Re: [PATCH v2 2/3] iio: adc: Enable multiple consecutive channels based on model data

Andy Shevchenko
2026-03-16T14:25:42Z

On Mon, Mar 16, 2026 at 11:00:47AM +0800, Billy Tsai wrote:
> Add helpers to generate channel masks and enable multiple ADC channels
> according to the device model's channel count.

...

> +

(1)

> +/*
> + * Enable multiple consecutive channels starting from channel 0.
> + * This creates a bitmask for channels 0 to (num_channels - 1).
> + * For example: num_channels=3 creates mask 0x0007 (channels 0,1,2)
> + */
> +static inline u32 aspeed_adc_channels_mask(unsigned int num_channels)
> +{
> + if (num_channels == 0)
> + return 0;

> + if (num_channels >= 16)
> + return GENMASK(15, 0);
> + return GENMASK(num_channels - 1, 0);

This entire function can be folded into

return BIT(min(num_channels, 16U)) - 1;

Or

if (num_channels > 16)
return GENMASK(15, 0);

return BIT(num_channels) - 1;

> +}

> +/*
> + * Helper function to enable multiple channels in the control register
> + */
> +static inline u32 aspeed_adc_enable_channels(unsigned int num_channels)
> +{
> + return FIELD_PREP(ASPEED_ADC_CTRL_CHANNEL, aspeed_adc_channels_mask(num_channels));
> +}

> +

One of these (see 1 above) new blank lines should be rather added in the previous patch.

> /* Battery sensing is typically on the last channel */
> #define ASPEED_ADC_BATTERY_CHANNEL 7

...

> /* Start all channels in normal mode. */
> - adc_engine_control_reg_val =
> - readl(data->base + ASPEED_REG_ENGINE_CONTROL);
> - adc_engine_control_reg_val |= ASPEED_ADC_CTRL_CHANNEL;
> + adc_engine_control_reg_val = readl(data->base + ASPEED_REG_ENGINE_CONTROL);

> + adc_engine_control_reg_val |=
> + aspeed_adc_enable_channels(aspeed_adc_get_active_channels(data));

Why not FIELD_MODIFY()?

> writel(adc_engine_control_reg_val,
> data->base + ASPEED_REG_ENGINE_CONTROL);

--
With Best Regards,
Andy Shevchenko