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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 13A87C54E68 for ; Thu, 21 Mar 2024 15:52:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=epGcZw65nFNB2jIc9Iw0OGcKM0yL6/LW5BeWhdM77Yc=; b=jl3fGA2Ja+7Y2B asRuZYuZKfHGnv/5T8+vLJLJuFmsflH9pARvzICLmQA32Gc39vIQZoyBacIo6zf/a48cB7HgyYhqb YUEt4OZOugbSENsMez8L3mrR26FTwfNr03UaAbxY7j2QwK9bcE4MBE4kY9o1kUmDxOSAJcbhcRb5g sMGz36CuidcB9QtzhhYqm9rnHvZgwZzNEOPJuE4pIBBJIzmLuwYgl3c8N2iZqqgjI0rcMBESi3H5M 4H+joplZJQ4ls9vVUt7M5mWRX/ATujBkqw7WS0m55iIEHxt8tCVgpYfKK4ZzB7/EkU37A+Db6j8+0 Q5uLhfirgPX8Tl2auRRg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rnKiY-00000003dKQ-48Or; Thu, 21 Mar 2024 15:52:34 +0000 Received: from out-171.mta0.migadu.com ([91.218.175.171]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rnKiV-00000003dIp-1Vq3 for linux-arm-kernel@lists.infradead.org; Thu, 21 Mar 2024 15:52:32 +0000 Message-ID: <53b2df23-d5ea-498b-a501-b64f753c0074@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1711036347; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=2reTOytJMh5foizD5SWaFSRwZSD2WulrWEB+iTZT+JA=; b=NOYQ4dW4Jm1mvANK62WuzMcS2fhb/Cz2mmzJ6a6obOy1x/zCVi9iJrokRVLaSp8ymgicJ1 O6pMTLiEF44xOjsTQyjS+MmwWPUCZNd03HfTM5NOEg2IrOMCX1fxtfG4WlkkRLr97b3OSz rk28k0t9IEvkCpxUQqE2T71VIEfM5Ro= Date: Thu, 21 Mar 2024 11:52:23 -0400 MIME-Version: 1.0 Subject: Re: [PATCH v2 5/8] drm: zynqmp_dp: Don't retrain the link in our IRQ Content-Language: en-US To: Tomi Valkeinen Cc: Michal Simek , David Airlie , linux-kernel@vger.kernel.org, Daniel Vetter , linux-arm-kernel@lists.infradead.org, Laurent Pinchart , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , dri-devel@lists.freedesktop.org References: <20240319225122.3048400-1-sean.anderson@linux.dev> <20240319225122.3048400-6-sean.anderson@linux.dev> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Sean Anderson In-Reply-To: X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240321_085231_589005_F808D015 X-CRM114-Status: GOOD ( 26.48 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 3/20/24 02:53, Tomi Valkeinen wrote: > On 20/03/2024 00:51, Sean Anderson wrote: >> Retraining the link can take a while, and might involve waiting for >> DPCD reads/writes to complete. This is inappropriate for an IRQ handler. >> Just schedule this work for later completion. This is racy, but will be >> fixed in the next commit. > > You should add the locks first, and use them here, rather than first > adding a buggy commit and fixing it in the next one. I didn't think I could add the locks first since I only noticed the IRQ was threaded right before sending out this series. So yeah, we could add locking, add the workqueue, and then unthread the IRQ. >> Signed-off-by: Sean Anderson >> --- >> Actually, on second look this IRQ is threaded. So why do we have a >> workqueue for HPD events? Maybe we should make it unthreaded? > > Indeed, there's not much work being done in the IRQ handler. I don't know why it's threaded. > > We could move the queued work to be inside the threaded irq handler, > but with a quick look, the HPD work has lines like "msleep(100)" (and > that's inside a for loop...), which is probably not a good thing to do > even in threaded irq handler. > > Although I'm not sure if that code is good to have anywhere. Why do we > even have such code in the HPD work path... We already got the HPD > interrupt. What does "It takes some delay (ex, 100 ~ 500 msec) to get > the HPD signal with some monitors" even mean... The documentation for this bit is | HPD_STATE 0 ro 0x0 Contains the raw state of the HPD pin on the DisplayPort connector. So I think the idea is to perform some debouncing. > Would it be possible to clean up the work funcs a bit (I haven't > looked a the new work func yet), to remove the worst extra sleeps, and > just do all that inside the threaded irq handler? Probably not, since a HPD IRQ results in link retraining, which can take a while. > Do we need to handle interrupts while either delayed work is being done? Probably not. > If we do need a delayed work, would just one work be enough which > handles both HPD_EVENT and HPD_IRQ, instead of two? Maybe, but then we need to determine which pending events we need to handle. I think since we have only two events it will be easier to just have separate workqueues. --Sean _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel