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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 459F5C433F5 for ; Thu, 25 Nov 2021 10:55:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354765AbhKYK6j (ORCPT ); Thu, 25 Nov 2021 05:58:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39410 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349902AbhKYK4a (ORCPT ); Thu, 25 Nov 2021 05:56:30 -0500 Received: from mail-pf1-x42a.google.com (mail-pf1-x42a.google.com [IPv6:2607:f8b0:4864:20::42a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 94CB3C061574 for ; Thu, 25 Nov 2021 02:53:19 -0800 (PST) Received: by mail-pf1-x42a.google.com with SMTP id n26so5585606pff.3 for ; Thu, 25 Nov 2021 02:53:19 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=QkMPxmAisMCF3ygQYjaS2QJ75hZFBa9HFWNDJ/QnYRs=; b=zlmcPERMkC2AQ5nPWSTNMo/YgTg2paNTBy/rQoNkAf5bzuva+amAS6DH8nE8hWZeAg o61zB/G7byBsyO5H4fEqzcw769gSOzqIjE79Pv+fxa6lLXoupcPWnzfp3bKrpvJ6rJbL 8iLcF3ACmaV1KoXcGyk0bE0+dVpDZaAT1wZPRkobgDCUa+erlUCwgRRU1y//hpp4aMjy QwQPxa5iBMaqvRF1fvUQ8P4L+j2CFnoNxLXkPZmBXmwOKUVli1y9/twYrI44vsjzcTeO tSyF7B+mDHzJO8hgCnF6v6w5HbWUib3BDSjZlHgRU2prUPaggaf8AJuhjPRs0aEXuncF htVQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=QkMPxmAisMCF3ygQYjaS2QJ75hZFBa9HFWNDJ/QnYRs=; b=IEYqVLvbTe+FzhFmn54Ie4We3I7lzM9jqnLUpoXg+B75HXWLHRuxkEgyHk0UpAXB3f bIemxyHXDGWyhZrXvgskTP33nFmdC3PZS4kmNWsqiKDS1XIQ6b3qRTw865CgwKDoVc+9 qgZ9rHzaPF3i/UOPOEYK3bXSVz7vxJY+P+rW0+SFtGwq+BpeRj+2kyCAsGkaxcpz/iws EKnrYstFjykoahtIAbNpnbNN4hd+BqYkz9VDUCqHLZUpBTdzCXqRmm2kBR8DY5bwwhEP okXG/Ewcu8YEQlNxkx4DUp71aFIncj8pnXYMKPgLI48FuGRMXlpAQskGMRtlHAcujyAf LZ5g== X-Gm-Message-State: AOAM533+1DxFBb+bzUJ/IC40cGhMwBaM+tTsjIlV6YiJxEDGRGFugOzk fvlc34SfTtkzARYA2/g9kOhSfSbxHT0VmW5fIMbhPA== X-Google-Smtp-Source: ABdhPJzxJLhA52Wd/4I2Ik7v1oHBDf/+mcSCPPPsuZwrUe1OnBu+6VSytqZpCE24fH0MkRNXBrlZ1FbqZq+K9HBtlJY= X-Received: by 2002:a63:85c3:: with SMTP id u186mr10413064pgd.201.1637837598886; Thu, 25 Nov 2021 02:53:18 -0800 (PST) MIME-Version: 1.0 References: <20211116122831.278576-1-martyn.welch@collabora.com> <67e1ba141c570dbbe48945257954f25c8ff2c2ca.camel@collabora.com> In-Reply-To: <67e1ba141c570dbbe48945257954f25c8ff2c2ca.camel@collabora.com> From: Robert Foss Date: Thu, 25 Nov 2021 11:53:04 +0100 Message-ID: Subject: Re: [PATCH] drm/bridge: megachips: Ensure both bridges are probed before registration To: Martyn Welch Cc: dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com, Peter Senna Tschudin , Martin Donnelly , Andrzej Hajda , Neil Armstrong , Laurent Pinchart , Jonas Karlman , Jernej Skrabec Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 24 Nov 2021 at 19:40, Martyn Welch wrote: > > On Tue, 2021-11-23 at 16:18 +0100, Robert Foss wrote: > > Hey Martyn, > > > > On Tue, 16 Nov 2021 at 13:28, Martyn Welch > > wrote: > > > > > > In the configuration used by the b850v3, the STDP2690 is used to read > > > EDID > > > data whilst it's the STDP4028 which can detect when monitors are > > > connected. > > > > > > This can