=none; b=eUBMSDHS8LsiXBxTu5BEcSWw/CmoYPxQIv+aLV0w7egQWqDERULD9Bje6Nah5K/cnHcEws8weBQMI551fGFZc5TrzvhFvhawz5GKvx0oyExayrPwq4FOEqACK7gnJMMHdRUw/g/BJLVzKOopLkure04g87W/Zp7kH14ci5PEhKQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714980943; c=relaxed/simple; bh=n5+hynqpfyw2VkPWlAy7ChrItQVLYJ1f8V2xfUMm5QY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GHZ9a6fj+fKLSqhwwIQlXijx93pjvSf8uCMj4PpDO/XXrByA0IX0AZXJDOTiZvr768cnqo6IDJtPns8O5CrjXQJZrnAWX/Y6TtSWhf9FFrQ/vsoTQBiRhbM3TO8WldG3Dzo5jRT9oFujjy3/AspDOHBu8Sjm3dckvMhXUeCms6I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=P93j5mis; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="P93j5mis" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id E680E836; Mon, 6 May 2024 09:35:37 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1714980938; bh=n5+hynqpfyw2VkPWlAy7ChrItQVLYJ1f8V2xfUMm5QY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=P93j5missxNkHoWP51IhSnZa8MCPh3t/vBhIXL35U4+LIY1WxMC85iW/7gPR5ag+q Ei6nFmCIqZu+Z18Sz8zHujvK6+mJlOSjVJ26XDeFa14VDvEGXjX+HsL0F699WeViiD j4NGIH+aSGJDDyQcwg1vYoqYqGLAe6Bh7h6hBJIM= Date: Mon, 6 May 2024 10:35:31 +0300 From: Laurent Pinchart To: Maxime Ripard Cc: Sean Anderson , Tomi Valkeinen , Maarten Lankhorst , Thomas Zimmermann , David Airlie , Daniel Vetter , Michal Simek , dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [BUG] drm: zynqmp_dp: Lockup in zynqmp_dp_bridge_detect when device is unbound Message-ID: <20240506073531.GA10260@pendragon.ideasonboard.com> References: <4d8f4c9b-2efb-4774-9a37-2f257f79b2c9@linux.dev> <20240504122118.GB24548@pendragon.ideasonboard.com> <20240506-charcoal-griffin-of-tact-174dde@houat> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20240506-charcoal-griffin-of-tact-174dde@houat> On Mon, May 06, 2024 at 09:29:36AM +0200, Maxime Ripard wrote: > Hi Laurent, Sean, > > On Sat, May 04, 2024 at 03:21:18PM GMT, Laurent Pinchart wrote: > > On Fri, May 03, 2024 at 05:54:32PM -0400, Sean Anderson wrote: > > > I have discovered a bug in the displayport driver on drm-misc-next. To > > > trigger it, run > > > > > > echo fd4a0000.display > /sys/bus/platform/drivers/zynqmp-dpsub/unbind > > > > > > The system will become unresponsive and (after a bit) splat with a hard > > > LOCKUP. One core will be unresponsive at the first zynqmp_dp_read in > > > zynqmp_dp_bridge_detect. > > > > > > I believe the issue is due the registers being unmapped and the block > > > put into reset in zynqmp_dp_remove instead of zynqmp_dpsub_release. > > > > That is on purpose. Drivers are not allowed to access the device at all > > after .remove() returns. > > It's not "on purpose" no. Drivers indeed are not allowed to access the > device after remove, but the kernel shouldn't crash. This is exactly > why we have drm_dev_enter / drm_dev_exit. I didn't mean the crash was on purpose :-) It's the registers being unmapped that is, as nothing should touch those registers after .remove() returns. -- Regards, Laurent Pinchart