Re: [RESEND PATCH v5 3/5] IIO: Ingenic JZ47xx: Add touchscreen mode.

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Hi Andy,
thanks for the review. Comments inline.

On 2020-04-17 22:59, Andy Shevchenko wrote:
On Fri, Apr 17, 2020 at 11:21 PM Artur Rojek <contact@xxxxxxxxxxxxxx> wrote:

The SADC component in JZ47xx SoCs provides support for touchscreen
operations (pen position and pen down pressure) in single-ended and
differential modes.

Of the known hardware to use this controller, GCW Zero and Anbernic RG-350 utilize the touchscreen mode by having their joystick(s) attached to the
X/Y positive/negative input pins.
GCW Zero comes with a single joystick and is sufficiently handled with the
currently implemented single-ended mode. Support for boards with two
joysticks, where one is hooked up to Xn/Yn and the other to Xp/Yp channels
will need to be provided in the future.

The touchscreen component of SADC takes a significant time to stabilize after first receiving the clock and a delay of 50ms has been empirically
proven to be a safe value before data sampling can begin.

All the boards which probe this driver have the interrupt provided from devicetree, with no need to handle a case where the irq was not provided.

Device Tree
IRQ

...

+               .scan_type = {
+                       .sign = 'u',
+                       .realbits = 12,

+                       .storagebits = 16

It's slightly better to leave comma in such cases.

+               },

+               .scan_type = {
+                       .sign = 'u',
+                       .realbits = 12,

+                       .storagebits = 16

Ditto.

+               },

...

                .indexed = 1,
                .channel = INGENIC_ADC_AUX,
+               .scan_index = -1

Ditto. You see above? Isn't it nice that you didn't touch that line?
So, perhaps next developer can leverage this subtle kind of things.

                .indexed = 1,
                .channel = INGENIC_ADC_BATTERY,
+               .scan_index = -1

Ditto.

                .indexed = 1,
                .channel = INGENIC_ADC_AUX2,
+               .scan_index = -1

Ditto.

...

+static int ingenic_adc_buffer_enable(struct iio_dev *iio_dev)
+{
+       struct ingenic_adc *adc = iio_priv(iio_dev);
+

+       clk_enable(adc->clk);

Error check?

+ /* It takes significant time for the touchscreen hw to stabilize. */
+       msleep(50);
+       ingenic_adc_set_config(adc, JZ_ADC_REG_CFG_TOUCH_OPS_MASK,
+                              JZ_ADC_REG_CFG_SAMPLE_NUM(4) |
+                              JZ_ADC_REG_CFG_PULL_UP(4));
+       writew(80, adc->base + JZ_ADC_REG_ADWAIT);
+       writew(2, adc->base + JZ_ADC_REG_ADSAME);

+       writeb((u8)~JZ_ADC_IRQ_TOUCH, adc->base + JZ_ADC_REG_CTRL);

Why casting?
After flipping the bits, the resulting value can't be represented by u8. Since we care only about the first 8 bits anyway, explicit cast here is to silence a compiler warning.

+       writel(0, adc->base + JZ_ADC_REG_ADTCH);
+       ingenic_adc_enable(adc, 2, true);
+
+       return 0;
+}

+       irq = platform_get_irq(pdev, 0);

Before it worked w/o IRQ, here is a regression you introduced.

+       if (irq < 0) {

+               dev_err(dev, "Failed to get irq: %d\n", irq);

Redundant message.

+               return irq;
+       }

- Artur



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