Re: [PATCH v6] drivers/misc: Add Aspeed LPC control driver

[Joel Stanley]

On Fri, Feb 17, 2017 at 1:58 PM, Cyril Bur <cyrilbur@xxxxxxxxx> wrote:
> In order to manage server systems, there is typically another processor
> known as a BMC (Baseboard Management Controller) which is responsible
> for powering the server and other various elements, sometimes fans,
> often the system flash.
>
> The Aspeed BMC family which is what is used on OpenPOWER machines and a
> number of x86 as well is typically connected to the host via an LPC
> (Low Pin Count) bus (among others).
>
> The LPC bus is an ISA bus on steroids. It's generally used by the
> BMC chip to provide the host with access to the system flash (via MEM/FW
> cycles) that contains the BIOS or other host firmware along with a
> number of SuperIO-style IOs (via IO space) such as UARTs, IPMI
> controllers.
>
> On the BMC chip side, this is all configured via a bunch of registers
> whose content is related to a given policy of what devices are exposed
> at a per system level, which is system/vendor specific, so we don't want
> to bolt that into the BMC kernel. This started with a need to provide
> something nicer than /dev/mem for user space to configure these things.
>
> One important aspect of the configuration is how the MEM/FW space is
> exposed to the host (ie, the x86 or POWER). Some registers in that
> bridge can define a window remapping all or portion of the LPC MEM/FW
> space to a portion of the BMC internal bus, with no specific limits
> imposed in HW.
>
> I think it makes sense to ensure that this window is configured by a
> kernel driver that can apply some serious sanity checks on what it is
> configured to map.
>
> In practice, user space wants to control this by flipping the mapping
> between essentially two types of portions of the BMC address space:
>
>    - The flash space. This is a region of the BMC MMIO space that
> more/less directly maps the system flash (at least for reads, writes
> are somewhat more complicated).
>
>    - One (or more) reserved area(s) of the BMC physical memory.
>
> The latter is needed for a number of things, such as avoiding letting
> the host manipulate the innards of the BMC flash controller via some
> evil backdoor, we want to do flash updates by routing the window to a
> portion of memory (under control of a mailbox protocol via some
> separate set of registers) which the host can use to write new data in
> bulk and then request the BMC to flash it. There are other uses, such
> as allowing the host to boot from an in-memory flash image rather than
> the one in flash (very handy for continuous integration and test, the
> BMC can just download new images).
>
> It is important to note that due to the way the Aspeed chip lets the
> kernel configure the mapping between host LPC addresses and BMC ram
> addresses the offset within the window must be a multiple of size.
> Not doing so will fragment the accessible space rather than simply
> moving 'zero' upwards. This is caused by the nature of HICR8 being a
> mask and the way host LPC addresses are translated.
>
> Signed-off-by: Cyril Bur <cyrilbur@xxxxxxxxx>
> ---
> v2:
>    Removed unused functions
>    Removed use of access_ok()
>    All input is evil
>    Reworked the interface as per Benjamin Herrenschmidts vision
> v3:
>    Removed 'default y' from Kconfig
>    Reordered ioctl() struct fields
>    Reworeded some comments
> v4:
>    Reorder ioctl() struct fields (again)
> v5:
>    Style cleanups
>    Use of_address_to_resource()
>    Document ioctl structure fields
> v6:
>    Check and fail ioctl() if flags field non-zero

Woot!

Reviewed-by: Joel Stanley <joel@xxxxxxxxx>

>
>  drivers/misc/Kconfig                 |   8 ++
>  drivers/misc/Makefile                |   1 +
>  drivers/misc/aspeed-lpc-ctrl.c       | 267 +++++++++++++++++++++++++++++++++++
>  include/uapi/linux/aspeed-lpc-ctrl.h |  60 ++++++++
>  4 files changed, 336 insertions(+)
>  create mode 100644 drivers/misc/aspeed-lpc-ctrl.c
>  create mode 100644 include/uapi/linux/aspeed-lpc-ctrl.h
>
> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index 64971baf11fa..7dc4c369012f 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -766,6 +766,14 @@ config PANEL_BOOT_MESSAGE
>           An empty message will only clear the display at driver init time. Any other
>           printf()-formatted message is valid with newline and escape codes.
>
> +config ASPEED_LPC_CTRL
> +       depends on (ARCH_ASPEED || COMPILE_TEST) && REGMAP && MFD_SYSCON
> +       tristate "Aspeed ast2400/2500 HOST LPC to BMC bridge control"
> +       ---help---
> +         Control Aspeed ast2400/2500 HOST LPC to BMC mappings through
> +         ioctl()s, the driver also provides a read/write interface to a BMC ram
> +         region where the host LPC read/write region can be buffered.
