Re: [PATCH v3] vfio: platform: reset: Add Broadcom FlexRM reset module

[Anup Patel]

Hi Eric,

Thanks for the review comments...

On Sat, Jul 29, 2017 at 6:31 PM, Auger Eric <eric.auger@xxxxxxxxxx> wrote:
> Hi Anup,
> On 20/07/2017 13:17, Anup Patel wrote:
>> This patch adds Broadcom FlexRM low-level reset for
>> VFIO platform.
>>
>> It will do the following:
>> 1. Disable/Deactivate each FlexRM ring
>> 2. Flush each FlexRM ring
>>
>> The cleanup sequence for FlexRM rings is adapted from
>> Broadcom FlexRM mailbox driver.
>>
>> Signed-off-by: Anup Patel <anup.patel@xxxxxxxxxxxx>
>> Reviewed-by: Oza Oza <oza.oza@xxxxxxxxxxxx>
>> Reviewed-by: Scott Branden <scott.branden@xxxxxxxxxxxx>
>> ---
>>  drivers/vfio/platform/reset/Kconfig                |  9 +++
>>  drivers/vfio/platform/reset/Makefile               |  1 +
>>  .../vfio/platform/reset/vfio_platform_bcmflexrm.c  | 93 ++++++++++++++++++++++
>>  3 files changed, 103 insertions(+)
>>  create mode 100644 drivers/vfio/platform/reset/vfio_platform_bcmflexrm.c
>>
>> diff --git a/drivers/vfio/platform/reset/Kconfig b/drivers/vfio/platform/reset/Kconfig
>> index 70cccc5..8d8d226 100644
>> --- a/drivers/vfio/platform/reset/Kconfig
>> +++ b/drivers/vfio/platform/reset/Kconfig
>> @@ -13,3 +13,12 @@ config VFIO_PLATFORM_AMDXGBE_RESET
>>         Enables the VFIO platform driver to handle reset for AMD XGBE
>>
>>         If you don't know what to do here, say N.
>> +
>> +config VFIO_PLATFORM_BCMFLEXRM_RESET
>> +     tristate "VFIO support for Broadcom FlexRM reset"
>> +     depends on VFIO_PLATFORM
>> +     depends on ARCH_BCM_IPROC || COMPILE_TEST
> depends on VFIO_PLATFORM && (ARCH_BCM_IPROC || COMPILE_TEST)?

OK, I will update this.

>> +     help
>> +       Enables the VFIO platform driver to handle reset for Broadcom FlexRM
>> +
>> +       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
>> index 93f4e23..8d9874b 100644
>> --- a/drivers/vfio/platform/reset/Makefile
>> +++ b/drivers/vfio/platform/reset/Makefile
>> @@ -5,3 +5,4 @@ ccflags-y += -Idrivers/vfio/platform
>>
>>  obj-$(CONFIG_VFIO_PLATFORM_CALXEDAXGMAC_RESET) += vfio-platform-calxedaxgmac.o
>>  obj-$(CONFIG_VFIO_PLATFORM_AMDXGBE_RESET) += vfio-platform-amdxgbe.o
>> +obj-$(CONFIG_VFIO_PLATFORM_BCMFLEXRM_RESET) += vfio_platform_bcmflexrm.o
>> diff --git a/drivers/vfio/platform/reset/vfio_platform_bcmflexrm.c b/drivers/vfio/platform/reset/vfio_platform_bcmflexrm.c
>> new file mode 100644
>> index 0000000..a198196
>> --- /dev/null
>> +++ b/drivers/vfio/platform/reset/vfio_platform_bcmflexrm.c
>> @@ -0,0 +1,93 @@
>> +/*
>> + * Copyright (C) 2017 Broadcom
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that 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/>.
>> + */
>> +
>> +/*
>> + * This driver provides reset support for Broadcom FlexRM ring manager
>> + * to VFIO platform.
>> + */
>> +
>> +#include <linux/delay.h>
>> +#include <linux/init.h>
>> +#include <linux/io.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +
>> +#include "vfio_platform_private.h"
>> +
>> +/* FlexRM configuration */
>> +#define RING_REGS_SIZE                                       0x10000
>> +#define RING_VER_MAGIC                                       0x76303031
>> +
>> +/* Per-Ring register offsets */
>> +#define RING_VER                                     0x000
>> +#define RING_CONTROL                                 0x034
>> +#define RING_FLUSH_DONE                                      0x038
>> +
>> +/* Register RING_CONTROL fields */
>> +#define CONTROL_FLUSH_SHIFT                          5
>> +#define CONTROL_ACTIVE_SHIFT                         4
> not used

OK, I will remove this.

