linux-kernel - Re: [PATCH] reset: meson: add level reset support for GX SoC family

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Message-ID: <489c147c-9972-68ef-3475-322f56d4a620@baylibre.com>
Date:   Tue, 17 Oct 2017 12:09:54 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] reset: meson: add level reset support for GX SoC family

On 17/10/2017 12:08, Philipp Zabel wrote:
> Hi Neil,
> 
> On Mon, 2017-10-16 at 17:26 +0200, Neil Armstrong wrote:
>> The Amlogic GX SoC family embeds alternate registers to drive the reset
>> levels next to the pulse registers.
>>
>> This patch adds support for level reset handling on the GX family only.
>>
>> The Meson8 family has an alternate way to handle level reset.
>>
>> Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> 
> thank you for the patch, comments below:
> 
>> ---
>>  drivers/reset/reset-meson.c | 57 +++++++++++++++++++++++++++++++++++++++++----
>>  1 file changed, 53 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/reset/reset-meson.c b/drivers/reset/reset-meson.c
>> index a8b915e..d55e440 100644
>> --- a/drivers/reset/reset-meson.c
>> +++ b/drivers/reset/reset-meson.c
>> @@ -62,9 +62,11 @@
>>  #include <linux/reset-controller.h>
>>  #include <linux/slab.h>
>>  #include <linux/types.h>
>> +#include <linux/of_device.h>
>>  
>>  #define REG_COUNT	8
>>  #define BITS_PER_REG	32
>> +#define LEVEL_OFFSET	0x7c
>>  
>>  struct meson_reset {
>>  	void __iomem *reg_base;
>> @@ -88,18 +90,61 @@ static int meson_reset_reset(struct reset_controller_dev *rcdev,
>>  	return 0;
>>  }
>>  
>> -static const struct reset_control_ops meson_reset_ops = {
>> +static int meson_reset_level(struct reset_controller_dev *rcdev,
>> +			    unsigned long id, bool assert)
>> +{
>> +	struct meson_reset *data =
>> +		container_of(rcdev, struct meson_reset, rcdev);
>> +	unsigned int bank = id / BITS_PER_REG;
>> +	unsigned int offset = id % BITS_PER_REG;
>> +	void __iomem *reg_addr = data->reg_base + LEVEL_OFFSET + (bank << 2);
>> +	u32 reg;
>> +
>> +	if (bank >= REG_COUNT)
>> +		return -EINVAL;
> 
> This check is not necessary. The same check is in meson_reset_reset,
> which I didn't notice last time.
> 
> of_reset_simple_xlate, the default rcdev->of_xlate implementation,
> already guarantees id < rcdev->nr_resets. And since nr_resets is set to
> REG_COUNT * BITS_PER_REG, we know that id < REG_COUNT * BITS_PER_REG and
> thus bank <= id / BITS_PER_REG < REG_COUNT.

Ok will remove.

> 
>> +	reg = readl(reg_addr);
>> +	if (assert)
>> +		writel(reg & ~BIT(offset), reg_addr);
>> +	else
>> +		writel(reg | BIT(offset), reg_addr);
> 
> These read-modify-write operations must be protected by a spinlock.

Ok will add

> 
>> +
>> +	return 0;
>> +}
>> +
>> +static int meson_reset_assert(struct reset_controller_dev *rcdev,
>> +			      unsigned long id)
>> +{
>> +	return meson_reset_level(rcdev, id, true);
>> +}
>> +
>> +static int meson_reset_deassert(struct reset_controller_dev *rcdev,
>> +				unsigned long id)
>> +{
>> +	return meson_reset_level(rcdev, id, false);
>> +}
>> +
>> +static const struct reset_control_ops meson_reset_meson8_ops = {
>> +	.reset		= meson_reset_reset,
>> +};
>> +
>> +static const struct reset_control_ops meson_reset_gx_ops = {
>>  	.reset		= meson_reset_reset,
>> +	.assert		= meson_reset_assert,
>> +	.deassert	= meson_reset_deassert,
>>  };
>>  
>>  static const struct of_device_id meson_reset_dt_ids[] = {
>> -	 { .compatible = "amlogic,meson8b-reset", },
>> -	 { .compatible = "amlogic,meson-gxbb-reset", },
>> +	 { .compatible = "amlogic,meson8b-reset",
>> +	   .data = (void *) &meson_reset_meson8_ops, },
>> +	 { .compatible = "amlogic,meson-gxbb-reset",
>> +	   .data = (void *) &meson_reset_gx_ops, },
>>  	 { /* sentinel */ },
>>  };
> 
> of_device_id.data ist const void *, so there is no need to cast here.

Ok will remove then

> 
>>  static int meson_reset_probe(struct platform_device *pdev)
>>  {
>> +	const struct reset_control_ops *ops;
>>  	struct meson_reset *data;
>>  	struct resource *res;
>>  
>> @@ -107,6 +152,10 @@ static int meson_reset_probe(struct platform_device *pdev)
>>  	if (!data)
>>  		return -ENOMEM;
>>  
>> +	ops = of_device_get_match_data(&pdev->dev);
>> +	if (!ops)
>> +		return -EINVAL;
>> +
>>  	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>>  	data->reg_base = devm_ioremap_resource(&pdev->dev, res);
>>  	if (IS_ERR(data->reg_base))
>> @@ -116,7 +165,7 @@ static int meson_reset_probe(struct platform_device *pdev)
>>  
>>  	data->rcdev.owner = THIS_MODULE;
>>  	data->rcdev.nr_resets = REG_COUNT * BITS_PER_REG;
>> -	data->rcdev.ops = &meson_reset_ops;
>> +	data->rcdev.ops = ops;
>>  	data->rcdev.of_node = pdev->dev.of_node;
>>  
>>  	return devm_reset_controller_register(&pdev->dev, &data->rcdev);
> 
> regards
> Philipp
> 

Thanks,
Neil