linux-kernel - Re: [v6,2/3] reset-controller: ti: introduce a new reset handler

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Date:   Mon, 30 Nov 2020 18:35:05 +0800
From:   Ikjoon Jang <ikjn@...omium.org>
To:     Crystal Guo <crystal.guo@...iatek.com>
Cc:     p.zabel@...gutronix.de, robh+dt@...nel.org, matthias.bgg@...il.com,
        devicetree@...r.kernel.org, yong.liang@...iatek.com,
        stanley.chu@...iatek.com, srv_heupstream@...iatek.com,
        seiya.wang@...iatek.com, linux-kernel@...r.kernel.org,
        fan.chen@...iatek.com, linux-mediatek@...ts.infradead.org,
        yingjoe.chen@...iatek.com, s-anna@...com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [v6,2/3] reset-controller: ti: introduce a new reset handler

On Wed, Sep 30, 2020 at 10:21:58AM +0800, Crystal Guo wrote:
> Introduce ti_syscon_reset() to integrate assert and deassert together.
> If some modules need do serialized assert and deassert operations
> to reset itself, reset_control_reset can be called for convenience.
> 
> Such as reset-qcom-aoss.c, it integrates assert and deassert together
> by 'reset' method. MTK Socs also need this method to perform reset.
> 
> Signed-off-by: Crystal Guo <crystal.guo@...iatek.com>

Reviewed-by: Ikjoon Jang <ikjn@...omium.org>

> ---
>  drivers/reset/reset-ti-syscon.c | 40 ++++++++++++++++++++++++++++++++-
>  1 file changed, 39 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/reset/reset-ti-syscon.c b/drivers/reset/reset-ti-syscon.c
> index a2635c21db7f..5d1f8306cd4f 100644
> --- a/drivers/reset/reset-ti-syscon.c
> +++ b/drivers/reset/reset-ti-syscon.c
> @@ -15,15 +15,22 @@
>   * GNU General Public License for more details.
>   */
>  
> +#include <linux/delay.h>
>  #include <linux/mfd/syscon.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/of_device.h>
>  #include <linux/platform_device.h>
>  #include <linux/regmap.h>
>  #include <linux/reset-controller.h>
>  
>  #include <dt-bindings/reset/ti-syscon.h>
>  
> +struct mediatek_reset_data {
> +	unsigned char *reset_bits;
> +	unsigned int reset_duration_us;
> +};
> +
>  /**
>   * struct ti_syscon_reset_control - reset control structure
>   * @assert_offset: reset assert control register offset from syscon base
> @@ -56,6 +63,7 @@ struct ti_syscon_reset_data {
>  	struct regmap *regmap;
>  	struct ti_syscon_reset_control *controls;
>  	unsigned int nr_controls;
> +	const struct mediatek_reset_data *reset_data;
>  };
>  
>  #define to_ti_syscon_reset_data(rcdev)	\
> @@ -158,9 +166,29 @@ static int ti_syscon_reset_status(struct reset_controller_dev *rcdev,
>  		!(control->flags & STATUS_SET);
>  }
>  
> +static int ti_syscon_reset(struct reset_controller_dev *rcdev,
> +				  unsigned long id)
> +{
> +	struct ti_syscon_reset_data *data = to_ti_syscon_reset_data(rcdev);
> +	int ret;
> +
> +	if (data->reset_data) {
> +		ret = ti_syscon_reset_assert(rcdev, id);
> +		if (ret)
> +			return ret;
> +		usleep_range(data->reset_data->reset_duration_us,
> +			data->reset_data->reset_duration_us * 2);
> +

There are many users using assert() and deassert() seperately
without any delay between them.

If there's a timing requirement between assertion and deassertion,
shouldn't there be a same amount of delay in assert?

> +		return ti_syscon_reset_deassert(rcdev, id);
> +	} else {
> +		return -ENOTSUPP;
> +	}
> +}
> +
>  static const struct reset_control_ops ti_syscon_reset_ops = {
>  	.assert		= ti_syscon_reset_assert,
>  	.deassert	= ti_syscon_reset_deassert,
> +	.reset		= ti_syscon_reset,
>  	.status		= ti_syscon_reset_status,
>  };
>  
> @@ -182,7 +210,11 @@ static int ti_syscon_reset_probe(struct platform_device *pdev)
>  	if (IS_ERR(regmap))
>  		return PTR_ERR(regmap);
>  
> -	list = of_get_property(np, "ti,reset-bits", &size);
> +	data->reset_data = of_device_get_match_data(&pdev->dev);
> +	if (data->reset_data)
> +		list = of_get_property(np, data->reset_data->reset_bits, &size);
> +	else
> +		list = of_get_property(np, "ti,reset-bits", &size);
>  	if (!list || (size / sizeof(*list)) % 7 != 0) {
>  		dev_err(dev, "invalid DT reset description\n");
>  		return -EINVAL;
> @@ -217,8 +249,14 @@ static int ti_syscon_reset_probe(struct platform_device *pdev)
>  	return devm_reset_controller_register(dev, &data->rcdev);
>  }
>  
> +static const struct mediatek_reset_data mtk_reset_data = {
> +	.reset_bits = "mediatek,reset-bits",
> +	.reset_duration_us = 10,
> +};
> +
>  static const struct of_device_id ti_syscon_reset_of_match[] = {
>  	{ .compatible = "ti,syscon-reset", },
> +	{ .compatible = "mediatek,syscon-reset", .data = &mtk_reset_data},
>  	{ /* sentinel */ },
>  };
>  MODULE_DEVICE_TABLE(of, ti_syscon_reset_of_match);