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Date: Mon, 29 Dec 2008 11:38:07 +0800
From: "Eric Miao" <eric.y.miao@...il.com>
To: "Jaya Kumar" <jayakumar.lkml@...il.com>
Cc: "David Brownell" <dbrownell@...rs.sourceforge.net>,
"Eric Miao" <eric.miao@...vell.com>,
"Paulius Zaleckas" <paulius.zaleckas@...tonika.lt>,
"Geert Uytterhoeven" <geert@...ux-m68k.org>,
"David Brownell" <david-b@...bell.net>,
"Sam Ravnborg" <sam@...nborg.org>,
"Haavard Skinnemoen" <hskinnemoen@...el.com>,
"Philipp Zabel" <philipp.zabel@...il.com>,
"Russell King" <rmk@....linux.org.uk>,
"Ben Gardner" <bgardner@...tec.com>, "Greg KH" <greg@...ah.com>,
linux-arm-kernel@...ts.arm.linux.org.uk,
linux-fbdev-devel@...ts.sourceforge.net,
linux-kernel@...r.kernel.org
Subject: Re: [RFC 2.6.27 1/1] gpiolib: add batch set/get
On Sun, Dec 28, 2008 at 12:24 AM, Jaya Kumar <jayakumar.lkml@...il.com> wrote:
> Hi friends,
>
> This is v2 of my attempt to add batch support to gpiolib. Thanks to
> David Brownell, Eric Miao, Paulius Zaleckas, Geert, and Sam for prior
> feedback. I have tested set_batch using the am300 driver. get_batch
> is not tested.
>
> Please let me know your feedback.
>
> Thanks,
> jaya
>
> am300epd was doing 800*600*16*gpio_set_value for each framebuffer transfer
> (it uses 16-pins of gpio as its data bus). I found this caused a wee
> performance limitation. This patch adds an API for gpio_s/get_batch
> which allows drivers to s/get batches of gpio together in a single call.
> I have done a test implementation on gumstix (pxa255) with am300epd
> and it provides a nice improvement in performance.
>
> Signed-off-by: Jaya Kumar <jayakumar.lkml@...il.com>
> Cc: David Brownell <dbrownell@...rs.sourceforge.net>
> Cc: Eric Miao <eric.miao@...vell.com>
> Cc: Paulius Zaleckas <paulius.zaleckas@...tonika.lt>
> Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
> Cc: David Brownell <david-b@...bell.net>
> Cc: Sam Ravnborg <sam@...nborg.org>
> Cc: Haavard Skinnemoen <hskinnemoen@...el.com>
> Cc: Philipp Zabel <philipp.zabel@...il.com>
> Cc: Russell King <rmk@....linux.org.uk>
> Cc: Ben Gardner <bgardner@...tec.com>
> CC: Greg KH <greg@...ah.com>
> Cc: linux-arm-kernel@...ts.arm.linux.org.uk
> Cc: linux-fbdev-devel@...ts.sourceforge.net
> Cc: linux-kernel@...r.kernel.org
> ---
> arch/arm/mach-pxa/Kconfig | 1 +
> arch/arm/mach-pxa/am300epd.c | 9 ++-
> arch/arm/mach-pxa/gpio.c | 72 +++++++++++++++++++
> arch/arm/mach-pxa/include/mach/gpio.h | 47 +++++++++++++
> drivers/gpio/Kconfig | 5 ++
> drivers/gpio/gpiolib.c | 122 +++++++++++++++++++++++++++++++++
> include/asm-generic/gpio.h | 15 ++++-
> 7 files changed, 269 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/mach-pxa/Kconfig b/arch/arm/mach-pxa/Kconfig
> index 768618b..a5a306e 100644
> --- a/arch/arm/mach-pxa/Kconfig
> +++ b/arch/arm/mach-pxa/Kconfig
> @@ -41,6 +41,7 @@ config GUMSTIX_AM200EPD
> bool "Enable AM200EPD board support"
>
> config GUMSTIX_AM300EPD
> + select GPIOLIB_BATCH
> bool "Enable AM300EPD board support"
>
> endchoice
> diff --git a/arch/arm/mach-pxa/am300epd.c b/arch/arm/mach-pxa/am300epd.c
> index 4bd10a1..9594cf0 100644
> --- a/arch/arm/mach-pxa/am300epd.c
> +++ b/arch/arm/mach-pxa/am300epd.c
> @@ -190,9 +190,12 @@ static u16 am300_get_hdb(struct broadsheetfb_par *par)