>> +
>> +/* Register RING_FLUSH_DONE fields */
>> +#define FLUSH_DONE_MASK                                      0x1
>> +
>> +static void vfio_platform_bcmflexrm_shutdown(void __iomem *ring)
>> +{
>> +     unsigned int timeout;
>> +
>> +     /* Disable/inactivate ring */
>> +     writel_relaxed(0x0, ring + RING_CONTROL);
>> +
>> +     /* Flush ring with timeout of 1s */
>> +     timeout = 1000;
>> +     writel_relaxed(BIT(CONTROL_FLUSH_SHIFT), ring + RING_CONTROL);
>> +     do {
>> +             if (readl_relaxed(ring + RING_FLUSH_DONE) & FLUSH_DONE_MASK)
>> +                     break;
>> +             mdelay(1);
>> +     } while (timeout--);
>> +
>> +     if (!timeout)
>> +             pr_warn("VFIO FlexRM shutdown timedout\n");
> s/timedout/timeout

OK, will fix this.

>
> vfio_platform_bcmflexrm_shutdown may also return an error that would be
> propagated to the called:
> vfio_platform_release() would then emit a dev_warn + WARN_ON. your
> choice - I know this is not done in amdxge reset function ;-) -.

Yes, its good to return error. I will try to implement this.

>
>
> Comparing to the drivers/mailbox/bcm-flexrm-mailbox.c flexrm_shutdown()
> there is one section missing commented as "Abort all in-flight
> requests". I understand there is no HW adherence of this section but I
> just want to double check that after disabling and flush the ring as
> above you guarantee there is no more DMA accesses likely to happen and
> also no platform MSI can be triggered by the HW.

We can only abort in-flight requests if we are managing device in-kernel.

For VFIO, the device is managed from user-space (DPDK) or Guest/VM
so we just need to bring HW in sane state.

>
> Otherwise looks good to me
> Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
>
> For my curiosity do you intend to do a QEMU integration of this device?

Our primary objective is to use FlexRM from user-space poll mode drivers
(DPDK).

For now, we don't plan to add support FlexRM pass-through for Guest/VM.

>
> Thanks
>
> Eric
>> +}
>> +
>> +static int vfio_platform_bcmflexrm_reset(struct vfio_platform_device *vdev)
>> +{
>> +     void __iomem *ring;
>> +     struct vfio_platform_region *reg = &vdev->regions[0];
>> +
>> +     /* Map FlexRM ring registers if not mapped */
>> +     if (!reg->ioaddr) {
>> +             reg->ioaddr = ioremap_nocache(reg->addr, reg->size);
>> +             if (!reg->ioaddr)
>> +                     return -ENOMEM;
>> +     }
>> +
>> +     /* Discover and shutdown each FlexRM ring */
>> +     for (ring = reg->ioaddr;
>> +          ring < (reg->ioaddr + reg->size); ring += RING_REGS_SIZE) {
>> +             if (readl_relaxed(ring + RING_VER) == RING_VER_MAGIC)
>> +                     vfio_platform_bcmflexrm_shutdown(ring);
>> +     }
>> +
>> +     return 0;
>> +}
>> +
>> +module_vfio_reset_handler("brcm,iproc-flexrm-mbox",
>> +                       vfio_platform_bcmflexrm_reset);
>> +
>> +MODULE_LICENSE("GPL v2");
>> +MODULE_AUTHOR("Anup Patel <anup.patel@xxxxxxxxxxxx>");
>> +MODULE_DESCRIPTION("Reset support for Broadcom FlexRM VFIO platform device");
>>

Regards,
Anup