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

Hans de Goede
2021-03-17T20:04:02Z

Hi,

On 3/17/21 8:13 PM, Henning Schild wrote:
> Am Mon, 15 Mar 2021 12:31:11 +0200
> schrieb 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?
>
> Never had a close look at mfd to be honest. I might
>
> With the custom dmi matching on 129 being part of the header, and the
> p2sb unhide moving out as well ... that first driver ends up being not
> too valuable indeed
>
> It just identifies the box and tells subsequent drivers which one it
> is, which watchdog and LED path to take. Moving the knowledge of which
> box has which LED/watchdog into the respective drivers seems to be the
> better way to go.
>
> So we would end up with a LED and a watchdog driver both
> MODULE_ALIAS("dmi:*:svnSIEMENSAG:*");
> and doing the identification with the inline dmi from that header,
> doing p2sb with the support to come ... possibly a "//TODO\ninline" in
> the meantime.
>
> So no "main platform" driver anymore, but still central platform
> headers.
>
> Not sure how this sounds, but i think making that change should be
> possible. And that is what i will try and go for in v3.

Dropping the main drivers/platform/x86 driver sounds good to me,
I was already wondering a bit about its function since it just
instantiates devs to which the other ones bind to then instantiate
more devs (in the LED case).

Regards,

Hans

>> ...
>>
>>> +/*
>>> + * 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;
>>> +}
>>
>