> +
>  source "drivers/misc/c2port/Kconfig"
>  source "drivers/misc/eeprom/Kconfig"
>  source "drivers/misc/cb710/Kconfig"
> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> index 31983366090a..de1925a9c80b 100644
> --- a/drivers/misc/Makefile
> +++ b/drivers/misc/Makefile
> @@ -53,6 +53,7 @@ obj-$(CONFIG_ECHO)            += echo/
>  obj-$(CONFIG_VEXPRESS_SYSCFG)  += vexpress-syscfg.o
>  obj-$(CONFIG_CXL_BASE)         += cxl/
>  obj-$(CONFIG_PANEL)             += panel.o
> +obj-$(CONFIG_ASPEED_LPC_CTRL)  += aspeed-lpc-ctrl.o
>
>  lkdtm-$(CONFIG_LKDTM)          += lkdtm_core.o
>  lkdtm-$(CONFIG_LKDTM)          += lkdtm_bugs.o
> diff --git a/drivers/misc/aspeed-lpc-ctrl.c b/drivers/misc/aspeed-lpc-ctrl.c
> new file mode 100644
> index 000000000000..f6acbe1d9378
> --- /dev/null
> +++ b/drivers/misc/aspeed-lpc-ctrl.c
> @@ -0,0 +1,267 @@
> +/*
> + * Copyright 2017 IBM Corporation
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#include <linux/mfd/syscon.h>
> +#include <linux/miscdevice.h>
> +#include <linux/mm.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/platform_device.h>
> +#include <linux/poll.h>
> +#include <linux/regmap.h>
> +
> +#include <linux/aspeed-lpc-ctrl.h>
> +
> +#define DEVICE_NAME    "aspeed-lpc-ctrl"
> +
> +#define HICR7 0x8
> +#define HICR8 0xc
> +
> +struct aspeed_lpc_ctrl {
> +       struct miscdevice       miscdev;
> +       struct regmap           *regmap;
> +       phys_addr_t             mem_base;
> +       resource_size_t         mem_size;
> +       u32             pnor_size;
> +       u32             pnor_base;
> +};
> +
> +static struct aspeed_lpc_ctrl *file_aspeed_lpc_ctrl(struct file *file)
> +{
> +       return container_of(file->private_data, struct aspeed_lpc_ctrl,
> +                       miscdev);
> +}
> +
> +static int aspeed_lpc_ctrl_mmap(struct file *file, struct vm_area_struct *vma)
> +{
> +       struct aspeed_lpc_ctrl *lpc_ctrl = file_aspeed_lpc_ctrl(file);
> +       unsigned long vsize = vma->vm_end - vma->vm_start;
> +       pgprot_t prot = vma->vm_page_prot;
> +
> +       if (vma->vm_pgoff + vsize > lpc_ctrl->mem_base + lpc_ctrl->mem_size)
> +               return -EINVAL;
> +
> +       /* ast2400/2500 AHB accesses are not cache coherent */
> +       prot = pgprot_dmacoherent(prot);
> +
> +       if (remap_pfn_range(vma, vma->vm_start,
> +               (lpc_ctrl->mem_base >> PAGE_SHIFT) + vma->vm_pgoff,
> +               vsize, prot))
> +               return -EAGAIN;
> +
> +       return 0;
> +}
> +
> +static long aspeed_lpc_ctrl_ioctl(struct file *file, unsigned int cmd,
> +               unsigned long param)
> +{
> +       struct aspeed_lpc_ctrl *lpc_ctrl = file_aspeed_lpc_ctrl(file);
> +       void __user *p = (void __user *)param;
> +       struct aspeed_lpc_ctrl_mapping map;
> +       u32 addr;
> +       u32 size;
> +       long rc;
> +
> +       if (copy_from_user(&map, p, sizeof(map)))
> +               return -EFAULT;
> +
> +       if (map.flags != 0)
> +               return -EINVAL;
> +
> +       switch (cmd) {
> +       case ASPEED_LPC_CTRL_IOCTL_GET_SIZE:
> +               /* The flash windows don't report their size */
> +               if (map.window_type != ASPEED_LPC_CTRL_WINDOW_MEMORY)
> +                       return -EINVAL;
> +
> +               /* Support more than one window id in the future */
> +               if (map.window_id != 0)
> +                       return -EINVAL;
> +
> +               map.size = lpc_ctrl->mem_size;
> +
> +               return copy_to_user(p, &map, sizeof(map)) ? -EFAULT : 0;
> +       case ASPEED_LPC_CTRL_IOCTL_MAP:
> +
> +               /*
> +                * The top half of HICR7 is the MSB of the BMC address of the
> +                * mapping.
> +                * The bottom half of HICR7 is the MSB of the HOST LPC
> +                * firmware space address of the mapping.
