Re: [PATCH v2 2/4] leds: simatic-ipc-leds: add new driver for Siemens Industial PCs

Enrico Weigelt, metux IT consult
2021-03-18T10:26:42Z

On 15.03.21 10:57, Henning Schild wrote:

Hi,

> diff --git a/drivers/leds/simple/simatic-ipc-leds.c b/drivers/leds/simple/simatic-ipc-leds.c
> new file mode 100644
> index 000000000000..0f7e6320e10d
> --- /dev/null
> +++ b/drivers/leds/simple/simatic-ipc-leds.c
> @@ -0,0 +1,210 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Siemens SIMATIC IPC driver for LEDs
> + *
> + * Copyright (c) Siemens AG, 2018-2021
> + *
> + * Authors:
> + * Henning Schild <henning.schild@siemens.com>
> + * Jan Kiszka <jan.kiszka@siemens.com>
> + * Gerd Haeussler <gerd.haeussler.ext@siemens.com>
> + */
> +
> +#include <linux/ioport.h>
> +#include <linux/kernel.h>
> +#include <linux/leds.h>
> +#include <linux/module.h>
> +#include <linux/pci.h>
> +#include <linux/platform_data/x86/simatic-ipc-base.h>
> +#include <linux/platform_device.h>
> +#include <linux/sizes.h>
> +#include <linux/spinlock.h>
> +
> +#define SIMATIC_IPC_LED_PORT_BASE 0x404E
> +
> +struct simatic_ipc_led {
> + unsigned int value; /* mask for io and offset for mem */
> + char name[32];
> + struct led_classdev cdev;
> +};
> +
> +static struct simatic_ipc_led simatic_ipc_leds_io[] = {
> + {1 << 15, "simatic-ipc:green:" LED_FUNCTION_STATUS "-1" },
> + {1 << 7, "simatic-ipc:yellow:" LED_FUNCTION_STATUS "-1" },
> + {1 << 14, "simatic-ipc:red:" LED_FUNCTION_STATUS "-2" },
> + {1 << 6, "simatic-ipc:yellow:" LED_FUNCTION_STATUS "-2" },
> + {1 << 13, "simatic-ipc:red:" LED_FUNCTION_STATUS "-3" },
> + {1 << 5, "simatic-ipc:yellow:" LED_FUNCTION_STATUS "-3" },
> + {0, ""},
> +};

Wouldn't it be better to name them like they're labeled on the device,
as shown on page #19 of the manual, or perhaps a little bit more
generic nameing (eg. power, status, error, maint) ?

> +/* the actual start will be discovered with pci, 0 is a placeholder */
> +struct resource simatic_ipc_led_mem_res =
> + DEFINE_RES_MEM_NAMED(0, SZ_4K, KBUILD_MODNAME);
> +
> +static void *simatic_ipc_led_memory;
> +

hmm, could there *ever* be multiple instances of the driver ?

Wouldn't it be better to put this in the device priv data instead ?

> +static struct simatic_ipc_led simatic_ipc_leds_mem[] = {
> + {0x500 + 0x1A0, "simatic-ipc:red:" LED_FUNCTION_STATUS "-1"},
> + {0x500 + 0x1A8, "simatic-ipc:green:" LED_FUNCTION_STATUS "-1"},
> + {0x500 + 0x1C8, "simatic-ipc:red:" LED_FUNCTION_STATUS "-2"},
> + {0x500 + 0x1D0, "simatic-ipc:green:" LED_FUNCTION_STATUS "-2"},
> + {0x500 + 0x1E0, "simatic-ipc:red:" LED_FUNCTION_STATUS "-3"},
> + {0x500 + 0x198, "simatic-ipc:green:" LED_FUNCTION_STATUS "-3"},
> + {0, ""},
> +};
> +
> +static struct resource simatic_ipc_led_io_res =
> + DEFINE_RES_IO_NAMED(SIMATIC_IPC_LED_PORT_BASE, SZ_1, KBUILD_MODNAME);
> +
> +static DEFINE_SPINLOCK(reg_lock);

Does this protect global data structures ? If not, I'd rather put it
into the device priv data instead.

BTW: doesn't have struct led_classdev already have a lock that
can be used ? Can multiple calls to led ops (within the same device)
at the same time happen at all, or does led core already serialize
that ?

> +static void simatic_ipc_led_set_io(struct led_classdev *led_cd,
> + enum led_brightness brightness)
> +{
> + struct simatic_ipc_led *led =
> + container_of(led_cd, struct simatic_ipc_led, cdev);
> + unsigned long flags;
> + unsigned int val;
> +
> + spin_lock_irqsave(&reg_lock, flags);
> +
> + val = inw(SIMATIC_IPC_LED_PORT_BASE);
> + if (brightness == LED_OFF)
> + outw(val | led->value, SIMATIC_IPC_LED_PORT_BASE);
> + else
> + outw(val & ~led->value, SIMATIC_IPC_LED_PORT_BASE);

Don't we already have an helper for setting or clearing bits in IO
registers (that already does the read + set/clear + write at once) ?

Does that really need to be protected by lock ?
(can happen multiple calls to that func from different threads happen
at all ?)

Is the port really *always* the same, so it really can be a const ?

<snip>

> +static int simatic_ipc_leds_probe(struct platform_device *pdev)
> +{
> + struct simatic_ipc_platform *plat;
> + struct device *dev = &pdev->dev;
> + struct simatic_ipc_led *ipcled;
> + struct led_classdev *cdev;
> + struct resource *res;
> + int err, type;
> + u32 *p;
> +
> + plat = pdev->dev.platform_data;

Maybe put this into swnode ?

IIRC, the consensus is not to introduce new platform data structs
anymore, instead legacy pdata to swnode some day.

> + switch (plat->devmode) {
> + case SIMATIC_IPC_DEVICE_227D:
> + case SIMATIC_IPC_DEVICE_427E:
> + res = &simatic_ipc_led_io_res;
> + ipcled = simatic_ipc_leds_io;
> + /* the 227D is high on while 427E is low on, invert the struct
> + * we have
> + */
> + if (plat->devmode == SIMATIC_IPC_DEVICE_227D) {
> + while (ipcled->value) {
> + ipcled->value = swab16(ipcled->value);

Uff, better use explicit endian conversion macros (eg. be*_to_cpu()) for
that.

Also, I wouldn't change those global structs, instead put those data
into device priv data and make the global stuff const. You could also
use the same field for both port-io and mmap'ed variants. And adding
regmap to the equation, could use the same led ops for both. (IMHO,
the little bit of overhead by regmap shouldn't matter here)

> + ipcled++;
> + }
> + ipcled = simatic_ipc_leds_io;
> + }
> + type = IORESOURCE_IO;
> + if (!devm_request_region(dev, res->start,
> + resource_size(res),
> + KBUILD_MODNAME)) {
> + dev_err(dev,
> + "Unable to register IO resource at %pR\n",
> + res);
> + return -EBUSY;
> + }
> + break;
> + case SIMATIC_IPC_DEVICE_127E:
> + res = &simatic_ipc_led_mem_res;
> + ipcled = simatic_ipc_leds_mem;
> + type = IORESOURCE_MEM;
> +
> + /* get GPIO base from PCI */
> + res->start = simatic_ipc_get_membase0(PCI_DEVFN(13, 0));
> + if (res->start == 0)
> + return -ENODEV;

Where does that device actually sit on ? Some generic card ? Some ASIC
or FPGA ?

It seems this driver is instantiated by another one, which already knows
what device we're actually dealing with (as it sets plat->devmode).
Why not letting that parent device also tell the io resource to this
driver ?

> + while (ipcled->value) {
> + cdev = &ipcled->cdev;
> + cdev->brightness_set = simatic_ipc_led_set_io;
> + cdev->brightness_get = simatic_ipc_led_get_io;
> + if (type == IORESOURCE_MEM) {
> + cdev->brightness_set = simatic_ipc_led_set_mem;
> + cdev->brightness_get = simatic_ipc_led_get_mem;
> + }

Why not if/else ?

> + cdev->max_brightness = LED_ON;
> + cdev->name = ipcled->name;
> +
> + err = devm_led_classdev_register(dev, cdev);
> + if (err < 0)
> + return err;
> + ipcled++;
> + }
> +
> + return 0;
> +}
> +
> +static struct platform_driver led_driver = {

Why not calling it simatic_ipc_led_driver ?

> + .probe = simatic_ipc_leds_probe,
> + .driver = {
> + .name = KBUILD_MODNAME,
> + },
> +};
> +
> +module_platform_driver(led_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_ALIAS("platform:" KBUILD_MODNAME);
> +MODULE_AUTHOR("Henning Schild <henning.schild@siemens.com>");
>

--mtx

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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@metux.net -- +49-151-27565287