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

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Message-ID: <50CF76D3.9030708@grandegger.com>
Date:	Mon, 17 Dec 2012 20:47:31 +0100
From:	Wolfgang Grandegger <wg@...ndegger.com>
To:	Roland Stigge <stigge@...com.de>
CC:	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,
	plagnioj@...osoft.com, linux-arm-kernel@...ts.infradead.org,
	highguy@...il.com
Subject: Re: [PATCH RESEND 0/6 v10] gpio: Add block GPIO

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);
+}
+
 static void at91_gpiolib_dbg_show(struct seq_file *s, struct gpio_chip *chip)
 {
 	int i;
-- 
1.7.9.5


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