> +                *
> +                * The 1 bits in the top of half of HICR8 represent the bits
> +                * (in the requested address) that should be ignored and
> +                * replaced with those from the top half of HICR7.
> +                * The 1 bits in the bottom half of HICR8 represent the bits
> +                * (in the requested address) that should be kept and pass
> +                * into the BMC address space.
> +                */
> +
> +               /*
> +                * It doesn't make sense to talk about a size or offset with
> +                * low 16 bits set. Both HICR7 and HICR8 talk about the top 16
> +                * bits of addresses and sizes.
> +                */
> +
> +               if ((map.size & 0x0000ffff) || (map.offset & 0x0000ffff))
> +                       return -EINVAL;
> +
> +               /*
> +                * Because of the way the masks work in HICR8 offset has to
> +                * be a multiple of size.
> +                */
> +               if (map.offset & (map.size - 1))
> +                       return -EINVAL;
> +
> +               if (map.window_type == ASPEED_LPC_CTRL_WINDOW_FLASH) {
> +                       addr = lpc_ctrl->pnor_base;
> +                       size = lpc_ctrl->pnor_size;
> +               } else if (map.window_type == ASPEED_LPC_CTRL_WINDOW_MEMORY) {
> +                       addr = lpc_ctrl->mem_base;
> +                       size = lpc_ctrl->mem_size;
> +               } else {
> +                       return -EINVAL;
> +               }
> +
> +               /* Check overflow first! */
> +               if (map.offset + map.size < map.offset ||
> +                       map.offset + map.size > size)
> +                       return -EINVAL;
> +
> +               if (map.size == 0 || map.size > size)
> +                       return -EINVAL;
> +
> +               addr += map.offset;
> +
> +               /*
> +                * addr (host lpc address) is safe regardless of values. This
> +                * simply changes the address the host has to request on its
> +                * side of the LPC bus. This cannot impact the hosts own
> +                * memory space by surprise as LPC specific accessors are
> +                * required. The only strange thing that could be done is
> +                * setting the lower 16 bits but the shift takes care of that.
> +                */
> +
> +               rc = regmap_write(lpc_ctrl->regmap, HICR7,
> +                               (addr | (map.addr >> 16)));
> +               if (rc)
> +                       return rc;
> +
> +               return regmap_write(lpc_ctrl->regmap, HICR8,
> +                       (~(map.size - 1)) | ((map.size >> 16) - 1));
> +       }
> +
> +       return -EINVAL;
> +}
> +
> +static const struct file_operations aspeed_lpc_ctrl_fops = {
> +       .owner          = THIS_MODULE,
> +       .mmap           = aspeed_lpc_ctrl_mmap,
> +       .unlocked_ioctl = aspeed_lpc_ctrl_ioctl,
> +};
> +
> +static int aspeed_lpc_ctrl_probe(struct platform_device *pdev)
> +{
> +       struct aspeed_lpc_ctrl *lpc_ctrl;
> +       struct device_node *node;
> +       struct resource resm;
> +       struct device *dev;
> +       int rc;
> +
> +       dev = &pdev->dev;
> +
> +       lpc_ctrl = devm_kzalloc(dev, sizeof(*lpc_ctrl), GFP_KERNEL);
> +       if (!lpc_ctrl)
> +               return -ENOMEM;
> +
> +       node = of_parse_phandle(dev->of_node, "flash", 0);
> +       if (!node) {
> +               dev_err(dev, "Didn't find host pnor flash node\n");
> +               return -ENODEV;
> +       }
> +
> +       rc = of_address_to_resource(node, 1, &resm);
> +       of_node_put(node);
> +       if (rc) {
> +               dev_err(dev, "Couldn't address to resource for flash\n");
> +               return rc;
> +       }
> +
> +       lpc_ctrl->pnor_size = resource_size(&resm);
> +       lpc_ctrl->pnor_base = resm.start;
> +
> +       dev_set_drvdata(&pdev->dev, lpc_ctrl);
> +
> +       node = of_parse_phandle(dev->of_node, "memory-region", 0);
> +       if (!node) {
> +               dev_err(dev, "Didn't find reserved memory\n");
