From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 8D871221DAD; Tue, 10 Mar 2026 04:58:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773118729; cv=none; b=CrXxGJxHwbeH3FpCwtZUht1JHYQR9D5tz+coZZUoXwEoF94jNlFFY7QaVQNoLaBCGpwPw7eKHXbRMyKrDspuNkcGwCheoxO+IQ180Zb2GyKTkQVw4r6DOD4Aly6WrDasgFtPW6lECplyJaGozPwTTFr8o1uxXc69mTol8nQakNQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773118729; c=relaxed/simple; bh=JuB3BBlaH8QMjjqlhAeA7SEGGjrsDEa4xPg7ybMmmPk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=BQ+A+fz5G1+PmLVlMXA4Tr+ASlTL4z791koKVvwNuq1Q6C/+U3JnrueJiS2NY/GcGUtb6Q4rtKdhfSMAg6gudLTXZiNwIzOOCdx8B2g5IsKFhvRlRIMnvHbuI3cQrWV3U0jTgMi26SrmVYFupZraV/HSccioGrVaCr08Et0LqAw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=sEbP38Kg; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="sEbP38Kg" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9C3D3C19423; Tue, 10 Mar 2026 04:58:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773118728; bh=JuB3BBlaH8QMjjqlhAeA7SEGGjrsDEa4xPg7ybMmmPk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sEbP38KgD0Y/oHZXROIDnP+raCdMDtwsbl+bsBTcVv27xQu+WehgToWFUMAdyS0Io 6BBvySH+5/nOZdUM8TzODpyRvRUckCruTavyE1a/WxHUh9FZgFEkT8+llsHR9zzotP 0xG+ORfxAEQZxgSAw0TAa3L8s0ioPxQENpYCOMMGohyLuwo3QRlFYj3Dzp9WGaM5Yo n1S7+La+3K5TumLjJEb8ZG5HTyDO7TVC2Tk/hqv3buwFt/VgyuJJzq9GpsSedwAoPx 46DUZR5JHqxbKgcUItqID8xgSWamoAnR1H/PVZFaNRQbAmNYv0jMgwpTItA2DNEUHB 8XHyMqkcF5w8g== Date: Tue, 10 Mar 2026 10:28:30 +0530 From: Sumit Garg To: Krzysztof Kozlowski Cc: linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-media@vger.kernel.org, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, ath12k@lists.infradead.org, linux-remoteproc@vger.kernel.org, andersson@kernel.org, konradybcio@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, robin.clark@oss.qualcomm.com, sean@poorly.run, akhilpo@oss.qualcomm.com, lumag@kernel.org, abhinav.kumar@linux.dev, jesszhan0024@gmail.com, marijn.suijten@somainline.org, airlied@gmail.com, simona@ffwll.ch, vikash.garodia@oss.qualcomm.com, dikshita.agarwal@oss.qualcomm.com, bod@kernel.org, mchehab@kernel.org, elder@kernel.org, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, jjohnson@kernel.org, mathieu.poirier@linaro.org, trilokkumar.soni@oss.qualcomm.com, mukesh.ojha@oss.qualcomm.com, pavan.kondeti@oss.qualcomm.com, jorge.ramirez@oss.qualcomm.com, tonyh@qti.qualcomm.com, vignesh.viswanathan@oss.qualcomm.com, srinivas.kandagatla@oss.qualcomm.com, amirreza.zarrabi@oss.qualcomm.com, jens.wiklander@linaro.org, op-tee@lists.trustedfirmware.org, apurupa@qti.qualcomm.com, skare@qti.qualcomm.com, Sumit Garg Subject: Re: [PATCH 02/14] firmware: qcom: Add a generic PAS service Message-ID: References: <20260306105027.290375-1-sumit.garg@kernel.org> <20260306105027.290375-3-sumit.garg@kernel.org> <5dab61a6-d8cc-431d-b59e-744d98195d90@kernel.org> <52cd78c2-95e2-4f56-9adc-242b6cf3baab@kernel.org> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Mar 09, 2026 at 12:46:43PM +0530, Sumit Garg wrote: > On Mon, Mar 09, 2026 at 08:10:02AM +0100, Krzysztof Kozlowski wrote: > > On 09/03/2026 05:55, Sumit Garg wrote: > > > On Fri, Mar 06, 2026 at 12:15:01PM +0100, Krzysztof Kozlowski wrote: > > >> On 06/03/2026 11:50, Sumit Garg wrote: > > >>> From: Sumit Garg > > >>> > > >>> Qcom platforms has the legacy of using non-standard SCM calls > > >>> splintered over the various kernel drivers. These SCM calls aren't > > >>> compliant with the standard SMC calling conventions which is a > > >>> prerequisite to enable migration to the FF-A specifications from > > >>> Arm. > > >>> > > >>> OP-TEE as an alternative trusted OS to QTEE can't support these non- > > >>> standard SCM calls. And even for newer architectures QTEE won't be able > > >>> to support SCM calls either with FF-A requirements coming in. And with > > >>> both OP-TEE and QTEE drivers well integrated in the TEE subsystem, it > > >>> makes further sense to reuse the TEE bus client drivers infrastructure. > > >>> > > >>> The added benefit of TEE bus infrastructure is that there is support > > >>> for discoverable/enumerable services. With that client drivers don't > > >>> have to manually invoke a special SCM call to know the service status. > > >>> > > >>> So enable the generic Peripheral Authentication Service (PAS) provided > > >>> by the firmware. It acts as the common layer with different TZ > > >>> backends plugged in whether it's an SCM implementation or a proper > > >>> TEE bus based PAS service implementation. > > >>> > > >>> Signed-off-by: Sumit Garg > > >>> --- > > >>> drivers/firmware/qcom/Kconfig | 8 + > > >>> drivers/firmware/qcom/Makefile | 1 + > > >>> drivers/firmware/qcom/qcom_pas.c | 295 +++++++++++++++++++++++++ > > >>> drivers/firmware/qcom/qcom_pas.h | 53 +++++ > > >>> include/linux/firmware/qcom/qcom_pas.h | 41 ++++ > > >>> 5 files changed, 398 insertions(+) > > >>> create mode 100644 drivers/firmware/qcom/qcom_pas.c > > >>> create mode 100644 drivers/firmware/qcom/qcom_pas.h > > >>> create mode 100644 include/linux/firmware/qcom/qcom_pas.h > > >>> > > >>> diff --git a/drivers/firmware/qcom/Kconfig b/drivers/firmware/qcom/Kconfig > > >>> index b477d54b495a..8653639d06db 100644 > > >>> --- a/drivers/firmware/qcom/Kconfig > > >>> +++ b/drivers/firmware/qcom/Kconfig > > >>> @@ -6,6 +6,14 @@ > > >>> > > >>> menu "Qualcomm firmware drivers" > > >>> > > >>> +config QCOM_PAS > > >>> + tristate > > >>> + help > > >>> + Enable the generic Peripheral Authentication Service (PAS) provided > > >>> + by the firmware. It acts as the common layer with different TZ > > >>> + backends plugged in whether it's an SCM implementation or a proper > > >>> + TEE bus based PAS service implementation. > > >>> + > > >>> config QCOM_SCM > > >>> select QCOM_TZMEM > > >>> tristate > > >>> diff --git a/drivers/firmware/qcom/Makefile b/drivers/firmware/qcom/Makefile > > >>> index 0be40a1abc13..dc5ab45f906a 100644 > > >>> --- a/drivers/firmware/qcom/Makefile > > >>> +++ b/drivers/firmware/qcom/Makefile > > >>> @@ -8,3 +8,4 @@ qcom-scm-objs += qcom_scm.o qcom_scm-smc.o qcom_scm-legacy.o > > >>> obj-$(CONFIG_QCOM_TZMEM) += qcom_tzmem.o > > >>> obj-$(CONFIG_QCOM_QSEECOM) += qcom_qseecom.o > > >>> obj-$(CONFIG_QCOM_QSEECOM_UEFISECAPP) += qcom_qseecom_uefisecapp.o > > >>> +obj-$(CONFIG_QCOM_PAS) += qcom_pas.o > > >>> diff --git a/drivers/firmware/qcom/qcom_pas.c b/drivers/firmware/qcom/qcom_pas.c > > >>> new file mode 100644 > > >>> index 000000000000..dc04ff1b6be0 > > >>> --- /dev/null > > >>> +++ b/drivers/firmware/qcom/qcom_pas.c > > >>> @@ -0,0 +1,295 @@ > > >>> +// SPDX-License-Identifier: GPL-2.0 > > >>> +/* > > >>> + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries. > > >>> + */ > > >>> + > > >>> +#include > > >>> +#include > > >>> +#include > > >>> +#include > > >>> +#include > > >>> +#include > > >>> +#include > > >>> + > > >>> +#include "qcom_pas.h" > > >>> +#include "qcom_scm.h" > > >>> + > > >>> +static struct qcom_pas_ops *ops_ptr; > > >> > > >> I really dislike this singleton design. And it is not even needed! If > > >> you were storing here some allocated instance of SCM/PAS I