From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 509DE40758C for ; Wed, 8 Jul 2026 09:00:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783501238; cv=none; b=m23tZvxN6YouuBCVBLYNrOT24L4M8J+ymGwM+1fT8QVaIXY3XDdDVq9RKXORQebLs+f4TsfFLP9v6p8up9hMmg7HJdTOQ6knK4q9VKP8KgJgj3XloI9kCZ5KOIOhlAA3X5mVkR5EGBdQ4Mp5tjqt6siHjtNTnKeMoZIqctSqVhM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783501238; c=relaxed/simple; bh=QU7FMbRqZmRrbMTi5MXALu8nDRd3ZSFtbiBzRhVrEVE=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=a8lVGAdG191VNjXTzz+eAaYQkq5Fv2psOBY+17WeOh6d7xy2nxW7/8X2oUSSe0Jb+nkTKJDjVuytCYOJudSFgfLS1Zjw3m5bLoQJCZq7hcdegvIcnuZPIoSpghEkGz2Y8OH4vkuskBa0qRjsy5wSf8u20gWfXnrzR8kQAmPt8xE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HJEiVZsP; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HJEiVZsP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E438C1F000E9; Wed, 8 Jul 2026 09:00:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783501235; bh=1/1+F1RFMl2GV9XWTGIsSj/agttsISF6u+8SbWZvUWE=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=HJEiVZsPywwMg6M5aHHmJM3FibXT6peOFS+hroRKr5p41D/reu45046H83c/F5nIl 15nhGsyGBFoqkibdcAyq9hdWbH32iknd4RAP80iPNYI8etPiSslov3CWGOyVrNZ0cW 2kiUkbqhrQ1pNC2FDV3d/s0pN66eqaIFu2O9aCoj4QQbDQ9O5WhbpA5K82AmxN2Yju fhGlZzq6kqe3KghAofTydnPLW0Z1W1eYhpogO8zbJNPYfgJtHX/m/zAHjs6KV6ipAY 3YntcNZVrYMNDIUGw9O++miscbE7NzDBipJoUIk/C+t3LLonrJuG86f4y1v1nKu0g+ s5KUFBqbtoGww== From: Sudeep Holla Date: Wed, 08 Jul 2026 10:00:07 +0100 Subject: [PATCH v4 11/16] firmware: arm_scmi: Clear SystemPower flag on create failure Precedence: bulk X-Mailing-List: arm-scmi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260708-scmi_core_fixes-v4-11-53142cd60b63@kernel.org> References: <20260708-scmi_core_fixes-v4-0-53142cd60b63@kernel.org> In-Reply-To: <20260708-scmi_core_fixes-v4-0-53142cd60b63@kernel.org> To: arm-scmi@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Cristian Marussi X-Mailer: b4 0.15.2 __scmi_device_create() reserves the singleton SystemPower protocol device before registering the SCMI device. If any later step fails, a stale reservation can make a later retry reject SystemPower device creation permanently, for example after probe deferral. A plain global boolean is not enough to track the reservation. A delayed final release of an older SystemPower device could clear the boolean after a newer device has already claimed it, breaking the singleton guarantee for the active device. Track the reservation with the scmi_device pointer itself. Claim it with cmpxchg(NULL, scmi_dev) after allocating the device object, and release it with cmpxchg(scmi_dev, NULL) from the common cleanup helper. This lets the create-failure, explicit destroy and final release paths clear only the reservation owned by the device being cleaned up. Fixes: 2c3e674465e7 ("firmware: arm_scmi: Refactor device create/destroy helpers") Reported-by: Sashiko Signed-off-by: Sudeep Holla --- drivers/firmware/arm_scmi/bus.c | 59 ++++++++++++++++++++++------------------- 1 file changed, 32 insertions(+), 27 deletions(-) diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c index 793be9eabaed..dcaefc1aa892 100644 --- a/drivers/firmware/arm_scmi/bus.c +++ b/drivers/firmware/arm_scmi/bus.c @@ -7,7 +7,6 @@ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt -#include #include #include #include @@ -33,8 +32,8 @@ struct scmi_requested_dev { struct list_head node; }; -/* Track globally the creation of SCMI SystemPower related devices */ -static atomic_t scmi_syspower_registered = ATOMIC_INIT(0); +/* Track globally the SCMI SystemPower protocol device. */ +static struct scmi_device *scmi_syspower_registered; /** * scmi_protocol_device_request - Helper to request a device @@ -391,10 +390,17 @@ void scmi_driver_unregister(struct scmi_driver *driver) } EXPORT_SYMBOL_GPL(scmi_driver_unregister); +static void scmi_device_release_syspower(struct scmi_device *scmi_dev) +{ + if (scmi_dev->protocol_id == SCMI_PROTOCOL_SYSTEM) + cmpxchg(&scmi_syspower_registered, scmi_dev, NULL); +} + static void scmi_device_release(struct device *dev) { struct scmi_device *scmi_dev = to_scmi_dev(dev); + scmi_device_release_syspower(scmi_dev); kfree_const(scmi_dev->name); kfree(scmi_dev); } @@ -406,9 +412,7 @@ static void __scmi_device_destroy(struct scmi_device *scmi_dev) dev_name(&scmi_dev->dev), scmi_dev->protocol_id, scmi_dev->name); - if (scmi_dev->protocol_id == SCMI_PROTOCOL_SYSTEM) - atomic_set(&scmi_syspower_registered, 0); - + scmi_device_release_syspower(scmi_dev); ida_free(&scmi_bus_id, scmi_dev->id); device_unregister(&scmi_dev->dev); } @@ -419,6 +423,7 @@ __scmi_device_create(struct device_node *np, struct device *parent, { int id, retval; struct scmi_device *scmi_dev; + bool syspower = (protocol == SCMI_PROTOCOL_SYSTEM); /* * If the same protocol/name device already exist under the same parent @@ -431,39 +436,33 @@ __scmi_device_create(struct device_node *np, struct device *parent, if (scmi_dev) return scmi_dev; + scmi_dev = kzalloc_obj(*scmi_dev); + if (!scmi_dev) + return NULL; + + scmi_dev->protocol_id = protocol; + /* - * Ignore any possible subsequent failures while creating the device - * since we are doomed anyway at that point; not using a mutex which - * spans across this whole function to keep things simple and to avoid - * to serialize all the __scmi_device_create calls across possibly - * different SCMI server instances (parent) + * Reserve the singleton SystemPower protocol device using the device + * pointer itself, so delayed release of an older device cannot clear + * a reservation owned by a newer device. */ - if (protocol == SCMI_PROTOCOL_SYSTEM && - atomic_cmpxchg(&scmi_syspower_registered, 0, 1)) { + if (syspower && cmpxchg(&scmi_syspower_registered, NULL, scmi_dev)) { dev_warn(parent, "SCMI SystemPower protocol device must be unique !\n"); + kfree(scmi_dev); return NULL; } - scmi_dev = kzalloc_obj(*scmi_dev); - if (!scmi_dev) - return NULL; - scmi_dev->name = kstrdup_const(name ?: "unknown", GFP_KERNEL); - if (!scmi_dev->name) { - kfree(scmi_dev); - return NULL; - } + if (!scmi_dev->name) + goto free_dev; id = ida_alloc_min(&scmi_bus_id, 1, GFP_KERNEL); - if (id < 0) { - kfree_const(scmi_dev->name); - kfree(scmi_dev); - return NULL; - } + if (id < 0) + goto free_name; scmi_dev->id = id; - scmi_dev->protocol_id = protocol; scmi_dev->dev.parent = parent; device_set_node(&scmi_dev->dev, of_fwnode_handle(np)); scmi_dev->dev.bus = &scmi_bus_type; @@ -482,6 +481,12 @@ __scmi_device_create(struct device_node *np, struct device *parent, put_device(&scmi_dev->dev); ida_free(&scmi_bus_id, id); return NULL; +free_name: + kfree_const(scmi_dev->name); +free_dev: + scmi_device_release_syspower(scmi_dev); + kfree(scmi_dev); + return NULL; } static struct scmi_device * -- 2.43.0