> +               return -EINVAL;
> +       }
> +
> +       rc = of_address_to_resource(node, 0, &resm);
> +       of_node_put(node);
> +       if (rc) {
> +               dev_err(dev, "Couldn't address to resource for reserved memory\n");
> +               return -ENOMEM;
> +       }
> +
> +       lpc_ctrl->mem_size = resource_size(&resm);
> +       lpc_ctrl->mem_base = resm.start;
> +
> +       lpc_ctrl->regmap = syscon_node_to_regmap(
> +                       pdev->dev.parent->of_node);
> +       if (IS_ERR(lpc_ctrl->regmap)) {
> +               dev_err(dev, "Couldn't get regmap\n");
> +               return -ENODEV;
> +       }
> +
> +       lpc_ctrl->miscdev.minor = MISC_DYNAMIC_MINOR;
> +       lpc_ctrl->miscdev.name = DEVICE_NAME;
> +       lpc_ctrl->miscdev.fops = &aspeed_lpc_ctrl_fops;
> +       lpc_ctrl->miscdev.parent = dev;
> +       rc = misc_register(&lpc_ctrl->miscdev);
> +       if (rc)
> +               dev_err(dev, "Unable to register device\n");
> +       else
> +               dev_info(dev, "Loaded at 0x%08x (0x%08x)\n",
> +                       lpc_ctrl->mem_base, lpc_ctrl->mem_size);
> +
> +       return rc;
> +}
> +
> +static int aspeed_lpc_ctrl_remove(struct platform_device *pdev)
> +{
> +       struct aspeed_lpc_ctrl *lpc_ctrl = dev_get_drvdata(&pdev->dev);
> +
> +       misc_deregister(&lpc_ctrl->miscdev);
> +
> +       return 0;
> +}
> +
> +static const struct of_device_id aspeed_lpc_ctrl_match[] = {
> +       { .compatible = "aspeed,ast2400-lpc-ctrl" },
> +       { .compatible = "aspeed,ast2500-lpc-ctrl" },
> +       { },
> +};
> +
> +static struct platform_driver aspeed_lpc_ctrl_driver = {
> +       .driver = {
> +               .name           = DEVICE_NAME,
> +               .of_match_table = aspeed_lpc_ctrl_match,
> +       },
> +       .probe = aspeed_lpc_ctrl_probe,
> +       .remove = aspeed_lpc_ctrl_remove,
> +};
> +
> +module_platform_driver(aspeed_lpc_ctrl_driver);
> +
> +MODULE_DEVICE_TABLE(of, aspeed_lpc_ctrl_match);
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Cyril Bur <cyrilbur@xxxxxxxxx>");
> +MODULE_DESCRIPTION("Control for aspeed 2400/2500 LPC HOST to BMC mappings");
> diff --git a/include/uapi/linux/aspeed-lpc-ctrl.h b/include/uapi/linux/aspeed-lpc-ctrl.h
> new file mode 100644
> index 000000000000..f96fa995a3f0
> --- /dev/null
> +++ b/include/uapi/linux/aspeed-lpc-ctrl.h
> @@ -0,0 +1,60 @@
> +/*
> + * Copyright 2017 IBM Corp.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#ifndef _UAPI_LINUX_ASPEED_LPC_CTRL_H
> +#define _UAPI_LINUX_ASPEED_LPC_CTRL_H
> +
> +#include <linux/ioctl.h>
> +
> +/* Window types */
> +#define ASPEED_LPC_CTRL_WINDOW_FLASH   1
> +#define ASPEED_LPC_CTRL_WINDOW_MEMORY  2
> +
> +/*
> + * This driver provides a window for the host to access a BMC resource
> + * across the BMC <-> Host LPC bus.
> + *
> + * window_type: The BMC resource that the host will access through the
> + * window. BMC flash and BMC RAM.
> + *
> + * window_id: For each window type there may be multiple windows,
> + * these are referenced by ID.
> + *
> + * flags: Reserved for future use, this field is expected to be
> + * zeroed.
> + *
> + * addr: Address on the host LPC bus that the specified window should
> + * be mapped. This address must be power of two aligned.
> + *
> + * offset: Offset into the BMC window that should be mapped to the
> + * host (at addr). This must be a multiple of size.
> + *
> + * size: The size of the mapping. The smallest possible size is 64K.
> + * This must be power of two aligned.
> + *
> + */
> +
> +struct aspeed_lpc_ctrl_mapping {
> +       __u8    window_type;
> +       __u8    window_id;
> +       __u16   flags;
> +       __u32   addr;
> +       __u32   offset;
> +       __u32   size;
> +};
> +
> +#define __ASPEED_LPC_CTRL_IOCTL_MAGIC  0xb2
> +
> +#define ASPEED_LPC_CTRL_IOCTL_GET_SIZE _IOWR(__ASPEED_LPC_CTRL_IOCTL_MAGIC, \
> +               0x00, struct aspeed_lpc_ctrl_mapping)
> +
> +#define ASPEED_LPC_CTRL_IOCTL_MAP      _IOW(__ASPEED_LPC_CTRL_IOCTL_MAGIC, \
> +               0x01, struct aspeed_lpc_ctrl_mapping)
> +
> +#endif /* _UAPI_LINUX_ASPEED_LPC_CTRL_H */
> --
> 2.11.1
>