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SubjectRe: [PATCH v2 1/3] mfd: upboard: Add UP2 platform controller driver
On Sat, 20 Oct 2018, Andy Shevchenko wrote:

> On Fri, Oct 19, 2018 at 8:26 PM Dan O'Donovan <dan@emutex.com> wrote:
> >
> > From: Javier Arteaga <javier@emutex.com>
> >
> > UP Squared (UP2) is a x86 SBC from AAEON based on Intel Apollo Lake. It
> > features a MAX 10 FPGA that routes lines from both SoC and on-board
> > devices to two I/O headers:
> >
> > +------------------------+
> > | 40-pin RPi-like header |
> > +------| (HAT) |
> > | +------------------------+
> > +-------+ +--------+
> > | | | | +------------------------+
> > | SoC |----| FPGA |-----| Custom UP2 pin header |
> > | | | | | (EXHAT) |
> > +-------+ +--------+ +------------------------+
> > |
> > +------* On-board devices: LED, VLS...
> >
> > This is intended to enable vendor-specific applications to customize I/O
> > header pinout, as well as include low-latency functionality. It also
> > performs voltage level translation between the SoC (1.8V) and HAT header
> > (3.3V).
> >
> > Out of the box, this block implements a platform controller with a
> > GPIO-bitbanged control interface. It's enumerated by ACPI and provides
> > registers to control:
> >
> > - Configuration of all FPGA-routed header lines. These can be driven
> > SoC-to-header, header-to-SoC or set in high impedance.
> >
> > - On-board LEDs and enable lines for other platform devices.
> >
> > Add core support for this platform controller as a MFD device, exposing
> > these registers as a regmap.
>
> Can we see a link to or an excerpt of ACPI table for this device?
>
> > +#define set_clear(u, x) gpiod_set_value((u)->clear_gpio, (x))
> > +#define set_strobe(u, x) gpiod_set_value((u)->strobe_gpio, (x))
> > +#define set_datain(u, x) gpiod_set_value((u)->datain_gpio, (x))
> > +#define get_dataout(u) gpiod_get_value((u)->dataout_gpio)
>
> I think these macros don't bring much value. (Up to you and Lee to decide)

I agree.

In fact I think they only serve to obfuscate instead of clarify.

[...]

> > + set_strobe(ddata, 0);
> > + set_strobe(ddata, 1);
> > + *val |= get_dataout(ddata) << i;
> > + }
> > +}
>
> > +static int upboard_check_supported(struct device *dev, struct regmap *regmap)
> > +{
> > + uint8_t manufacturer_id, build, major, minor, patch;
> > + unsigned int platform_id, firmware_id;
> > + int ret;
>
> > + manufacturer_id = platform_id & 0xff;
>
> Redundant & 0xff part.

Maybe not required, but lets the reader know it's intended.

[...]

> > + ret = upboard_init_gpio(dev);
> > + if (ret) {
> > + if (ret != -EPROBE_DEFER)
> > + dev_err(dev, "failed to init GPIOs: %d", ret);
> > + return ret;
> > + }
>
> I don't know if probe_err() helper is going to be a part of v4.21
> (which this series targets), it would be good to use it.

Interesting. What does it do?

--
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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