result in problems at boot with monitors connected when the > > > STDP4028 is probed first, a monitor is detected and an attempt is > > > made to > > > read the EDID data before the STDP2690 has probed: > > > > > > [ 3.795721] Unable to handle kernel NULL pointer dereference at > > > virtual address 00000018 > > > [ 3.803845] pgd = (ptrval) > > > [ 3.806581] [00000018] *pgd=00000000 > > > [ 3.810180] Internal error: Oops: 5 [#1] SMP ARM > > > [ 3.814813] Modules linked in: > > > [ 3.817879] CPU: 0 PID: 64 Comm: kworker/u4:1 Not tainted 5.15.0 > > > #1 > > > [ 3.824161] Hardware name: Freescale i.MX6 Quad/DualLite (Device > > > Tree) > > > [ 3.830705] Workqueue: events_unbound deferred_probe_work_func > > > [ 3.836565] PC is at stdp2690_get_edid+0x44/0x19c > > > [ 3.841286] LR is at ge_b850v3_lvds_get_modes+0x2c/0x5c > > > [ 3.846526] pc : [<805eae10>] lr : [<805eb138>] psr: > > > 80000013 > > > [ 3.852802] sp : 81c359d0 ip : 7dbb550b fp : 81c35a1c > > > [ 3.858037] r10: 81c73840 r9 : 81c73894 r8 : 816d9800 > > > [ 3.863270] r7 : 00000000 r6 : 81c34000 r5 : 00000000 r4 : > > > 810c35f0 > > > [ 3.869808] r3 : 80e3e294 r2 : 00000080 r1 : 00000cc0 r0 : > > > 81401180 > > > [ 3.876349] Flags: Nzcv IRQs on FIQs on Mode SVC_32 ISA ARM > > > Segment none > > > [ 3.883499] Control: 10c5387d Table: 1000404a DAC: 00000051 > > > [ 3.889254] Register r0 information: slab kmem_cache start > > > 81401180 pointer offset 0 > > > [ 3.897034] Register r1 information: non-paged memory > > > [ 3.902097] Register r2 information: non-paged memory > > > [ 3.907160] Register r3 information: non-slab/vmalloc memory > > > [ 3.912832] Register r4 information: non-slab/vmalloc memory > > > [ 3.918503] Register r5 information: NULL pointer > > > [ 3.923217] Register r6 information: non-slab/vmalloc memory > > > [ 3.928887] Register r7 information: NULL pointer > > > [ 3.933601] Register r8 information: slab kmalloc-1k start > > > 816d9800 pointer offset 0 size 1024 > > > [ 3.942244] Register r9 information: slab kmalloc-2k start > > > 81c73800 pointer offset 148 size 2048 > > > [ 3.951058] Register r10 information: slab kmalloc-2k start > > > 81c73800 pointer offset 64 size 2048 > > > [ 3.959873] Register r11 information: non-slab/vmalloc memory > > > [ 3.965632] Register r12 information: non-paged memory > > > [ 3.970781] Process kworker/u4:1 (pid: 64, stack limit = > > > 0x(ptrval)) > > > [ 3.977148] Stack: (0x81c359d0 to 0x81c36000) > > > [ 3.981517] 59c0: 80b2b668 > > > 80b2b5bc 000002e2 0000034e > > > [ 3.989712] 59e0: 81c35a8c 816d98e8 81c35a14 7dbb550b 805bfcd0 > > > 810c35f0 81c73840 824addc0 > > > [ 3.997906] 5a00: 00001000 816d9800 81c73894 81c73840 81c35a34 > > > 81c35a20 805eb138 805eadd8 > > > [ 4.006099] 5a20: 810c35f0 00000045 81c35adc 81c35a38 80594188 > > > 805eb118 80d7c788 80dd1848 > > > [ 4.014292] 5a40: 00000000 81c35a50 80dca950 811194d3 80dca7c4 > > > 80dca944 80dca91c 816d9800 > > > [ 4.022485] 5a60: 81c34000 81c760a8 816d9800 80c58c98 810c35f0 > > > 