Subject: [RFC 3/3] VFIO: platform: add vfio-platform-calxedaxgmac driver

From: [email-masked] (Eric Auger)
Date: Fri, 17 Apr 2015 17:01:11 +0200

Hi Alex,
On 04/17/2015 04:29 PM, Alex Williamson wrote:
> On Fri, 2015-04-17 at 15:37 +0200, Eric Auger wrote:
>> This patch introduces a specialized vfio platform driver for the
>> calxeda xgmac. On top of the generic vfio platform driver functionalities,
>> it implements the reset modality.  This latter basically disables interrupts
>> and stops DMA transfers.
>>
>> Code is inherited from calxeda xgmac native driver
>>
>> Signed-off-by: Eric Auger <[email-masked]>
>> ---
>>  drivers/vfio/platform/Kconfig                      |   2 +
>>  drivers/vfio/platform/Makefile                     |   2 +
>>  drivers/vfio/platform/reset/Kconfig                |   7 ++
>>  drivers/vfio/platform/reset/Makefile               |   5 +
>>  .../platform/reset/vfio_platform_calxedaxgmac.c    | 109 +++++++++++++++++++++
>>  5 files changed, 125 insertions(+)
>>  create mode 100644 drivers/vfio/platform/reset/Kconfig
>>  create mode 100644 drivers/vfio/platform/reset/Makefile
>>  create mode 100644 drivers/vfio/platform/reset/vfio_platform_calxedaxgmac.c
>>
>> diff --git a/drivers/vfio/platform/Kconfig b/drivers/vfio/platform/Kconfig
>> index 9a4403e..1df7477 100644
>> --- a/drivers/vfio/platform/Kconfig
>> +++ b/drivers/vfio/platform/Kconfig
>> @@ -18,3 +18,5 @@ config VFIO_AMBA
>>  	  framework.
>>  
>>  	  If you don't know what to do here, say N.
>> +
>> +source "drivers/vfio/platform/reset/Kconfig"
>> diff --git a/drivers/vfio/platform/Makefile b/drivers/vfio/platform/Makefile
>> index 81de144..9ce8afe 100644
>> --- a/drivers/vfio/platform/Makefile
>> +++ b/drivers/vfio/platform/Makefile
>> @@ -2,7 +2,9 @@
>>  vfio-platform-y := vfio_platform.o vfio_platform_common.o vfio_platform_irq.o
>>  
>>  obj-$(CONFIG_VFIO_PLATFORM) += vfio-platform.o
>> +obj-$(CONFIG_VFIO_PLATFORM) += reset/
>>  
>>  vfio-amba-y := vfio_amba.o
>>  
>>  obj-$(CONFIG_VFIO_AMBA) += vfio-amba.o
>> +obj-$(CONFIG_VFIO_AMBA) += reset/
>> diff --git a/drivers/vfio/platform/reset/Kconfig b/drivers/vfio/platform/reset/Kconfig
>> new file mode 100644
>> index 0000000..2c09cea
>> --- /dev/null
>> +++ b/drivers/vfio/platform/reset/Kconfig
>> @@ -0,0 +1,7 @@
>> +config VFIO_PLATFORM_CALXEDAXGMAC
>> +	tristate "VFIO support for calxeda xgmac"
>> +	depends on VFIO_PLATFORM
>> +	help
>> +	  Support for VFIO platform driver specialized for Calxeda xgmac reset.
>> +
>> +	  If you don't know what to do here, say N.
>> diff --git a/drivers/vfio/platform/reset/Makefile b/drivers/vfio/platform/reset/Makefile
>> new file mode 100644
>> index 0000000..8977721
>> --- /dev/null
>> +++ b/drivers/vfio/platform/reset/Makefile
>> @@ -0,0 +1,5 @@
>> +vfio-platform-calxedaxgmac-y := vfio_platform_calxedaxgmac.o
>> +
>> +ccflags-y += -Idrivers/vfio/platform
>> +
>> +obj-$(CONFIG_VFIO_PLATFORM_CALXEDAXGMAC) += vfio-platform-calxedaxgmac.o
>> diff --git a/drivers/vfio/platform/reset/vfio_platform_calxedaxgmac.c b/drivers/vfio/platform/reset/vfio_platform_calxedaxgmac.c
>> new file mode 100644
>> index 0000000..729d0cd
>> --- /dev/null
>> +++ b/drivers/vfio/platform/reset/vfio_platform_calxedaxgmac.c
>> @@ -0,0 +1,109 @@
>> +/*
>> + * VFIO platform driver specialized for Calxeda xgmac reset
>> + * reset code is inherited from calxeda xgmac native driver
>> + *
>> + * Copyright 2010-2011 Calxeda, Inc.
>> + * Copyright (c) 2015 Linaro Ltd.
>> + *              www.linaro.org
>> + *
>> + * This program is free software; you can redistribute it and/or modify it
>> + * under the terms and conditions of the GNU General Public License,
>> + * version 2, as published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope it will be useful, but WITHOUT
>> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