> u16 res = 0;
> int i;
>
> +#ifdef CONFIG_GPIOLIB_BATCH
> + res = gpio_get_batch(DB0_GPIO_PIN, 0xFFFF, 16);
> +#else
> for (i = 0; i <= (DB15_GPIO_PIN - DB0_GPIO_PIN) ; i++)
> res |= (gpio_get_value(DB0_GPIO_PIN + i)) ? (1 << i) : 0;
> -
> +#endif
> return res;
> }
>
> @@ -200,8 +203,12 @@ static void am300_set_hdb(struct broadsheetfb_par *par, u16 data)
> {
> int i;
>
> +#ifdef CONFIG_GPIOLIB_BATCH
> + gpio_set_batch(DB0_GPIO_PIN, data, 0xFFFF, 16);
> +#else
> for (i = 0; i <= (DB15_GPIO_PIN - DB0_GPIO_PIN) ; i++)
> gpio_set_value(DB0_GPIO_PIN + i, (data >> i) & 0x01);
> +#endif
Well, if AM300 selects GPIOLIB_BATCH, I don't think we need the
gpio_set_value() stuffs, and get rid of this #ifdef completely.
> }
>
>
> diff --git a/arch/arm/mach-pxa/gpio.c b/arch/arm/mach-pxa/gpio.c
> index 5fec1e4..d85cf2e 100644
> --- a/arch/arm/mach-pxa/gpio.c
> +++ b/arch/arm/mach-pxa/gpio.c
> @@ -162,6 +162,76 @@ static void pxa_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
> __raw_writel(mask, pxa->regbase + GPCR_OFFSET);
> }
>
> +#ifdef CONFIG_GPIOLIB_BATCH
> +/*
> + * Set output GPIO level in batches
> + */
> +static void pxa_gpio_set_batch(struct gpio_chip *chip, unsigned offset,
> + u32 values, u32 bitmask)
> +{
> + struct pxa_gpio_chip *pxa;
> +
> + /* we're guaranteed by the caller that offset + bitmask remains
> + * in this chip.
> + */
> + pxa = container_of(chip, struct pxa_gpio_chip, chip);
> +
> + /* shift the bits into our register specific position */
> + values <<= offset;
> + bitmask <<= offset;
> +
> + values &= bitmask;
or a single 'values = (values & bitmask) << offset' ?
> + if (values)
> + __raw_writel(values, pxa->regbase + GPSR_OFFSET);
> +
> + values = ~values;
> + values &= bitmask;
ditto
> + if (values)
> + __raw_writel(values, pxa->regbase + GPCR_OFFSET);
> +}
> +
> +/*
> + * Get output GPIO level in batches
> + */
> +static u32 pxa_gpio_get_batch(struct gpio_chip *chip, unsigned offset,
> + u32 bitmask)
> +{
> + u32 values;
> + struct pxa_gpio_chip *pxa;
> +
> + /* we're guaranteed by the caller that offset + bitmask remains
> + * in this chip.
> + */
> + pxa = container_of(chip, struct pxa_gpio_chip, chip);
> +
> + values = __raw_readl(pxa->regbase + GPLR_OFFSET);
> +
> + /* shift the result back into original position */
> + values >>= offset;
> + /* no need to shift bitmask since we've already shifted values */
> + values &= bitmask;
> +
> + return values;
or a single 'return (values >> offset) & bitmask;' should be enough.
> +}
> +#endif
> +
> +#ifdef CONFIG_GPIOLIB_BATCH
> +#define GPIO_CHIP(_n) \
> + [_n] = { \
> + .regbase = GPIO##_n##_BASE, \
> + .chip = { \
> + .label = "gpio-" #_n, \
> + .direction_input = pxa_gpio_direction_input, \
> + .direction_output = pxa_gpio_direction_output, \
> + .get = pxa_gpio_get, \
> + .set = pxa_gpio_set, \
> + .base = (_n) * 32, \
> + .ngpio = 32, \
> + .set_batch = pxa_gpio_set_batch, \
> + .get_batch = pxa_gpio_get_batch, \
This is a bit ugly, define pxa_gpio_set_batch to NULL #ifndef GPIOLIB_BATCH
in the above code, and force .{set,get}_batch assignment anyway, this will
look a bit better, the same way as PM. However, this requires a modification
to gpio_chip to always allow these two pointers, which might be a concern.
