linux-kernel - Re: [PATCH RESEND 0/6 v10] gpio: Add block GPIO

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Message-ID: <50D01402.9090301@grandegger.com>
Date:	Tue, 18 Dec 2012 07:58:10 +0100
From:	Wolfgang Grandegger <wg@...ndegger.com>
To:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
CC:	Roland Stigge <stigge@...com.de>, rmallon@...il.com,
	gregkh@...uxfoundation.org, linus.walleij@...aro.org,
	broonie@...nsource.wolfsonmicro.com, w.sang@...gutronix.de,
	linux-kernel@...r.kernel.org, grant.likely@...retlab.ca,
	daniel-gl@....net, sr@...x.de,
	linux-arm-kernel@...ts.infradead.org, highguy@...il.com
Subject: Re: [PATCH RESEND 0/6 v10] gpio: Add block GPIO

On 12/18/2012 06:55 AM, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 20:47 Mon 17 Dec     , Wolfgang Grandegger wrote:
>> On 12/17/2012 07:02 PM, Roland Stigge wrote:
>>> On 12/17/2012 06:37 PM, Wolfgang Grandegger wrote:
>>>> 	/* Do synchronous data output with a single write access */
>>>> 	__raw_writel(~mask, pio + PIO_OWDR);
>>>> 	__raw_writel(mask, pio + PIO_OWER);
>>>> 	__raw_writel(val, pio + PIO_ODSR);
>>>>
>>>> For caching we would need a storage. Not sure if it's worth compared to
>>>> a context switch into the kernel.
>>>
>>> Block GPIO is not only for you in userspace. ;-) You can also implement
>>> efficient n-bit bus I/O in kernel drivers, n-bit-banging. :-) So not
>>> always context switches involved.
>>
>> OK, what do you think about the following untested patch:
>>
>> From b44cad16cbbca84715dffd4cb5268497216add25 Mon Sep 17 00:00:00 2001
>> From: Wolfgang Grandegger <wg@...ndegger.com>
>> Date: Mon, 3 Dec 2012 08:31:55 +0100
>> Subject: [PATCH 1/2] gpio: add GPIO block callback functions for AT91
>>
>> Signed-off-by: Wolfgang Grandegger <wg@...ndegger.com>
>> ---
>>  arch/arm/mach-at91/gpio.c |   29 +++++++++++++++++++++++++++++
>>  1 file changed, 29 insertions(+)
>>
>> diff --git a/arch/arm/mach-at91/gpio.c b/arch/arm/mach-at91/gpio.c
>> index be42cf0..cf6bd45 100644
>> --- a/arch/arm/mach-at91/gpio.c
>> +++ b/arch/arm/mach-at91/gpio.c
>> @@ -42,13 +42,16 @@ struct at91_gpio_chip {
>>  	void __iomem		*regbase;	/* PIO bank virtual address */
>>  	struct clk		*clock;		/* associated clock */
>>  	struct irq_domain	*domain;	/* associated irq domain */
>> +	unsigned long		mask_shadow;	/* synchronous data output */
>>  };
>>  
>>  #define to_at91_gpio_chip(c) container_of(c, struct at91_gpio_chip, chip)
>>  
>>  static void at91_gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip);
>>  static void at91_gpiolib_set(struct gpio_chip *chip, unsigned offset, int val);
>> +static void at91_gpiolib_set_block(struct gpio_chip *chip, unsigned long mask, unsigned long val);
>>  static int at91_gpiolib_get(struct gpio_chip *chip, unsigned offset);
>> +static unsigned long at91_gpiolib_get_block(struct gpio_chip *chip, unsigned long mask);
>>  static int at91_gpiolib_direction_output(struct gpio_chip *chip,
>>  					 unsigned offset, int val);
>>  static int at91_gpiolib_direction_input(struct gpio_chip *chip,
>> @@ -62,7 +65,9 @@ static int at91_gpiolib_to_irq(struct gpio_chip *chip, unsigned offset);
>>  			.direction_input  = at91_gpiolib_direction_input, \
>>  			.direction_output = at91_gpiolib_direction_output, \
>>  			.get		  = at91_gpiolib_get,		\
>> +			.get_block	  = at91_gpiolib_get_block,	\
>>  			.set		  = at91_gpiolib_set,		\
>> +			.set_block	  = at91_gpiolib_set_block,	\
>>  			.dbg_show	  = at91_gpiolib_dbg_show,	\
>>  			.to_irq		  = at91_gpiolib_to_irq,	\
>>  			.ngpio		  = nr_gpio,			\
>> @@ -896,6 +901,16 @@ static int at91_gpiolib_get(struct gpio_chip *chip, unsigned offset)
>>  	return (pdsr & mask) != 0;
>>  }
>>  
>> +static unsigned long at91_gpiolib_get_block(struct gpio_chip *chip, unsigned long mask)
>> +{
>> +	struct at91_gpio_chip *at91_gpio = to_at91_gpio_chip(chip);
>> +	void __iomem *pio = at91_gpio->regbase;
>> +	u32 pdsr;
>> +
>> +	pdsr = __raw_readl(pio + PIO_PDSR);
>> +	return pdsr & mask;
>> +}
>> +
>>  static void at91_gpiolib_set(struct gpio_chip *chip, unsigned offset, int val)
>>  {
>>  	struct at91_gpio_chip *at91_gpio = to_at91_gpio_chip(chip);
>> @@ -905,6 +920,20 @@ static void at91_gpiolib_set(struct gpio_chip *chip, unsigned offset, int val)
>>  	__raw_writel(mask, pio + (val ? PIO_SODR : PIO_CODR));
>>  }
>>  
>> +static void at91_gpiolib_set_block(struct gpio_chip *chip, unsigned long mask, unsigned long val)
>> +{
>> +	struct at91_gpio_chip *at91_gpio = to_at91_gpio_chip(chip);
>> +	void __iomem *pio = at91_gpio->regbase;
>> +
>> +	/* Do synchronous data output with a single write access */
>> +	if (mask != at91_gpio->mask_shadow) {
>> +		at91_gpio->mask_shadow = mask;
>> +		__raw_writel(~mask, pio + PIO_OWDR);
>> +		__raw_writel(mask, pio + PIO_OWER);
>> +	}
>> +	__raw_writel(val, pio + PIO_ODSR);
>> +}
> this driver is only for old at91 platfrom if you touch at91 you need to update
> the pinctrl too

Well, the patch is for the hardware I have at hand and I can test. There
are many other GPIO hardware interfaces which could be enhanced with
block gpio. Roland only did it for the interfaces in driver/gpio. Also,
I think, an ACK for this patch series would be nice before we continue.

Wolfgang.

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