816d98e8 00001000 00001000 > > > [ 4.030678] 5a80: 00000000 00000000 8017712c 81c60000 00000002 > > > 00000001 00000000 00000000 > > > [ 4.038870] 5aa0: 816d9900 816d9900 00000000 7dbb550b 805c700c > > > 00000008 826282c8 826282c8 > > > [ 4.047062] 5ac0: 00001000 81e1ce40 00001000 00000002 81c35bf4 > > > 81c35ae0 805d9694 80593fc0 > > > [ 4.055255] 5ae0: 8017a970 80179ad8 00000179 00000000 81c35bcc > > > 81c35b00 80177108 8017a950 > > > [ 4.063447] 5b00: 00000000 81c35b10 81c34000 00000000 81004fd8 > > > 81010a38 00000000 00000059 > > > [ 4.071639] 5b20: 816d98d4 81fbb718 00000013 826282c8 8017a940 > > > 81c35b40 81134448 00000400 > > > [ 4.079831] 5b40: 00000178 00000000 e063b9c1 00000000 c2000049 > > > 00000040 00000000 00000008 > > > [ 4.088024] 5b60: 82628300 82628380 00000000 00000000 81c34000 > > > 00000000 81fbb700 82628340 > > > [ 4.096216] 5b80: 826283c0 00001000 00000000 00000010 816d9800 > > > 826282c0 801766f8 00000000 > > > [ 4.104408] 5ba0: 00000000 81004fd8 00000049 00000000 00000000 > > > 00000001 80dcf940 80178de4 > > > [ 4.112601] 5bc0: 81c35c0c 7dbb550b 80178de4 81fbb700 00000010 > > > 00000010 810c35f4 81e1ce40 > > > [ 4.120793] 5be0: 81c40908 0000000c 81c35c64 81c35bf8 805a7f18 > > > 805d94a0 81c35c3c 816d9800 > > > [ 4.128985] 5c00: 00000010 81c34000 81c35c2c 81c35c18 8012fce0 > > > 805be90c 81c35c3c 81c35c28 > > > [ 4.137178] 5c20: 805be90c 80173210 81fbb600 81fbb6b4 81c35c5c > > > 7dbb550b 81c35c64 81fbb700 > > > [ 4.145370] 5c40: 816d9800 00000010 810c35f4 81e1ce40 81c40908 > > > 0000000c 81c35c84 81c35c68 > > > [ 4.153565] 5c60: 805a8c78 805a7ed0 816d9800 81fbb700 00000010 > > > 00000000 81c35cac 81c35c88 > > > [ 4.161758] 5c80: 805a8dc4 805a8b68 816d9800 00000000 816d9800 > > > 00000000 8179f810 810c42d0 > > > [ 4.169950] 5ca0: 81c35ccc 81c35cb0 805e47b0 805a8d18 824aa240 > > > 81e1ea80 81c40908 81126b60 > > > [ 4.178144] 5cc0: 81c35d14 81c35cd0 8060db1c 805e46cc 81c35d14 > > > 81c35ce0 80dd90f8 810c4d58 > > > [ 4.186338] 5ce0: 80dd90dc 81fe9740 fffffffe 81fe9740 81e1ea80 > > > 00000000 810c4d6c 80c4b95c > > > [ 4.194531] 5d00: 80dd9a3c 815c6810 81c35d34 81c35d18 8060dc9c > > > 8060d8fc 8246b440 815c6800 > > > [ 4.202724] 5d20: 815c6810 eefd8e00 81c35d44 81c35d38 8060dd80 > > > 8060dbec 81c35d6c 81c35d48 > > > [ 4.210918] 5d40: 805e98a4 8060dd70 00000000 815c6810 810c45b0 > > > 81126e90 81126e90 80dd9a3c > > > [ 4.219112] 5d60: 81c35d8c 81c35d70 80619574 805e9808 815c6810 > > > 00000000 810c45b0 81126e90 > > > [ 4.227305] 5d80: 81c35db4 81c35d90 806168dc 80619514 80625df0 > > > 80623c80 815c6810 810c45b0 > > > [ 4.235498] 5da0: 81c35e6c 815c6810 81c35dec 81c35db8 80616d04 > > > 80616800 81c35de4 81c35dc8 > > > [ 4.243691] 5dc0: 808382b0 80b2f444 8116e310 8116e314 81c35e6c > > > 815c6810 00000003 80dd9a3c > > > [ 4.251884] 5de0: 81c35e14 81c35df0 80616ec8 80616c60 00000001 > > > 810c45b0 81c35e6c 815c6810 > > > [ 4.260076] 5e00: 00000001 80dd9a3c 81c35e34 81c35e18 80617338 > > > 80616e90 00000000 81c35e6c > > > [ 4.268269] 