>> + * more details.
>> + *
>> + * You should have received a copy of the GNU General Public License along with
>> + * this program.  If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/kernel.h>
>> +#include <linux/init.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/slab.h>
>> +#include <linux/vfio.h>
>> +#include "vfio_platform_private.h"
>> +#include <linux/io.h>
>> +
>> +#define DRIVER_VERSION  "0.1"
>> +#define DRIVER_AUTHOR   "Eric Auger <[email-masked]>"
>> +#define DRIVER_DESC     "VFIO - Calxeda xgmac vfio platform driver"
>> +
>> +/* XGMAC Register definitions */
>> +#define XGMAC_CONTROL           0x00000000      /* MAC Configuration */
>> +
>> +/* DMA Control and Status Registers */
>> +#define XGMAC_DMA_CONTROL       0x00000f18      /* Ctrl (Operational Mode) */
>> +#define XGMAC_DMA_INTR_ENA      0x00000f1c      /* Interrupt Enable */
>> +
>> +/* DMA Control registe defines */
>> +#define DMA_CONTROL_ST          0x00002000      /* Start/Stop Transmission */
>> +#define DMA_CONTROL_SR          0x00000002      /* Start/Stop Receive */
>> +
>> +/* Common MAC defines */
>> +#define MAC_ENABLE_TX           0x00000008      /* Transmitter Enable */
>> +#define MAC_ENABLE_RX           0x00000004      /* Receiver Enable */
>> +
>> +static inline void xgmac_mac_disable(void __iomem *ioaddr)
>> +{
>> +	u32 value = readl(ioaddr + XGMAC_DMA_CONTROL);
>> +
>> +	value &= ~(DMA_CONTROL_ST | DMA_CONTROL_SR);
>> +	writel(value, ioaddr + XGMAC_DMA_CONTROL);
>> +
>> +	value = readl(ioaddr + XGMAC_CONTROL);
>> +	value &= ~(MAC_ENABLE_TX | MAC_ENABLE_RX);
>> +	writel(value, ioaddr + XGMAC_CONTROL);
>> +}
>> +
>> +static int vfio_platform_calxedaxgmac_reset(struct vfio_platform_device *vdev)
>> +{
>> +	struct resource *res = get_platform_resource(vdev, 0);
>> +	void __iomem *base = phys_to_virt(res->start);
>> +
>> +	if (!base)
>> +		return -ENOMEM;
>> +
>> +	/* disable IRQ */
>> +	writel(0, base + XGMAC_DMA_INTR_ENA);
>> +
>> +	/* Disable the MAC core */
>> +	xgmac_mac_disable(base);
>> +
>> +	return 0;
>> +}
>> +
>> +static int vfio_platform_calxedaxgmac_probe(struct platform_device *pdev)
>> +{
>> +	int ret;
>> +	struct vfio_device *vfio_dev;
>> +	struct vfio_platform_device *vpdev;
>> +
>> +	ret = vfio_platform_probe(pdev);
>> +	if (ret)
>> +		return ret;
>> +
>> +	vfio_dev = vfio_device_get_from_dev(&pdev->dev),
>> +	vpdev = (struct vfio_platform_device *) vfio_device_data(vfio_dev);
>> +	vpdev->reset = vfio_platform_calxedaxgmac_reset;
>> +
>> +	return ret;
>> +}
>> +
>> +static struct platform_driver vfio_platform_calxedaxgmac_driver = {
>> +	.driver = {
>> +		.name = "vfio-platform-calxedaxgmac",
>> +	},
>> +	.probe = vfio_platform_calxedaxgmac_probe,
>> +	.remove = vfio_platform_remove,
>> +};
>> +
>> +module_platform_driver(vfio_platform_calxedaxgmac_driver);
>> +
>> +MODULE_VERSION(DRIVER_VERSION);
>> +MODULE_LICENSE("GPL v2");
>> +MODULE_AUTHOR(DRIVER_AUTHOR);
>> +MODULE_DESCRIPTION(DRIVER_DESC);
> 
> I don't really understand why this needs to be a new driver that wraps
> around the vfio platform driver rather than just an entry in a table of
> available device specific reset functions, setup through the normal
> probe path.  Do we really have no clue what the device is to be able to
> attach a reset function to it from the base vfio platform code?  This
> also seems like a pain for users, who now need to figure out which
> vfio_platform driver to bind to a given device.  If the user can figure
> that out, why can't the kernel just pick the right reset callback for
> them?  Thanks,

Yes I can do the proposed way. I can get access to the compat string of
the device and according to that info I will choose some proper reset
function. I will respin shortly taking into account the other comments.

Thanks!

Eric
> Alex