linux-kernel - Re: [PATCH v4 1/9] reset: amlogic: convert driver to regmap

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Message-ID: <1jfrqcrgab.fsf@starbuckisacylon.baylibre.com>
Date: Fri, 06 Sep 2024 16:46:36 +0200
From: Jerome Brunet <jbrunet@...libre.com>
To: Philipp Zabel <p.zabel@...gutronix.de>
Cc: Stephen Boyd <sboyd@...nel.org>,  Neil Armstrong
 <neil.armstrong@...aro.org>,  Kevin Hilman <khilman@...libre.com>,  Martin
 Blumenstingl <martin.blumenstingl@...glemail.com>,  Jiucheng Xu
 <jiucheng.xu@...ogic.com>,  linux-arm-kernel@...ts.infradead.org,
  linux-amlogic@...ts.infradead.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/9] reset: amlogic: convert driver to regmap

On Fri 06 Sep 2024 at 16:19, Philipp Zabel <p.zabel@...gutronix.de> wrote:

> On Fr, 2024-09-06 at 15:34 +0200, Jerome Brunet wrote:
>> To allow using the same driver for the main reset controller and the
>> auxiliary ones embedded in the clock controllers, convert the
>> the Amlogic reset driver to regmap.
>> 
>> Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>
>> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
>> ---
>>  drivers/reset/reset-meson.c | 79 ++++++++++++++++++++++++---------------------
>
> This patch should also make RESET_MESON select REGMAP.

Indeed

>
>>  1 file changed, 43 insertions(+), 36 deletions(-)
>> 
>> diff --git a/drivers/reset/reset-meson.c b/drivers/reset/reset-meson.c
>> index 1e9fca3e30e8..9dd38cc209e2 100644
>> --- a/drivers/reset/reset-meson.c
>> +++ b/drivers/reset/reset-meson.c
>> @@ -11,36 +11,43 @@
>>  #include <linux/of.h>
>>  #include <linux/module.h>
>>  #include <linux/platform_device.h>
>> +#include <linux/regmap.h>
>>  #include <linux/reset-controller.h>
>>  #include <linux/slab.h>
>>  #include <linux/types.h>
>>  
>> -#define BITS_PER_REG	32
>> -
>>  struct meson_reset_param {
>>  	int reg_count;
>>  	int level_offset;
>>  };
>>  
>>  struct meson_reset {
>> -	void __iomem *reg_base;
>>  	const struct meson_reset_param *param;
>>  	struct reset_controller_dev rcdev;
>> -	spinlock_t lock;
>> +	struct regmap *map;
>>  };
>>  
>> +static void meson_reset_offset_and_bit(struct meson_reset *data,
>> +				       unsigned long id,
>> +				       unsigned int *offset,
>> +				       unsigned int *bit)
>> +{
>> +	unsigned int stride = regmap_get_reg_stride(data->map);
>
> You know this is always 4. Having a #define for this (that is also used
> to initialize regmap_config.reg_stride, and for now nr_resets, below)
> instead of going through an exported function would allow the compiler
> to optimize this all away:

Yes, for now. However, with the auxiliary you may get a regmap with
different value. I've seen example with stride = 1. 

I'll admit is very unlikely but I does not really worth it considering
how often we'll get through this and how difficult it will be to debug
if stride ever get different.

>
>> +
>> +	*offset = (id / (stride * BITS_PER_BYTE)) * stride;
>> +	*bit = id % (stride * BITS_PER_BYTE);
>> +}
>> +
>>  static int meson_reset_reset(struct reset_controller_dev *rcdev,
>> -			      unsigned long id)
>> +			     unsigned long id)
>>  {
>>  	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 + (bank << 2);
>> +	unsigned int offset, bit;
>>  
>> -	writel(BIT(offset), reg_addr);
>> +	meson_reset_offset_and_bit(data, id, &offset, &bit);
>>  
>> -	return 0;
>> +	return regmap_write(data->map, offset, BIT(bit));
>>  }
>>  
>>  static int meson_reset_level(struct reset_controller_dev *rcdev,
>> @@ -48,25 +55,13 @@ static int meson_reset_level(struct reset_controller_dev *rcdev,
>>  {
>>  	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;
>> -	unsigned long flags;
>> -	u32 reg;
>> +	unsigned int offset, bit;
>>  
>> -	reg_addr = data->reg_base + data->param->level_offset + (bank << 2);
>> +	meson_reset_offset_and_bit(data, id, &offset, &bit);
>> +	offset += data->param->level_offset;
>>  
>> -	spin_lock_irqsave(&data->lock, flags);
>> -
>> -	reg = readl(reg_addr);
>> -	if (assert)
>> -		writel(reg & ~BIT(offset), reg_addr);
>> -	else
>> -		writel(reg | BIT(offset), reg_addr);
>> -
>> -	spin_unlock_irqrestore(&data->lock, flags);
>> -
>> -	return 0;
>> +	return regmap_update_bits(data->map, offset,
>> +				  BIT(bit), assert ? 0 : BIT(bit));
>
> Matter of taste, perhaps, but the BIT() could be moved into
> meson_reset_offset_and_bit().

It's not really related to this particular patch which is about moving
to regmap.

I can add it to another patch if you want

>
>>  }
>>  
>>  static int meson_reset_assert(struct reset_controller_dev *rcdev,
>> @@ -119,30 +114,42 @@ static const struct of_device_id meson_reset_dt_ids[] = {
>>  };
>>  MODULE_DEVICE_TABLE(of, meson_reset_dt_ids);
>>  
>> +static const struct regmap_config regmap_config = {
>> +	.reg_bits   = 32,
>> +	.val_bits   = 32,
>> +	.reg_stride = 4,
>> +};
>> +
>>  static int meson_reset_probe(struct platform_device *pdev)
>>  {
>> +	struct device *dev = &pdev->dev;
>>  	struct meson_reset *data;
>> +	void __iomem *base;
>>  
>> -	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
>> +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
>>  	if (!data)
>>  		return -ENOMEM;
>>  
>> -	data->reg_base = devm_platform_ioremap_resource(pdev, 0);
>> -	if (IS_ERR(data->reg_base))
>> -		return PTR_ERR(data->reg_base);
>> +	base = devm_platform_ioremap_resource(pdev, 0);
>> +	if (IS_ERR(base))
>> +		return PTR_ERR(base);
>>  
>> -	data->param = of_device_get_match_data(&pdev->dev);
>> +	data->param = of_device_get_match_data(dev);
>>  	if (!data->param)
>>  		return -ENODEV;
>>  
>> -	spin_lock_init(&data->lock);
>> +	data->map = devm_regmap_init_mmio(dev, base, &regmap_config);
>> +	if (IS_ERR(data->map))
>> +		return dev_err_probe(dev, PTR_ERR(data->map),
>> +				     "can't init regmap mmio region\n");
>>  
>>  	data->rcdev.owner = THIS_MODULE;
>> -	data->rcdev.nr_resets = data->param->reg_count * BITS_PER_REG;
>> +	data->rcdev.nr_resets = data->param->reg_count * BITS_PER_BYTE
>> +		* regmap_config.reg_stride;
>>  	data->rcdev.ops = &meson_reset_ops;
>> -	data->rcdev.of_node = pdev->dev.of_node;
>> +	data->rcdev.of_node = dev->of_node;
>>  
>> -	return devm_reset_controller_register(&pdev->dev, &data->rcdev);
>> +	return devm_reset_controller_register(dev, &data->rcdev);
>>  }
>>  
>>  static struct platform_driver meson_reset_driver = {
>
> regards
> Philipp

-- 
Jerome