5e20: 80617284 81c34000 81c35e64 81c35e38 80614730 > > > 80617290 81c35e64 8171a06c > > > [ 4.276461] 5e40: 81e220b8 7dbb550b 815c6810 81c34000 815c6854 > > > 81126e90 81c35e9c 81c35e68 > > > [ 4.284654] 5e60: 8061673c 806146a8 8060f5e0 815c6810 00000001 > > > 7dbb550b 00000000 810c5080 > > > [ 4.292847] 5e80: 810c5320 815c6810 81126e90 00000000 81c35eac > > > 81c35ea0 80617554 80616650 > > > [ 4.301040] 5ea0: 81c35ecc 81c35eb0 80615694 80617544 810c5080 > > > 810c5080 810c5094 81126e90 > > > [ 4.309233] 5ec0: 81c35efc 81c35ed0 80615c6c 8061560c 80615bc0 > > > 810c50c0 817eeb00 81412800 > > > [ 4.317425] 5ee0: 814c3000 00000000 814c300d 81119a60 81c35f3c > > > 81c35f00 80141488 80615bcc > > > [ 4.325618] 5f00: 81c60000 81c34000 81c35f24 81c35f18 80143078 > > > 817eeb00 81412800 817eeb18 > > > [ 4.333811] 5f20: 81412818 81003d00 00000088 81412800 81c35f74 > > > 81c35f40 80141a48 80141298 > > > [ 4.342005] 5f40: 81c35f74 81c34000 801481ac 817efa40 817efc00 > > > 801417d8 817eeb00 00000000 > > > [ 4.350199] 5f60: 815a7e7c 81c34000 81c35fac 81c35f78 80149b1c > > > 801417e4 817efc20 817efc20 > > > [ 4.358391] 5f80: ffffe000 817efa40 801499a8 00000000 00000000 > > > 00000000 00000000 00000000 > > > [ 4.366583] 5fa0: 00000000 81c35fb0 80100130 801499b4 00000000 > > > 00000000 00000000 00000000 > > > [ 4.374774] 5fc0: 00000000 00000000 00000000 00000000 00000000 > > > 00000000 00000000 00000000 > > > [ 4.382966] 5fe0: 00000000 00000000 00000000 00000000 00000013 > > > 00000000 00000000 00000000 > > > [ 4.391155] Backtrace: > > > [ 4.393613] [<805eadcc>] (stdp2690_get_edid) from [<805eb138>] > > > (ge_b850v3_lvds_get_modes+0x2c/0x5c) > > > [ 4.402691] r10:81c73840 r9:81c73894 r8:816d9800 r7:00001000 > > > r6:824addc0 r5:81c73840 > > > [ 4.410534] r4:810c35f0 > > > [ 4.413073] [<805eb10c>] (ge_b850v3_lvds_get_modes) from > > > [<80594188>] (drm_helper_probe_single_connector_modes+0x1d4/0x84c) > > > [ 4.424240] r5:00000045 r4:810c35f0 > > > [ 4.427822] [<80593fb4>] (drm_helper_probe_single_connector_modes) > > > from [<805d9694>] (drm_client_modeset_probe+0x200/0x1384) > > > [ 4.439074] r10:00000002 r9:00001000 r8:81e1ce40 r7:00001000 > > > r6:826282c8 r5:826282c8 > > > [ 4.446917] r4:00000008 > > > [ 4.449455] [<805d9494>] (drm_client_modeset_probe) from > > > [<805a7f18>] (__drm_fb_helper_initial_config_and_unlock+0x54/0x5b4) > > > [ 4.460713] r10:0000000c r9:81c40908 r8:81e1ce40 r7:810c35f4 > > > r6:00000010 r5:00000010 > > > [ 4.468556] r4:81fbb700 > > > [ 4.471095] [<805a7ec4>] > > > (__drm_fb_helper_initial_config_and_unlock) from [<805a8c78>] > > > (drm_fbdev_client_hotplug+0x11c/0x1b0) > > > [ 4.482434] r10:0000000c r9:81c40908 r8:81e1ce40 r7:810c35f4 > > > r6:00000010 r5:816d9800 > > > [ 4.490276] r4:81fbb700 > > > [ 4.492814] [<805a8b5c>] (drm_fbdev_client_hotplug) from > > > [<805a8dc4>] (drm_fbdev_generic_setup+0xb8/0x1a4) > > > [ 4.502494] r7:00000000 r6:00000010 r5:81fbb700 r4:816d9800 > > > [ 4.508160] [<805a8d0c>] (drm_fbdev_generic_setup) from > > > [<805e47b0>] (imx_drm_bind+0xf0/0x130) > > > [ 4.516805] r7:810c42d0 r6:8179f810 r5:00000000 r4:816d9800 > > > [ 4.522474] [<805e46c0>] (imx_drm_bind) from [<8060db1c>] > > > (try_to_bring_up_master+0x22c/0x2f0) > > > [ 4.531116] r7:81126b60 r6:81c40908 r5:81e1ea80 r4:824aa240 > > > [ 4.536783] [<8060d8f0>] (try_to_bring_up_master) from > > > [<8060dc9c>] (__component_add+0xbc/0x184) > > > [ 4.545597] r10:815c6810 r9:80dd9a3c r8:80c4b95c r7:810c4d6c > > > r6:00000000 r5:81e1ea80 > > > [ 4.553440] r4:81fe9740 > > > [ 4.555980] [<8060dbe0>] (__component_add) from [<8060dd80>] > > > (component_add+0x1c/0x20) > > > [ 4.563921] r7:eefd8e00 r6:815c6810 r5:815c6800 r4:8246b440 > > > [ 4.569589] [<8060dd64>] (component_add) from [<805e98a4>] > > > (dw_hdmi_imx_probe+0xa8/0xe8) > > > [ 4.577702] [<805e97fc>] (dw_hdmi_imx_probe) from [<80619574>] > > > (platform_probe+0x6c/0xc8) > > > [ 4.585908] r9:80dd9a3c r8:81126e90 r7:81126e90 r6:810c45b0 > > > r5:815c6810 r4:00000000 > > > [ 4.593662] [<80619508>] (platform_probe) from [<806168dc>] > > > (really_probe+0xe8/0x460) > > > [ 4.601524] r7:81126e90 r6:810c45b0 r5:00000000 r4:815c6810 > > > [ 4.607191] [<806167f4>] (really_probe) from [<80616d04>] > > > (__driver_probe_device+0xb0/0x230) > > > [ 4.615658] r7:815c6810 r6:81c35e6c r5:810c45b0 r4:815c6810 > > > [ 4.621326] [<80616c54>] (__driver_probe_device) from [<80616ec8>] > > > (driver_probe_device+0x44/0xe0) > > > [ 4.630313] r9:80dd9a3c r8:00000003 r7:815c6810 r6:81c35e6c > > > r5:8116e314 r4:8116e310 > > > [ 4.638068] [<80616e84>] (driver_probe_device) from [<80617338>] > > > (__device_attach_driver+0xb4/0x12c) > > > [ 4.647227] r9:80dd9a3c r8:00000001 r7:815c6810 r6:81c35e6c > > > r5:810c45b0 r4:00000001 > > > [ 4.654981] [<80617284>] (__device_attach_driver) from > > > [<80614730>] (bus_for_each_drv+0x94/0xd8) > > > [ 4.663794] r7:81c34000 r6:80617284 r5:81c35e6c r4:00000000 > > > [ 4.669461] [<8061469c>] (bus_for_each_drv) from [<8061673c>] > > > (__device_attach+0xf8/0x190) > > > [ 4.677753] r7:81126e90 r6:815c6854 r5:81c34000 r4:815c6810 > > > [ 4.683419] [<80616644>] (__device_attach) from [<80617554>] > > > (device_initial_probe+0x1c/0x20) > > > [ 4.691971] r8:00000000 r7:81126e90 r6:815c6810 r5:810c5320 > > > r4:810c5080 > > > [ 4.698681] [<80617538>] (device_initial_probe) from [<80615694>] > > > (bus_probe_device+0x94/0x9c) > > > [ 4.707318] [<80615600>] (bus_probe_device) from [<80615c6c>] > > > (deferred_probe_work_func+0xac/0xf0) > > > [ 4.716305] r7:81126e90 r6:810c5094 r5:810c5080 r4:810c5080 > > > [ 4.721973] [<80615bc0>] (deferred_probe_work_func) from > > > [<80141488>] (process_one_work+0x1fc/0x54c) > > > [ 4.731139] r10:81119a60 r9:814c300d r8:00000000 r7:814c3000 > > > r6:81412800 r5:817eeb00 > > > [ 4.738981] r4:810c50c0 r3:80615bc0 > > > [ 4.742563] [<8014128c>] (process_one_work) from [<80141a48>] > > > (worker_thread+0x270/0x570) > > > [ 4.750765] r10:81412800 r9:00000088 r8:81003d00 r7:81412818 > > > r6:817eeb18 r5:81412800 > > > [ 4.758608] r4:817eeb00 > > > [ 4.761147] [<801417d8>] (worker_thread) from [<80149b1c>] > > > (kthread+0x174/0x190) > > > [ 4.768574] r10:81c34000 r9:815a7e7c r8:00000000 r7:817eeb00 > > > r6:801417d8 r5:817efc00 > > > [ 4.776417] r4:817efa40 > > > [ 4.778955] [<801499a8>] (kthread) from [<80100130>] > > > (ret_from_fork+0x14/0x24) > > > [ 4.786201] Exception stack(0x81c35fb0 to 0x81c35ff8) > > > [ 4.791266] 5fa0: 00000000 > > > 00000000 00000000 00000000 > > > [ 4.799459] 5fc0: 00000000 00000000 00000000 00000000 00000000 > > > 00000000 00000000 00000000 > > > [ 4.807651] 5fe0: 00000000 00000000 00000000 00000000 00000013 > > > 00000000 > > > [ 4.814279] r10:00000000 r9:00000000 r8:00000000 r7:00000000 > > > r6:00000000 r5:801499a8 > > > [ 4.822120] r4:817efa40 > > > [ 4.824664] Code: e3a02080 e593001c e3a01d33 e3a05000 (e5979018) > > > > > > Split the registration from the STDP4028 probe routine and only > > > perform > > > registration once both the STDP4028 and STDP2690 have probed. > > > > > > Signed-off-by: Martyn Welch > > > CC: Peter Senna Tschudin > > > CC: Martin Donnelly > > > CC: Martyn Welch > > > CC: Andrzej Hajda > > > CC: Neil Armstrong > > > CC: Robert Foss > > > CC: Laurent Pinchart > > > CC: Jonas Karlman > > > CC: Jernej Skrabec > > > --- > > > .../bridge/megachips-stdpxxxx-ge-b850v3-fw.c | 40 +++++++++++++---- > > > -- > > > 1 file changed, 28 insertions(+), 12 deletions(-) > > > > > > diff --git a/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c > > > b/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c > > > index d2808c4a6fb1..72f134849822 100644 > > > --- a/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c > > > +++ b/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c > > > @@ -306,19 +306,10 @@ static void ge_b850v3_lvds_remove(void) > > > mutex_unlock(&ge_b850v3_lvds_dev_mutex); > > > } > > > > > > -static int stdp4028_ge_b850v3_fw_probe(struct i2c_client > > > *stdp4028_i2c, > > > - const struct i2c_device_id > > > *id) > > > +static int ge_b850v3_register(void) > > > { > > > + struct i2c_client *stdp4028_i2c = ge_b850v3_lvds_ptr- > > > >stdp4028_i2c; > > > struct device *dev = &stdp4028_i2c->dev; > > > - int ret; > > > - > > > - ret = ge_b850v3_lvds_init(dev); > > > - > > > - if (ret) > > > - return ret; > > > - > > > - ge_b850v3_lvds_ptr->stdp4028_i2c = stdp4028_i2c; > > > - i2c_set_clientdata(stdp4028_i2c, ge_b850v3_lvds_ptr); > > > > > > /* drm bridge initialization */ > > > ge_b850v3_lvds_ptr->bridge.funcs = &ge_b850v3_lvds_funcs; > > > @@ -343,6 +334,27 @@ static int stdp4028_ge_b850v3_fw_probe(struct > > > i2c_client *stdp4028_i2c, > > > "ge-b850v3-lvds-dp", ge_b850v3_lvds_ptr); > > > } > > > > > > +static int stdp4028_ge_b850v3_fw_probe(struct i2c_client > > > *stdp4028_i2c, > > > + const struct i2c_device_id > > > *id) > > > +{ > > > + struct device *dev = &stdp4028_i2c->dev; > > > + int ret; > > > + > > > + ret = ge_b850v3_lvds_init(dev); > > > + > > > + if (ret) > > > + return ret; > > > + > > > + ge_b850v3_lvds_ptr->stdp4028_i2c = stdp4028_i2c; > > > + i2c_set_clientdata(stdp4028_i2c, ge_b850v3_lvds_ptr); > > > + > > > + /* Only register after both bridges are probed */ > > > + if (!