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Message-ID:
<PH0PR18MB4425E0F2E295B8EAEDCD942CD9882@PH0PR18MB4425.namprd18.prod.outlook.com>
Date: Fri, 23 Aug 2024 13:06:34 +0000
From: Shijith Thotton <sthotton@...vell.com>
To: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
CC: "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
"Jonathan.Cameron@...wei.com"
<Jonathan.Cameron@...wei.com>,
LKML <linux-kernel@...r.kernel.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"Rafael J. Wysocki"
<rafael@...nel.org>,
"scott@...amperecomputing.com"
<scott@...amperecomputing.com>,
Jerin Jacob <jerinj@...vell.com>,
Srujana
Challa <schalla@...vell.com>,
Vamsi Krishna Attunuru <vattunuru@...vell.com>
Subject: Re: [PATCH v2] PCI: hotplug: Add OCTEON PCI hotplug controller driver
>> This patch introduces a PCI hotplug controller driver for the OCTEON
>> PCIe device, a multi-function PCIe device where the first function acts
>> as a hotplug controller. It is equipped with MSI-x interrupts to notify
>> the host of hotplug events from the OCTEON firmware.
>>
>> The driver facilitates the hotplugging of non-controller functions
>> within the same device. During probe, non-controller functions are
>> removed and registered as PCI hotplug slots. The slots are added back
>> only upon request from the device firmware. The driver also allows the
>> enabling and disabling of the slots via sysfs slot entries, provided by
>> the PCI hotplug framework.
>>
>> Signed-off-by: Shijith Thotton <sthotton@...vell.com>
>> Co-developed-by: Vamsi Attunuru <vattunuru@...vell.com>
>> Signed-off-by: Vamsi Attunuru <vattunuru@...vell.com>
>> ---
>>
>> This patch introduces a PCI hotplug controller driver for OCTEON PCIe hotplug
>> controller. The OCTEON PCIe device is a multi-function device where the first
>> function acts as a PCI hotplug controller.
>>
>> +--------------------------------+
>> | Root Port |
>> +--------------------------------+
>> |
>> PCIe
>> |
>> +---------------------------------------------------------------+
>> | OCTEON PCIe Multifunction Device |
>> +---------------------------------------------------------------+
>> | | | |
>> | | | |
>> +---------------------+ +----------------+ +-----+ +----------------+
>> | Function 0 | | Function 1 | | ... | | Function 7 |
>> | (Hotplug controller)| | (Hotplug slot) | | | | (Hotplug slot) |
>> +---------------------+ +----------------+ +-----+ +----------------+
>> |
>> |
>> +-------------------------+
>> | Controller Firmware |
>> +-------------------------+
>>
>> The hotplug controller driver facilitates the hotplugging of non-controller
>> functions in the same device. During the probe of the driver, the non-
>controller
>> function are removed and registered as PCI hotplug slots. They are added
>back
>> only upon request from the device firmware. The driver also allows the user
>to
>> enable/disable the functions using sysfs slot entries provided by PCI hotplug
>> framework.
>>
>> This solution adopts a hardware + software approach for several reasons:
>>
>> 1. To reduce hardware implementation cost. Supporting complete hotplug
>> capability within the card would require a PCI switch implemented within.
>>
>> 2. In the multi-function device, non-controller functions can act as emulated
>> devices. The firmware can dynamically enable or disable them at runtime.
>>
>> 3. Not all root ports support PCI hotplug. This approach provides greater
>> flexibility and compatibility across different hardware configurations.
>>
>> The hotplug controller function is lightweight and is equipped with MSI-x
>> interrupts to notify the host about hotplug events. Upon receiving an
>> interrupt, the hotplug register is read, and the required function is enabled
>> or disabled.
>>
>> This driver will be beneficial for managing PCI hotplug events on the OCTEON
>> PCIe device without requiring complex hardware solutions.
>>
>> Changes in v2:
>> - Added missing include files.
>> - Used dev_err_probe() for error handling.
>> - Used guard() for mutex locking.
>> - Splited cleanup actions and added per-slot cleanup action.
>> - Fixed coding style issues.
>> - Added co-developed-by tag.