could > > >> understand, but singleton for only ops? Just implement one driver (so > > >> SCM + whatever you have here) which will decide which ops to use, > > >> through the probe. Really, this is neither needed nor beneficial. > > > > > > The motivation here is rather quite opposite to the single monolithic > > > SCM driver design. The TZ services like PAS, ICE and so on are going to > > > be implemented as independent discoverable devices on TEE bus which > > > rather needs independent kernel client drivers. > > > > You still have singleton here. So if you think you do opposite to > > singleton, then drop this static. > > Sure. > > > > > > > > > Also, the single driver probe can't work here since the SCM driver is > > > bound to the platform bus whereas the TEE PAS driver is bound to the TEE > > > bus. So there is a reason for the current design. > > > > > >> > > >> It actually leads to more problems with this barrier handling, see > > >> further comments. > > > > > > The barrier handling is something that I carried over from existing > > > implmentation but I can't see a reason why it can't be replaced with a > > > simple mutex. See diff below for mutex. > > > > > >> ... > > >> > > >>> + > > >>> +/** > > >>> + * qcom_pas_shutdown() - Shut down the remote processor > > >>> + * @pas_id: peripheral authentication service id > > >>> + * > > >>> + * Returns 0 on success. > > >>> + */ > > >>> +int qcom_pas_shutdown(u32 pas_id) > > >>> +{ > > >>> + if (ops_ptr) > > >>> + return ops_ptr->shutdown(ops_ptr->dev, pas_id); > > >>> + > > >>> + return -ENODEV; > > >>> +} > > >>> +EXPORT_SYMBOL_GPL(qcom_pas_shutdown); > > >>> + > > >>> +/** > > >>> + * qcom_pas_supported() - Check if the peripheral authentication service is > > >>> + * available for the given peripheral > > >>> + * @pas_id: peripheral authentication service id > > >>> + * > > >>> + * Returns true if PAS is supported for this peripheral, otherwise false. > > >>> + */ > > >>> +bool qcom_pas_supported(u32 pas_id) > > >>> +{ > > >>> + if (ops_ptr) > > >> > > >> Lack of barriers here is not looking right. Existing/old code is not a > > >> good example, I fixed only the obvious issue, but new code should be > > >> correct from the beginning. > > >> > > >> Barriers should normally be always paired, unless you have some clear > > >> path no concurrent execution can happen here, but such explanation is > > >> missing, look: > > > > > > Actually concurrent execution is rather required here since TZ can > > > support parallel bring-up of co-processors. The synchonization is only > > > needed when PAS client drivers are performing a deferred probe waiting > > > for the service to be available. However, you are right explanation is > > > missing here which I will add in the next version. > > > > Hm? Existing comments are completely useless. Your comment said just > > "barrier" basically... That's nothing useful. > > Agree, following is something I plan for v2 (using mutex instead of a > barrier): > > /* > * The ops mutex here is only intended to synchronize when client drivers > * are in parallel checking for PAS service availability. However, once the > * PAS backend becomes available, it is allowed for multiple threads to enter > * TZ for parallel bringup of co-processors during boot. > */ > static DEFINE_MUTEX(ops_mutex); After more testing, it came out that there are corner cases where the registered ops structure writes aren't visible to other cores. So indeed a data barrier is needed instead of mutex. I will add relevant code comments. -Sumit