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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 6E2E3C2BA19 for ; Tue, 21 Apr 2020 07:46:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 52B4A2074B for ; Tue, 21 Apr 2020 07:46:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727100AbgDUHqK (ORCPT ); Tue, 21 Apr 2020 03:46:10 -0400 Received: from hostingweb31-40.netsons.net ([89.40.174.40]:42345 "EHLO hostingweb31-40.netsons.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725992AbgDUHqK (ORCPT ); Tue, 21 Apr 2020 03:46:10 -0400 Received: from [37.160.45.76] (port=22553 helo=[192.168.42.159]) by hostingweb31.netsons.net with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.93) (envelope-from ) id 1jQnbW-008XoL-Sf; Tue, 21 Apr 2020 09:46:03 +0200 Subject: Re: [PATCH v11 2/2] media: v4l: xilinx: Add Xilinx MIPI CSI-2 Rx Subsystem driver To: Laurent Pinchart Cc: Vishal Sagar , Hyun Kwon , mchehab@kernel.org, robh+dt@kernel.org, mark.rutland@arm.com, Michal Simek , linux-media@vger.kernel.org, devicetree@vger.kernel.org, hans.verkuil@cisco.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dinesh Kumar , Sandip Kothari , Jacopo Mondi , Hyun Kwon References: <20200409194424.45555-1-vishal.sagar@xilinx.com> <20200409194424.45555-3-vishal.sagar@xilinx.com> <20200419180222.GB8117@pendragon.ideasonboard.com> <860c27da-eba0-ddcb-719b-52b2725bd9bf@lucaceresoli.net> <20200420195714.GB8195@pendragon.ideasonboard.com> From: Luca Ceresoli Message-ID: <0a3ea86b-cb4c-a1db-664e-cfa555d8ccf8@lucaceresoli.net> Date: Tue, 21 Apr 2020 09:45:56 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200420195714.GB8195@pendragon.ideasonboard.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - hostingweb31.netsons.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - lucaceresoli.net X-Get-Message-Sender-Via: hostingweb31.netsons.net: authenticated_id: luca@lucaceresoli.net X-Authenticated-Sender: hostingweb31.netsons.net: luca@lucaceresoli.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Laurent, On 20/04/20 21:57, Laurent Pinchart wrote: > Hi Luca, > > On Mon, Apr 20, 2020 at 09:24:25PM +0200, Luca Ceresoli wrote: >> On 19/04/20 20:02, Laurent Pinchart wrote: >> [...] >>>> +static irqreturn_t xcsi2rxss_irq_handler(int irq, void *dev_id) >>>> +{ >>>> + struct xcsi2rxss_state *state = (struct xcsi2rxss_state *)dev_id; >>>> + struct xcsi2rxss_core *core = &state->core; >>>> + u32 status; >>>> + >>>> + status = xcsi2rxss_read(core, XCSI_ISR_OFFSET) & XCSI_ISR_ALLINTR_MASK; >>>> + dev_dbg_ratelimited(core->dev, "interrupt status = 0x%08x\n", status); >>> >>> As this is expected to occur for every frame, I would drop the message, >>> even if rate-limited. >>> >>>> + >>>> + if (!status) >>>> + return IRQ_NONE; >>>> + >>>> + /* Received a short packet */ >>>> + if (status & XCSI_ISR_SPFIFONE) { >>>> + dev_dbg_ratelimited(core->dev, "Short packet = 0x%08x\n", >>>> + xcsi2rxss_read(core, XCSI_SPKTR_OFFSET)); >>>> + } >>> >>> Same here, this will occur all the time, I'd remove this message. You >>> need to read XCSI_SPKTR_OFFSET though, and you should do so in a loop >>> until the XCSI_CSR_SPFIFONE in XCSI_CSR_OFFSET is cleared in case >>> multiple short packets are received before the interrupt handler >>> executes. >>> >>> I also wonder if it would make sense to extract the frame number from >>> the FS short packet, and make it available through the subdev API. I >>> think it should be reported through a V4L2_EVENT_FRAME_SYNC event. This >>> can be implemented later. >>> >>>> + >>>> + /* Short packet FIFO overflow */ >>>> + if (status & XCSI_ISR_SPFIFOF) >>>> + dev_dbg_ratelimited(core->dev, "Short packet FIFO overflowed\n"); >>>> + >>>> + /* >>>> + * Stream line buffer full >>>> + * This means there is a backpressure from downstream IP >>>> + */ >>>> + if (status & XCSI_ISR_SLBF) { >>>> + dev_alert_ratelimited(core->dev, "Stream Line Buffer Full!\n"); >>>> + xcsi2rxss_stop_stream(state); >>>> + if (core->rst_gpio) { >>>> + gpiod_set_value(core->rst_gpio, 1); >>>> + /* minimum 40 dphy_clk_200M cycles */ >>>> + ndelay(250); >>>> + gpiod_set_value(core->rst_gpio, 0); >>>> + } >>> >>> I don't think you should stop the core here. xcsi2rxss_stop_stream() >>> calls the source .s_stream(0) operation, which usually involves I2C >>> writes that will sleep. >>> >>> You should instead report an event to userspace (it looks like we have >>> no error event defined in V4L2, one should be added), and rely on the >>> normal stop procedure. >> >> FWIW, since a long time I've been using a modified version of this >> routine, where after a Stream Line Buffer Full condition I just stop and >> restart the csi2rx core and the stream continues after a minimal glitch. >> Other subdev are unaware that anything has happened and keep on streaming. >> >> Not sure this is the correct thing to do, but it's working for me. Also >> I proposed this topic in one of the previous iterations of this patch, >> but the situation was different because the stream on/off was not >> propagated back at that time. > > Thanks for the feedback. How often does this occur in practice ? Quite often indeed in my case, as the MIPI stream comes from a remote sensor via a video serdes chipset, and both the cable and the remote sensor module are subject to heavy EMI. Depending on the setup I observed SLBF happening up to 5~10 times per hour. -- Luca