From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 0C39D2C11D3; Tue, 19 Aug 2025 12:33:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755606804; cv=none; b=XjEzH9pPqRxlZr/HLw3Gfx78mYqMUANkrqH/BEvPbokPwUJ1SPp+xfUpdHQzQRjl0EKLfktefOUksR7nrr4ygqkozYeibNoPi3qxuEwf9TMnsxdpPOL7hGeZIktFXv+waWdxCckaqI9wMY+RMeO4ePA92Qpxs5sbKSOw6WhFNIU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755606804; c=relaxed/simple; bh=BwJdGjVx4p3Eg2GuSRrf3CyAm8Bn8j9VQyyjwV9g7Pw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=bDJVlYDExT3cV+vLcqL4lOp3BJ0GneKqxn9/YE1nn4kRYfx1WPr3jtES/h6S1bQQQVBhuLTucnP8Lnm3QXGP5tRl+9GZKA7AeC2wD3xsgkJ+zutXW45KyYHvxPzOa2kx0Fos32GKi9bYWTagwymORbsbY9BcPs/i5Ph9CBxXjK0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DFC0116A3; Tue, 19 Aug 2025 05:33:12 -0700 (PDT) Received: from pluto (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 15C753F63F; Tue, 19 Aug 2025 05:33:18 -0700 (PDT) Date: Tue, 19 Aug 2025 13:33:10 +0100 From: Cristian Marussi To: Junnan Wu Cc: sudeep.holla@arm.com, cristian.marussi@arm.com, florian.fainelli@broadcom.com, arm-scmi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, lei19.wang@samsung.com, q1.huang@samsung.com Subject: Re: [PATCH] firmware: arm_scmi: Set device ready before register scmi_virtio_driver Message-ID: References: <20250812075343.3201365-1-junnan01.wu@samsung.com> 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=us-ascii Content-Disposition: inline In-Reply-To: <20250812075343.3201365-1-junnan01.wu@samsung.com> On Tue, Aug 12, 2025 at 03:53:43PM +0800, Junnan Wu wrote: > Fix irregularities in scmi driver probe. > Good catch, thanks for this: indeed after the transports have been converted to modules the probe sequence changed a bit and we cannot leverage anymore the virtio_device_ready() called by the core in virtio_dev_probe() since the scmi_vio_probe() does not complete until the core SCMI stack has probed with scmi_probe() which in turn transmits the first BASE protocol exchanges. I did not know about this behaviour of type_1 hyp.. > After 'commit 20bda12a0ea0 ("firmware: arm_scmi: Make VirtIO transport a standalone driver")' > making SCMI VirtIO transport a standalone driver, > `scmi_virtio_probe` will follow `scmi_vio_probe`, > and during `scmi_virtio_probe`, it will do `scmi_probe` which will invoke > function `scmi_protocol_acquire(handle, SCMI_PROTOCOL_BASE)`, > and this function will send message via virtqueue and wait device's reply > > Before this patch, only after `scmi_vio_probe`, > frontend will mark device DRIVER_OK by function `virtio_dev_probe` > in 'drivers/virtio/virtio.c' itself. > > Accroding to chapter '3.1 Device Initialization' in virtio-spec, > ``` > The driver MUST NOT send any buffer available notifications > to the device before setting DRIVER_OK. > ``` > > In some type1-hypervisor, available buffer notifications > will be intercepted until virtio driver is okay. In this case, > `scmi_vio_probe` will be blocked at `scmi_wait_for_reply` > and probe can never complete. > > Therefore, the operation to set DRIVER_OK must follow > perform device-specific setup immediately, > then available buffer notifications can be sent in function `scmi_probe`. > > Fixes: 20bda12a0ea0 ("firmware: arm_scmi: Make VirtIO transport a standalone driver") > Signed-off-by: Junnan Wu > --- > drivers/firmware/arm_scmi/transports/virtio.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/firmware/arm_scmi/transports/virtio.c b/drivers/firmware/arm_scmi/transports/virtio.c > index cb934db9b2b4..326c4a93e44b 100644 > --- a/drivers/firmware/arm_scmi/transports/virtio.c > +++ b/drivers/firmware/arm_scmi/transports/virtio.c > @@ -871,6 +871,9 @@ static int scmi_vio_probe(struct virtio_device *vdev) > /* Ensure initialized scmi_vdev is visible */ > smp_store_mb(scmi_vdev, vdev); > > + /* Set device ready */ > + virtio_device_ready(vdev); > + > ret = platform_driver_register(&scmi_virtio_driver); > if (ret) { > vdev->priv = NULL; ...also, I suppose, that here nothing is to be done on the error path regarding the vdedv status, becasue is already taken care in the error path of virtio_dev_probe()...am I right ? (just confirming..) Maybe you could simplify a bit the commit message but other than this LGTM. Reviewed-by: Cristian Marussi Tested-by: Cristian Marussi Thanks, Cristian