Re: [PATCH v2 1/4] platform/x86: simatic-ipc: add main driver for Siemens devices

[Andy Shevchenko <andy.shevchenko@gmail.com>]

On Mon, Mar 15, 2021 at 12:02 PM Henning Schild
<henning.schild@siemens.com> wrote:
>
> This mainly implements detection of these devices and will allow
> secondary drivers to work on such machines.
>
> The identification is DMI-based with a vendor specific way to tell them
> apart in a reliable way.
>
> Drivers for LEDs and Watchdogs will follow to make use of that platform
> detection.

...

> +static int register_platform_devices(u32 station_id)
> +{
> +       u8 ledmode = SIMATIC_IPC_DEVICE_NONE;
> +       u8 wdtmode = SIMATIC_IPC_DEVICE_NONE;
> +       int i;
> +
> +       platform_data.devmode = SIMATIC_IPC_DEVICE_NONE;
> +
> +       for (i = 0; i < ARRAY_SIZE(device_modes); i++) {
> +               if (device_modes[i].station_id == station_id) {
> +                       ledmode = device_modes[i].led_mode;
> +                       wdtmode = device_modes[i].wdt_mode;
> +                       break;
> +               }
> +       }
> +
> +       if (ledmode != SIMATIC_IPC_DEVICE_NONE) {
> +               platform_data.devmode = ledmode;
> +               ipc_led_platform_device =
> +                       platform_device_register_data(NULL,
> +                               KBUILD_MODNAME "_leds", PLATFORM_DEVID_NONE,
> +                               &platform_data,
> +                               sizeof(struct simatic_ipc_platform));
> +               if (IS_ERR(ipc_led_platform_device))
> +                       return PTR_ERR(ipc_led_platform_device);
> +
> +               pr_debug("device=%s created\n",
> +                        ipc_led_platform_device->name);
> +       }
> +
> +       if (wdtmode != SIMATIC_IPC_DEVICE_NONE) {
> +               platform_data.devmode = wdtmode;
> +               ipc_wdt_platform_device =
> +                       platform_device_register_data(NULL,
> +                               KBUILD_MODNAME "_wdt", PLATFORM_DEVID_NONE,
> +                               &platform_data,
> +                               sizeof(struct simatic_ipc_platform));
> +               if (IS_ERR(ipc_wdt_platform_device))
> +                       return PTR_ERR(ipc_wdt_platform_device);
> +
> +               pr_debug("device=%s created\n",
> +                        ipc_wdt_platform_device->name);
> +       }
> +
> +       if (ledmode == SIMATIC_IPC_DEVICE_NONE &&
> +           wdtmode == SIMATIC_IPC_DEVICE_NONE) {
> +               pr_warn("unsupported IPC detected, station id=%08x\n",
> +                       station_id);
> +               return -EINVAL;
> +       }
> +
> +       return 0;
> +}

Why not use MFD here?

...

> +/*
> + * Get membase address from PCI, used in leds and wdt modul. Here we read
> + * the bar0. The final address calculation is done in the appropriate modules
> + */

No blank line here.

I would add FIXME or REVISIT here to point out that this should be
deduplicated in the future.

> +u32 simatic_ipc_get_membase0(unsigned int p2sb)
> +{
> +       struct pci_bus *bus;
> +       u32 bar0 = 0;
> +
> +       /*
> +        * The GPIO memory is bar0 of the hidden P2SB device. Unhide the device

No, it's not a GPIO's bar. It's P2SB's one. GPIO resides in that bar somewhere.

> +        * to have a quick look at it, before we hide it again.
> +        * Also grab the pci rescan lock so that device does not get discovered
> +        * and remapped while it is visible.
> +        * This code is inspired by drivers/mfd/lpc_ich.c
> +        */
> +       bus = pci_find_bus(0, 0);
> +       pci_lock_rescan_remove();
> +       pci_bus_write_config_byte(bus, p2sb, 0xE1, 0x0);
> +       pci_bus_read_config_dword(bus, p2sb, PCI_BASE_ADDRESS_0, &bar0);
> +
> +       bar0 &= ~0xf;
> +       pci_bus_write_config_byte(bus, p2sb, 0xE1, 0x1);
> +       pci_unlock_rescan_remove();
> +
> +       return bar0;
> +}
> +EXPORT_SYMBOL(simatic_ipc_get_membase0);

...

> +static inline u32 simatic_ipc_get_station_id(u8 *data, int max_len)
> +{
> +       u32 station_id = SIMATIC_IPC_INVALID_STATION_ID;
> +       int i;

Reversed xmas tree order, please.

> +       struct {
> +               u8      type;           /* type (0xff = binary) */
> +               u8      len;            /* len of data entry */
> +               u8      reserved[3];
> +               u32     station_id;     /* station id (LE) */

> +       } __packed
> +       *data_entry = (void *)data + sizeof(struct dmi_header);

Can be one line.

> +       /* find 4th entry in OEM data */
> +       for (i = 0; i < 3; i++)

3 is magic!

> +               data_entry = (void *)((u8 *)(data_entry) + data_entry->len);
> +
> +       /* decode station id */
> +       if (data_entry && (u8 *)data_entry < data + max_len &&
> +           data_entry->type == 0xff && data_entry->len == 9)
> +               station_id = le32_to_cpu(data_entry->station_id);
> +
> +       return station_id;
> +}

-- 
With Best Regards,
Andy Shevchenko