(ge_b850v3_lvds_ptr->stdp2690_i2c && ge_b850v3_lvds_ptr- > > > >stdp4028_i2c)) > > > > ge_b850v3_lvds_ptr->stdp4028_i2c was just assigned, is there any > > situation it wouldn't be assigned here? > > > > stdp2690_ge_b850v3_fw_probe() seems to contain an identical snippet, > > so I assume symmetry is why both stdp2690_i2c and stdp4028_i2c are > > checked in both locations. Unless you think otherwise, I would suggest > > removing the stdp4028_i2c check from stdp4028_ge_b850v3_fw_probe() and > > the stdp2690_i2c check from stdp2690_ge_b850v3_fw_probe(). > > > > Yeah - I can drop that as you have said. > > > > + return 0; > > > > My reading of this code is that stdp4028_ge_b850v3_fw_probe() and > > stdp2690_ge_b850v3_fw_probe() are racing, and the 2nd driver to probe > > will go ahead and call ge_b850v3_register(). Is there any reason why > > EPROBE_DEFER isn't used here? > > > > The issue is that the way these are (pre)configured and wired up in the > device, monitor detection is performed by one chip and the other chip > is wired for access to the edid. > > If the probe for the chip handling presence detection (4028) is > registered before the EDID access is properly setup, it tries to > perform an EDID access, resulting in the panic. > > As mentioned in the original commit[1] for this driver, the two bridges > here have custom firmware, as a result neither the STDP4028 > nor the STDP2690 behave as the stock bridges would. The drive isn't > able to control the video processing pipeline as a result, with the > driver mainly needed to perform hot plug detection and read the EDID. > > As the bridges basically function as one custom bridge in this > instance, the approach I've taken is to ensure that both parts are > initialised before registering as this avoided the need to defer. Thanks for explaining this. With the above fix, looks good to me! Reviewed-by: Robert Foss > > Martyn > > > [1] > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c?id=fcfa0ddc18ed2100fbe80d15a543846b629774c0 > > > > + > > > + return ge_b850v3_register(); > > > +} > > > + > > > static int stdp4028_ge_b850v3_fw_remove(struct i2c_client > > > *stdp4028_i2c) > > > { > > > ge_b850v3_lvds_remove(); > > > @@ -386,7 +398,11 @@ static int stdp2690_ge_b850v3_fw_probe(struct > > > i2c_client *stdp2690_i2c, > > > ge_b850v3_lvds_ptr->stdp2690_i2c = stdp2690_i2c; > > > i2c_set_clientdata(stdp2690_i2c, ge_b850v3_lvds_ptr); > > > > > > - return 0; > > > + /* Only register after both bridges are probed */ > > > + if (!(ge_b850v3_lvds_ptr->stdp2690_i2c && ge_b850v3_lvds_ptr- > > > >stdp4028_i2c)) > > > + return 0; > > > + > > > + return ge_b850v3_register(); > > > } > > > > > > static int stdp2690_ge_b850v3_fw_remove(struct i2c_client > > > *stdp2690_i2c) > > > -- > > > 2.33.0 > > > >