> + }, \
> + }
> +#else
> #define GPIO_CHIP(_n) \
> [_n] = { \
> .regbase = GPIO##_n##_BASE, \
> @@ -175,6 +245,8 @@ static void pxa_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
> .ngpio = 32, \
> }, \
> }
> +#endif
> +
>
> static struct pxa_gpio_chip pxa_gpio_chip[] = {
> GPIO_CHIP(0),
> diff --git a/arch/arm/mach-pxa/include/mach/gpio.h b/arch/arm/mach-pxa/include/mach/gpio.h
> index 2c538d8..e66e752 100644
> --- a/arch/arm/mach-pxa/include/mach/gpio.h
> +++ b/arch/arm/mach-pxa/include/mach/gpio.h
> @@ -56,6 +56,53 @@ static inline void gpio_set_value(unsigned gpio, int value)
> }
> }
>
> +#ifdef CONFIG_GPIOLIB_BATCH
> +static inline void gpio_set_batch(unsigned gpio, u32 values, u32 bitmask,
> + int bitwidth)
> +{
> + if (__builtin_constant_p(gpio) &&
> + (gpio + bitwidth < NR_BUILTIN_GPIO) &&
> + ((gpio + bitwidth) <= roundup(gpio+1, 32))) {
> + int shift;
> +
> + shift = gpio % 32;
> + values <<= shift;
> + bitmask <<= shift;
> +
> + values &= bitmask;
> + if (values)
> + GPSR(gpio) = values;
> +
> + values = ~values;
> + values &= bitmask;
> + if (values)
> + GPCR(gpio) = values;
I doubt the optimization of GPIO being a constant is essential for
batch operation ... anyway, this is plus.
> + } else {
> + __gpio_set_batch(gpio, values, bitmask, bitwidth);
> + }
> +}
> +
> +static inline u32 gpio_get_batch(unsigned gpio, u32 bitmask, int bitwidth)
> +{
> + if (__builtin_constant_p(gpio) &&
> + (gpio + bitwidth < NR_BUILTIN_GPIO) &&
> + ((gpio + bitwidth) <= roundup(gpio+1, 32))) {
> + int shift;
> + u32 values;
> +
> + shift = gpio % 32;
> +
> + values = GPLR(gpio);
> + values >>= shift;
> + values &= bitmask;
> +
> + return values;
> + } else {
> + return __gpio_get_batch(gpio, bitmask, bitwidth);
> + }
> +}
> +#endif
> +
> #define gpio_cansleep __gpio_cansleep
>
> #define gpio_to_irq(gpio) IRQ_GPIO(gpio)
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index 48f49d9..aeeb83c 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -37,6 +37,11 @@ menuconfig GPIOLIB
>
> if GPIOLIB
>
> +config GPIOLIB_BATCH
> + bool "Batch GPIO support"
> + help
> + Say Y here to add the capability to batch set/get GPIOs.
> +
> config DEBUG_GPIO
> bool "Debug GPIO calls"
> depends on DEBUG_KERNEL
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 82020ab..7b36573 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1056,6 +1056,128 @@ void __gpio_set_value(unsigned gpio, int value)
> }
> EXPORT_SYMBOL_GPL(__gpio_set_value);
>
> +#ifdef CONFIG_GPIOLIB_BATCH
> +/**
> + * __gpio_set_batch() - assign a batch of gpio pins together
> + * @gpio: starting gpio pin
> + * @values: values to assign, sequential and including masked bits
> + * @bitmask: bitmask to be applied to values
> + * @bitwidth: width inclusive of masked-off bits
> + * Context: any
> + *
> + * This is used directly or indirectly to implement gpio_set_value().
