From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailout1.w1.samsung.com (mailout1.w1.samsung.com [210.118.77.11]) (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 E1CED32548C for ; Mon, 5 Jan 2026 18:16:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=210.118.77.11 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767636971; cv=none; b=APR2qAbp/lK2ajk8xNhIGKpM0LcCikWQmQaNGOHiVu5zS1ZySeOWXEHGd0LhHLZX471GDhaFZn+Ika1/8O+Su+IlSyatanK+Ajpkt21WBFj5QtDjgh45aJGPLtJ2lhOP+opZk4jxGbGSRoTjfFEt9KufyffbUF7TkwAjats0AiM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767636971; c=relaxed/simple; bh=A7gNXNFB8xRtDfZr1V3EN/I8adhlhmCKGYrl7EFiLoI=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:In-Reply-To: Content-Type:References; b=P0uJmBVuase6iEJVX6NI42WJu5w75qplOp15xOss3G0s+znZhMIEr2V86Oh1uLu4qCe/SFJgvjpbQwUETanaEfbjm4VrZ/EBhMvkYXGcOc9xMHq+lw289z8jWkuek9tIl5QviU+JOZpD0U4PE3ehBoPeX+wLA5S2G/L7DTYwPG8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=samsung.com; spf=pass smtp.mailfrom=samsung.com; dkim=pass (1024-bit key) header.d=samsung.com header.i=@samsung.com header.b=gfCIieX/; arc=none smtp.client-ip=210.118.77.11 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=samsung.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=samsung.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=samsung.com header.i=@samsung.com header.b="gfCIieX/" Received: from eucas1p2.samsung.com (unknown [182.198.249.207]) by mailout1.w1.samsung.com (KnoxPortal) with ESMTP id 20260105181604euoutp01dd476878a112796e29a1133a852167dc~H6HRH5TbE1400614006euoutp01e for ; Mon, 5 Jan 2026 18:16:04 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 mailout1.w1.samsung.com 20260105181604euoutp01dd476878a112796e29a1133a852167dc~H6HRH5TbE1400614006euoutp01e DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=samsung.com; s=mail20170921; t=1767636964; bh=CZpNhKgKBUJeeJlb2Oj06Qm6plDvlhoN1tV/Sntfu10=; h=Date:Subject:From:To:Cc:In-Reply-To:References:From; b=gfCIieX/XAsyYCo75g4mZmzjGDpxvJBlfMKZx8sp1OERx3qDFULmGlANtdm4Jmlki 82NHg+pIzyibAf+uJcHKy/ybh+0ph4T+tFzLgG12hKwjdk57rA9hxX2ZFLKGs8F9sy TuDpbwBP9lfhc+d7KDRvc2ozr0oFILwk7jme4SKw= Received: from eusmtip1.samsung.com (unknown [203.254.199.221]) by eucas1p2.samsung.com (KnoxPortal) with ESMTPA id 20260105181604eucas1p2c0c3f917560e8deda5dfa5b7cd09ac89~H6HQ8FGc61567315673eucas1p2U; Mon, 5 Jan 2026 18:16:04 +0000 (GMT) Received: from [106.210.134.192] (unknown [106.210.134.192]) by eusmtip1.samsung.com (KnoxPortal) with ESMTPA id 20260105181603eusmtip1c8f3f9a01d1f78ce46a688dc2d0392da~H6HPvItmA0426604266eusmtip1f; Mon, 5 Jan 2026 18:16:02 +0000 (GMT) Message-ID: Date: Mon, 5 Jan 2026 19:16:00 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Betterbird (Windows) Subject: Re: [PATCH 3/3] gpio: shared: allow sharing a reset-gpios pin between reset-gpio and gpiolib From: Marek Szyprowski To: Bartosz Golaszewski Cc: Bartosz Golaszewski , Linus Walleij , linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org Content-Language: en-US In-Reply-To: <3cb799ed-6760-481b-991d-5d90a23b9128@samsung.com> Content-Transfer-Encoding: 8bit X-CMS-MailID: 20260105181604eucas1p2c0c3f917560e8deda5dfa5b7cd09ac89 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20260105115023eucas1p1af1f8e80041f94843beb664966894fb9 X-EPHeader: CA X-CMS-RootMailID: 20260105115023eucas1p1af1f8e80041f94843beb664966894fb9 References: <20251222-gpio-shared-reset-gpio-proxy-v1-0-8d4bba7d8c14@oss.qualcomm.com> <20251222-gpio-shared-reset-gpio-proxy-v1-3-8d4bba7d8c14@oss.qualcomm.com> <00107523-7737-4b92-a785-14ce4e93b8cb@samsung.com> <3cb799ed-6760-481b-991d-5d90a23b9128@samsung.com> On 05.01.2026 18:26, Marek Szyprowski wrote: > On 05.01.2026 13:28, Bartosz Golaszewski wrote: >> On Mon, Jan 5, 2026 at 12:50 PM Marek Szyprowski >> wrote: >>> On 22.12.2025 11:01, Bartosz Golaszewski wrote: >>>> We currently support sharing GPIOs between multiple devices whose >>>> drivers >>>> use either the GPIOLIB API *OR* the reset control API but not both at >>>> the same time. >>>> >>>> There's an unlikely corner-case where a reset-gpios pin can be >>>> shared by >>>> one driver using the GPIOLIB API and a second using the reset API. >>>> This >>>> will currently not work as the reset-gpio consumers are not >>>> described in >>>> firmware at the time of scanning so the shared GPIO just chooses >>>> one of >>>> the proxies created for the consumers when the reset-gpio driver >>>> performs >>>> the lookup. This can of course conflict in the case described above. >>>> >>>> In order to fix it: if we deal with the "reset-gpios" pin that's >>>> shared >>>> acconding to the firmware node setup, create a proxy for each >>>> described >>>> consumer as well as another one for the potential reset-gpio >>>> device. To >>>> that end: rework the matching to take this into account. >>>> >>>> Fixes: 7b78b26757e0 ("gpio: shared: handle the reset-gpios corner >>>> case") >>>> Signed-off-by: Bartosz Golaszewski >>>> >>> This patch landed in linux-next as commit 49416483a953 ("gpio: shared: >>> allow sharing a reset-gpios pin between reset-gpio and gpiolib"). In my >>> tests I found that it breaks booting and triggers warnings on some >>> of my >>> test boards. Reverting it on top of next-20260105 fixes those issues. >>> Let me know if I can help debugging this issue. >>> >>> >>> Here are relevant logs from my 3 test systems: >>> >> Thanks for the report. >> >> Nice combo, it looks like these are three separate bugs... >> >>> 1. Samsung TM2e - arch/arm64/boot/dts/exynos/exynos5433-tm2e.dts >>> >>> exynos-dsi 13900000.dsi: [drm:samsung_dsim_host_attach] Attached >>> s6e3hf2 >>> device (lanes:4 bpp:24 mode-flags:0x6e0) >>> Unable to handle kernel NULL pointer dereference at virtual address >> Could you use faddr2line to point me to the exact offending line? This >> would speed up the debugging. > > I need some time to get that output, but this issue is caused by a > devm_gpiod_get_optional() call for a gpio that is not defined for that > board. > I think that everything is in the call stack: Call trace:  gpiod_direction_input_nonotify+0x20/0x39c (P)  gpiod_configure_flags+0x23c/0x480  gpiod_find_and_request+0x1a0/0x574  gpiod_get_index+0x58/0x84  devm_gpiod_get_index+0x20/0xb4  devm_gpiod_get_optional+0x18/0x30  samsung_dsim_host_attach+0x1c8/0x284  mipi_dsi_attach+0x30/0x54  s6e3ha2_probe+0x148/0x200 [panel_samsung_s6e3ha2] ... The issue is in gpiod_direction_input_nonotify+0x20/0x39c: $ grep gpiod_direction_input_nonotify System.map ffff800080810360 T gpiod_direction_input_nonotify $ aarch64-linux-gnu-addr2line -f -e vmlinux ffff800080810380 class_gpio_chip_guard_constructor /home/m.szyprowski/dev/kernel/linux-next/drivers/gpio/gpiolib.h:231 IMHO it looks that gpiod_configure_flags() is called for NULL gpio_chip. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland