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Date: Fri, 26 Mar 2021 17:33:17 +0100
From: Henning Schild <henning.schild@...mens.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux LED Subsystem <linux-leds@...r.kernel.org>,
Platform Driver <platform-driver-x86@...r.kernel.org>,
linux-watchdog@...r.kernel.org,
Srikanth Krishnakar <skrishnakar@...il.com>,
Jan Kiszka <jan.kiszka@...mens.com>,
Gerd Haeussler <gerd.haeussler.ext@...mens.com>,
Guenter Roeck <linux@...ck-us.net>,
Wim Van Sebroeck <wim@...ux-watchdog.org>,
Mark Gross <mgross@...ux.intel.com>,
Hans de Goede <hdegoede@...hat.com>,
Pavel Machek <pavel@....cz>
Subject: Re: [PATCH v2 2/4] leds: simatic-ipc-leds: add new driver for
Siemens Industial PCs
Am Mon, 15 Mar 2021 12:48:19 +0200
schrieb Andy Shevchenko <andy.shevchenko@...il.com>:
> On Mon, Mar 15, 2021 at 11:57 AM Henning Schild
> <henning.schild@...mens.com> wrote:
> >
> > This driver adds initial support for several devices from Siemens.
> > It is based on a platform driver introduced in an earlier commit.
>
> ...
>
> > +struct simatic_ipc_led {
> > + unsigned int value; /* mask for io and offset for mem */
>
> > + char name[32];
>
> Hmm... Dunno if LED framework defines its own constraints for the
> length of the name.
>
> > + 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" },
> >
>
> Can you use BIT() macro here? And can it be sorted by the bit order?
>
> > + {0, ""},
>
> { } is enough (no comma for terminator lines in general, and no need
> to show structure member assignments separately in particular).
>
> > +};
> > +
> > +/* the actual start will be discovered with pci, 0 is a
> > placeholder */
>
> PCI
>
> > +struct resource simatic_ipc_led_mem_res =
> > + DEFINE_RES_MEM_NAMED(0, SZ_4K, KBUILD_MODNAME);
>
> One line?
>
> ...
>
> > +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, ""},
>
> As per above.
>
> > +};
>
> ...
>
> > + struct simatic_ipc_led *led =
> > + container_of(led_cd, struct simatic_ipc_led, cdev);
> >
>
> One line?
>
> ...
>
> > + struct simatic_ipc_led *led =
> > + container_of(led_cd, struct simatic_ipc_led, cdev);
> >
>
> One line?
>
> ...
>
> > + struct simatic_ipc_led *led =
> > + container_of(led_cd, struct simatic_ipc_led, cdev);
> >
>
> Ditto.
>
>
> Btw, usually for such cases we create an inline helper
> ... to_simatic_ipc_led(...)
> {
> return container_of(...);
> }
>
> ...
>
> > +static int simatic_ipc_leds_probe(struct platform_device *pdev)
> > +{
> > + struct simatic_ipc_platform *plat;
>
> const?
>
> > + 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;
>
> Can be done directly in the definition block.
>
> > + 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);
> > + ipcled++;
> > + }
>
> This seems fishy. If you have a BE CPU it won't work the same way.
> Better:
> a) to use cpu_to_le16 / be16
> b) create this as a helper that we may move to the generic header of
> byteorder.
>
> But looking at the use of it, perhaps you rather need to redefine IO
> accessors, i.e. ioread16()/iowrite16() vs. ioread16be()/iowrite16be().
Got my hands on such a special-case device today. The comment is wrong
it talks about high and low, will fix that.
This one machine almost shares LED logic with some others. We have
those 6 bits spread over 2 consecutive bytes. For this one guy swapping
the two bytes is the shortest way to share the code.
I tried a few things, extra getters/setters, extra array defining bits
the other way around. It all ends up with way more code or conditions
in the getter/setter. So i think i will leave it like it is, clarify
that comment. And that swap16 is fine because we are on x86 only and are
basically swapping (1<<7 with 1<<15) ... where "<<" is already
endianessy.
Henning
> > + 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;
> > +
> > + /* do the final address calculation */
> > + res->start = res->start + (0xC5 << 16);
>
> Magic. As I told you this is an actual offseet in the P2SB's bar for
> GPIO registers.
> I have a question, why we can't provide a GPIO driver which is already
> in the kernel and, with use of the patch series I sent, to convert
> this all magic to GPIO LEDs as it's done for all normal cases?
>
> > + res->end += res->start;
> > +
> > + simatic_ipc_led_memory = devm_ioremap_resource(dev,
> > res);
> > + if (IS_ERR(simatic_ipc_led_memory))
> > + return PTR_ERR(simatic_ipc_led_memory);
> > +
> > + /* initialize power/watchdog LED */
> > + p = simatic_ipc_led_memory + 0x500 + 0x1D8; /*
> > PM_WDT_OUT */
> > + *p = (*p & ~1);
> > + p = simatic_ipc_led_memory + 0x500 + 0x1C0; /*
> > PM_BIOS_BOOT_N */
> > + *p = (*p | 1);
> > +
> > + break;
> > + default:
> > + return -ENODEV;
> > + }
>
> > +}
>
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