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SubjectRe: [PATCH v2 1/3] mfd: upboard: Add UP2 platform controller driver
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On 10/20/2018 12:49 PM, 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?
Sure: https://gist.github.com/Dan-Emutex/6382c25f4b8b8cdd80e6056889cdf48b
I'll add this to the cover letter for v3 as well.

>
>> +#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)
These were added in response to one of your review comments on the original patch-set ;)
I think they do slightly improve the code readability so I'll leave them there if there are no objections.

>
>
>> +static void __reg_io_write(const struct upboard_ddata * const ddata,
>> + unsigned int size, unsigned int val)
>> +{
>> + int i;
>> +
>> + /*
>> + * DATAIN is latched on each rising edge of the STROBE signal.
>> + * Data (register address or value) is sent MSb first.
>> + */
>> + for (i = size - 1; i >= 0; i--) {
> while (size--)
Yep, much neater.  I'll change that, thanks!  Ditto for the other comments on this file.+ 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.
I left this out for now in case it causes any awkwardness with merging.  Hope that's ok.

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