linux-kernel - Re: [PATCHv6 2/4] iio: adc: exynos_adc: Control special clock of ADC to support Exynos3250 ADC

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Message-ID: <6485839.CnzmD0SeQj@wuerfel>
Date:	Fri, 18 Jul 2014 11:47:42 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Chanwoo Choi <cw00.choi@...sung.com>, jic23@...nel.org,
	ch.naveen@...sung.com, mark.rutland@....com,
	devicetree@...r.kernel.org, kgene.kim@...sung.com,
	pawel.moll@....com, ijc+devicetree@...lion.org.uk,
	linux-iio@...r.kernel.org, t.figa@...sung.com,
	rdunlap@...radead.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
	kyungmin.park@...sung.com, robh+dt@...nel.org, galak@...eaurora.org
Subject: Re: [PATCHv6 2/4] iio: adc: exynos_adc: Control special clock of ADC to support Exynos3250 ADC

On Friday 18 July 2014 14:59:44 Chanwoo Choi wrote:
> This patch control special clock for ADC in Exynos series's FSYS block.
> If special clock of ADC is registerd on clock list of common clk framework,
> Exynos ADC drvier have to control this clock.
> 
> Exynos3250/Exynos4/Exynos5 has 'adc' clock as following:
> - 'adc' clock: bus clock for ADC
> 
> Exynos3250 has additional 'sclk_adc' clock as following:
> - 'sclk_adc' clock: special clock for ADC which provide clock to internal ADC
> 
> Exynos 4210/4212/4412 and Exynos5250/5420 has not included 'sclk_adc' clock
> in FSYS_BLK. But, Exynos3250 based on Cortex-A7 has only included 'sclk_adc'
> clock in FSYS_BLK.

Do you know if any of the older ADC blocks have an "sclk" input as well?

Further, why is it called "sclk_adc" rather than just "sclk"?

> @@ -199,13 +262,20 @@ static void exynos_adc_v2_start_conv(struct exynos_adc *info,
>         writel(con1 | ADC_CON_EN_START, ADC_V2_CON1(info->regs));
>  }
>  
> +#define __EXYNOS_ADC_V2_DATA                           \
> +       .num_channels   = MAX_ADC_V2_CHANNELS,          \
> +       .init_hw        = exynos_adc_v2_init_hw,        \
> +       .exit_hw        = exynos_adc_v2_exit_hw,        \
> +       .clear_irq      = exynos_adc_v2_clear_irq,      \
> +       .start_conv     = exynos_adc_v2_start_conv,     \
> +
>  static struct exynos_adc_data const exynos_adc_v2_data = {
> -       .num_channels   = MAX_ADC_V2_CHANNELS,
> +       __EXYNOS_ADC_V2_DATA
> +};
>  
> -       .init_hw        = exynos_adc_v2_init_hw,
> -       .exit_hw        = exynos_adc_v2_exit_hw,
> -       .clear_irq      = exynos_adc_v2_clear_irq,
> -       .start_conv     = exynos_adc_v2_start_conv,
> +static struct exynos_adc_data const exynos3250_adc_v2_data = {
> +       __EXYNOS_ADC_V2_DATA
> +       .needs_sclk = true,
>  };

I think the macro hurts readability. Please just duplicate the definition
here.

>  static const struct of_device_id exynos_adc_match[] = {
> @@ -215,6 +285,9 @@ static const struct of_device_id exynos_adc_match[] = {
>         }, {
>                 .compatible = "samsung,exynos-adc-v2",
>                 .data = (void *)&exynos_adc_v2_data,
> +       }, {
> +               .compatible = "samsung,exynos3250-adc-v2",
> +               .data = (void *)&exynos3250_adc_v2_data,
>         },
>         {},

Remove the '(void *)' cast here and mark the structure as 'const'.
We intentionally use a 'const void *' type here to verify that
the driver doesn't modify the per-device type data at runtime,
which would be bad if you ever have multiple device instances.

	Arnd
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