linux-kernel - Re: [RFC v3 2/2] vfio/platform: msi: add Broadcom platform devices

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Date:   Tue, 12 Jan 2021 10:22:20 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     Vikas Gupta <vikas.gupta@...adcom.com>, alex.williamson@...hat.com,
        cohuck@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     vikram.prakash@...adcom.com, srinath.mannam@...adcom.com,
        ashwin.kamath@...adcom.com, zachary.schroff@...adcom.com,
        manish.kurup@...adcom.com
Subject: Re: [RFC v3 2/2] vfio/platform: msi: add Broadcom platform devices

Hi Vikas,

On 12/14/20 6:45 PM, Vikas Gupta wrote:
> Add msi support for Broadcom platform devices
> 
> Signed-off-by: Vikas Gupta <vikas.gupta@...adcom.com>
> ---
>  drivers/vfio/platform/Kconfig                 |  1 +
>  drivers/vfio/platform/Makefile                |  1 +
>  drivers/vfio/platform/msi/Kconfig             |  9 ++++
>  drivers/vfio/platform/msi/Makefile            |  2 +
>  .../vfio/platform/msi/vfio_platform_bcmplt.c  | 49 +++++++++++++++++++
>  5 files changed, 62 insertions(+)
>  create mode 100644 drivers/vfio/platform/msi/Kconfig
>  create mode 100644 drivers/vfio/platform/msi/Makefile
>  create mode 100644 drivers/vfio/platform/msi/vfio_platform_bcmplt.c
what does plt mean?
> 
> diff --git a/drivers/vfio/platform/Kconfig b/drivers/vfio/platform/Kconfig
> index dc1a3c44f2c6..7b8696febe61 100644
> --- a/drivers/vfio/platform/Kconfig
> +++ b/drivers/vfio/platform/Kconfig
> @@ -21,3 +21,4 @@ config VFIO_AMBA
>  	  If you don't know what to do here, say N.
>  
>  source "drivers/vfio/platform/reset/Kconfig"
> +source "drivers/vfio/platform/msi/Kconfig"
> diff --git a/drivers/vfio/platform/Makefile b/drivers/vfio/platform/Makefile
> index 3f3a24e7c4ef..9ccdcdbf0e7e 100644
> --- a/drivers/vfio/platform/Makefile
> +++ b/drivers/vfio/platform/Makefile
> @@ -5,6 +5,7 @@ vfio-platform-y := vfio_platform.o
>  obj-$(CONFIG_VFIO_PLATFORM) += vfio-platform.o
>  obj-$(CONFIG_VFIO_PLATFORM) += vfio-platform-base.o
>  obj-$(CONFIG_VFIO_PLATFORM) += reset/
> +obj-$(CONFIG_VFIO_PLATFORM) += msi/
>  
>  vfio-amba-y := vfio_amba.o
>  
> diff --git a/drivers/vfio/platform/msi/Kconfig b/drivers/vfio/platform/msi/Kconfig
> new file mode 100644
> index 000000000000..54d6b70e1e32
> --- /dev/null
> +++ b/drivers/vfio/platform/msi/Kconfig
> @@ -0,0 +1,9 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +config VFIO_PLATFORM_BCMPLT_MSI
> +	tristate "MSI support for Broadcom platform devices"
> +	depends on VFIO_PLATFORM && (ARCH_BCM_IPROC || COMPILE_TEST)
> +	default ARCH_BCM_IPROC
> +	help
> +	  Enables the VFIO platform driver to handle msi for Broadcom devices
> +
> +	  If you don't know what to do here, say N.
> diff --git a/drivers/vfio/platform/msi/Makefile b/drivers/vfio/platform/msi/Makefile
> new file mode 100644
> index 000000000000..27422d45cecb
> --- /dev/null
> +++ b/drivers/vfio/platform/msi/Makefile
> @@ -0,0 +1,2 @@
> +# SPDX-License-Identifier: GPL-2.0
> +obj-$(CONFIG_VFIO_PLATFORM_BCMPLT_MSI) += vfio_platform_bcmplt.o
> diff --git a/drivers/vfio/platform/msi/vfio_platform_bcmplt.c b/drivers/vfio/platform/msi/vfio_platform_bcmplt.c
> new file mode 100644
> index 000000000000..a074b5e92d77
> --- /dev/null
> +++ b/drivers/vfio/platform/msi/vfio_platform_bcmplt.c
> @@ -0,0 +1,49 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2020 Broadcom.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/interrupt.h>
> +#include <linux/msi.h>
> +#include <linux/vfio.h>
> +
> +#include "../vfio_platform_private.h"
> +
> +#define RING_SIZE		(64 << 10)
> +
> +#define RING_MSI_ADDR_LS	0x03c
> +#define RING_MSI_ADDR_MS	0x040
> +#define RING_MSI_DATA_VALUE	0x064
Those 3 defines would not be needed anymore with that implementation option.
> +
> +static u32 bcm_num_msi(struct vfio_platform_device *vdev)
> +{
> +	struct vfio_platform_region *reg = &vdev->regions[0];
> +
> +	return (reg->size / RING_SIZE);
> +}
> +
> +static struct vfio_platform_msi_node vfio_platform_bcmflexrm_msi_node = {
> +	.owner = THIS_MODULE,
> +	.compat = "brcm,iproc-flexrm-mbox",
> +	.of_get_msi = bcm_num_msi,
> +};
> +
> +static int __init vfio_platform_bcmflexrm_msi_module_init(void)
> +{
> +	__vfio_platform_register_msi(&vfio_platform_bcmflexrm_msi_node);
> +
> +	return 0;
> +}
> +
> +static void __exit vfio_platform_bcmflexrm_msi_module_exit(void)
> +{
> +	vfio_platform_unregister_msi("brcm,iproc-flexrm-mbox");
> +}
> +
> +module_init(vfio_platform_bcmflexrm_msi_module_init);
> +module_exit(vfio_platform_bcmflexrm_msi_module_exit);
One thing I would like to discuss with Alex.

As the reset module is mandated (except if reset_required is forced to
0), I am wondering if we shouldn't try to turn the reset module into a
"specialization" module and put the msi hooks there. I am afraid we may
end up having modules for each and every vfio platform feature
specialization. At the moment that's fully bearable but I can't predict
what's next.

As the mandated feature is the reset capability maybe we could just keep
the config/module name terminology, tune the kconfig help message to
mention the msi support in case of flex-rm?

What do you think?

Thanks

Eric




> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Broadcom");
>