linux-kernel - Re: [PATCH] rtc: rv3028: add clkout support

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Message-ID: <20191011091738.GC3125@piout.net>
Date:   Fri, 11 Oct 2019 11:17:38 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Parthiban Nallathambi <pn@...x.de>
Cc:     a.zummo@...ertech.it, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org, parthitce@...il.com
Subject: Re: [PATCH] rtc: rv3028: add clkout support

Hi,

thanks for the patch, minor comments below.

On 27/09/2019 16:15:05+0200, Parthiban Nallathambi wrote:
> +	ret = regmap_update_bits(rv3028->regmap, RV3028_STATUS,
> +				 RV3028_STATUS_CLKF, 0);
> +	if (ret < 0)
> +		return ret;
> +

This is already done earlier and this will not be enabled again unless
CLKIE is set which should not happen. So I don't think it is necessary
to do it once again here.

> +	for (i = 0; i < ARRAY_SIZE(clkout_rates); i++) {
> +		if (clkout_rates[i] == rate) {
> +			ret = regmap_update_bits(rv3028->regmap,
> +						 RV3028_CLKOUT,
> +						 RV3028_CLKOUT_FD_MASK, i);
> +			if (ret < 0)
> +				return ret;
> +
> +			return regmap_write(rv3028->regmap, RV3028_CLKOUT,
> +				RV3028_CLKOUT_CLKSY | RV3028_CLKOUT_CLKOE);
> +		}
> +	}
> +
> +	return -EINVAL;
> +}


> +static int rv3028_clkout_register_clk(struct rv3028_data *rv3028,
> +				      struct i2c_client *client)
> +{
> +	int ret;
> +	struct clk *clk;
> +	struct clk_init_data init;
> +	struct device_node *node = client->dev.of_node;
> +
> +	/* disable the clkout output */
> +	ret = regmap_write(rv3028->regmap, RV3028_CLKOUT, 0x0);
> +	if (ret < 0)
> +		return ret;
> +

This is not what the user would expect and could introduce a glitch in 
the clock output every time the platform is booted. If there are no 
users of the clock, then you should probably let the core disable it 
once the boot has ended.


-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com