>>
>> MAINTAINERS | 6 +
>> drivers/pci/hotplug/Kconfig | 10 +
>> drivers/pci/hotplug/Makefile | 1 +
>> drivers/pci/hotplug/octep_hp.c | 412
>+++++++++++++++++++++++++++++++++
>> 4 files changed, 429 insertions(+)
>> create mode 100644 drivers/pci/hotplug/octep_hp.c
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 42decde38320..7b5a618eed1c 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -13677,6 +13677,12 @@ R: schalla@...vell.com
>> R: vattunuru@...vell.com
>> F: drivers/vdpa/octeon_ep/
>>
>> +MARVELL OCTEON HOTPLUG CONTROLLER DRIVER
>> +R: Shijith Thotton <sthotton@...vell.com>
>> +R: Vamsi Attunuru <vattunuru@...vell.com>
>> +S: Supported
>> +F: drivers/pci/hotplug/octep_hp.c
>> +
>> MATROX FRAMEBUFFER DRIVER
>> L: linux-fbdev@...r.kernel.org
>> S: Orphan
>> diff --git a/drivers/pci/hotplug/Kconfig b/drivers/pci/hotplug/Kconfig
>> index 1472aef0fb81..2e38fd25f7ef 100644
>> --- a/drivers/pci/hotplug/Kconfig
>> +++ b/drivers/pci/hotplug/Kconfig
>> @@ -173,4 +173,14 @@ config HOTPLUG_PCI_S390
>>
>> When in doubt, say Y.
>>
>> +config HOTPLUG_PCI_OCTEONEP
>> + bool "OCTEON PCI device Hotplug controller driver"
>> + depends on HOTPLUG_PCI
>> + help
>> + Say Y here if you have an OCTEON PCIe device with a hotplug
>> + controller. This driver enables the non-controller functions of the
>> + device to be registered as hotplug slots.
>> +
>> + When in doubt, say N.
>> +
>> endif # HOTPLUG_PCI
>> diff --git a/drivers/pci/hotplug/Makefile b/drivers/pci/hotplug/Makefile
>> index 240c99517d5e..40aaf31fe338 100644
>> --- a/drivers/pci/hotplug/Makefile
>> +++ b/drivers/pci/hotplug/Makefile
>> @@ -20,6 +20,7 @@ obj-$(CONFIG_HOTPLUG_PCI_RPA) +=
>rpaphp.o
>> obj-$(CONFIG_HOTPLUG_PCI_RPA_DLPAR) += rpadlpar_io.o
>> obj-$(CONFIG_HOTPLUG_PCI_ACPI) += acpiphp.o
>> obj-$(CONFIG_HOTPLUG_PCI_S390) += s390_pci_hpc.o
>> +obj-$(CONFIG_HOTPLUG_PCI_OCTEONEP) += octep_hp.o
>>
>> # acpiphp_ibm extends acpiphp, so should be linked afterwards.
>>
>> diff --git a/drivers/pci/hotplug/octep_hp.c b/drivers/pci/hotplug/octep_hp.c
>> new file mode 100644
>> index 000000000000..3ac90ffff564
>> --- /dev/null
>> +++ b/drivers/pci/hotplug/octep_hp.c
>> @@ -0,0 +1,412 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/* Copyright (C) 2024 Marvell. */
>> +
>> +#include <linux/cleanup.h>
>> +#include <linux/container_of.h>
>> +#include <linux/delay.h>
>> +#include <linux/dev_printk.h>
>> +#include <linux/init.h>
>> +#include <linux/interrupt.h>
>> +#include <linux/io-64-nonatomic-lo-hi.h>
>> +#include <linux/kernel.h>
>> +#include <linux/list.h>
>> +#include <linux/module.h>
>> +#include <linux/mutex.h>
>> +#include <linux/pci.h>
>> +#include <linux/pci_hotplug.h>
>> +#include <linux/slab.h>
>> +#include <linux/spinlock.h>
>> +#include <linux/workqueue.h>
>> +
>> +#define OCTEP_HP_INTR_OFFSET(x) (0x20400 + ((x) << 4))
>> +#define OCTEP_HP_INTR_VECTOR(x) (16 + (x))
>> +#define OCTEP_HP_DRV_NAME "octep_hp"
>> +
>> +/*
>> + * Type of MSI-X interrupts.
>> + * The macros OCTEP_HP_INTR_VECTOR and OCTEP_HP_INTR_OFFSET are
>used to
>> + * generate the vector and offset for an interrupt type.
>> + */
>> +enum octep_hp_intr_type {
>> + OCTEP_HP_INTR_INVALID = -1,
>> + OCTEP_HP_INTR_ENA,
>> + OCTEP_HP_INTR_DIS,
>
>Making these numbers explicit (since they cannot be just any numbers) fell
>through cracks.
>
The functionality of the code is good since the enum values are automatically
sequential. The values we need for the interrupt types are OCTEP_HP_INTR_ENA as
0 and OCTEP_HP_INTR_DIS as 1. I will include the explicit assignments in v3.
Thanks,
Shijith
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