> + * It invokes the associated gpio_chip.set_batch() method. If that
> + * method does not exist for any segment that is involved, then it drops
> + * back down to standard gpio_chip.set()
> + */
> +void __gpio_set_batch(unsigned gpio, u32 values, u32 bitmask, int bitwidth)
> +{
> + struct gpio_chip *chip;
> + int i = 0;
> + int value, width, remwidth;
> + u32 mask;
> +
> + do {
> + chip = gpio_to_chip(gpio + i);
> + WARN_ON(extra_checks && chip->can_sleep);
> +
> + if (!chip->set_batch) {
> + while (((gpio + i) < (chip->base + chip->ngpio))
> + && bitwidth) {
> + mask = 1 << i;
> + value = values & mask;
> + if (bitmask & mask)
> + chip->set(chip, gpio + i - chip->base,
> + value);
> + i++;
> + bitwidth--;
I recommend this being put into something like 'default_gpio_set_batch', and
assign this to 'chip->set_batch' when the gpio chip is being registered and
found 'chip->set_batch == NULL', so to keep this block consistent.
Same comment to the 'get_batch' implementation below.
> + }
> + } else {
> + value = values >> i; /* shift off the used data bits */
> + remwidth = ((chip->base + (int) chip->ngpio) -
> + ((int) gpio + i));
> + width = min(bitwidth, remwidth);
> +
> + /* shift off the used mask bits */
> + mask = bitmask >> i;
> + /* now adjust mask by width of set */
> + mask &= ((1 << width) - 1);
> +
> + chip->set_batch(chip, gpio + i - chip->base, value,
> + mask);
> + i += width;
> + bitwidth -= width;
> + }
> + } while (bitwidth);
> +}
> +EXPORT_SYMBOL_GPL(__gpio_set_batch);
> +
> +/**
> + * __gpio_get_batch() - get a batch of gpio pins together
> + * @gpio: starting gpio pin
> + * @bitmask: bitmask to be applied to values
> + * @bitwidth: width inclusive of masked-off bits
> + * Context: any
> + *
> + * This is used directly or indirectly to implement gpio_get_value().
> + * It invokes the associated gpio_chip.get_batch() method and returns
> + * zero if no such method is provided.
> + */
> +u32 __gpio_get_batch(unsigned gpio, u32 bitmask, int bitwidth)
> +{
> + struct gpio_chip *chip;
> + int i = 0;
> + int width, remwidth;
> + u32 mask;
> + u32 values = 0;
> + u32 value;
> +
> + do {
> + chip = gpio_to_chip(gpio + i);
> + WARN_ON(extra_checks && chip->can_sleep);
> +
> + /*
> + * check if we have batch capability on this chip.
> + * if not, then we use the single bit gets
> + * any masked or inaccessible bits are already 0
> + */
> + if (!chip->get_batch) {
> + while (((gpio + i) < (chip->base + chip->ngpio))
> + && bitwidth) {
> + mask = 1 << i;
> + /* skip if no get or masked out */
> + if (chip->get && (bitmask & mask)) {
> + if (chip->get(chip,
> + gpio + i - chip->base))
> + values |= mask;
> + }
> + i++;
> + bitwidth--;
> + }
> + } else {
> + remwidth = ((chip->base + (int) chip->ngpio) -
> + ((int) gpio + i));
> + width = min(bitwidth, remwidth);
> +
> + /* shift off the used mask bits */
> + mask = bitmask >> i;
> + /* now adjust mask by width of get */
> + mask &= ((1 << width) - 1);
> +
> + value = chip->get_batch(chip, gpio + i - chip->base,
> + mask);
> + /* shift result back into caller position */
> + values |= value << i;
> + i += width;
> + bitwidth -= width;
> + }
> + } while (bitwidth);
> +
> + return values;
> +}
> +EXPORT_SYMBOL_GPL(__gpio_get_batch);
> +#endif
> +
> /**
> * __gpio_cansleep() - report whether gpio value access will sleep
> * @gpio: gpio in question
> diff --git a/include/asm-generic/gpio.h b/include/asm-generic/gpio.h
> index 81797ec..fa716a7 100644
> --- a/include/asm-generic/gpio.h
> +++ b/include/asm-generic/gpio.h
> @@ -44,6 +44,8 @@ struct module;
> * returns either the value actually sensed, or zero
> * @direction_output: configures signal "offset" as output, or returns error
> * @set: assigns output value for signal "offset"
> + * @set_batch: batch assigns output values for consecutive signals starting at
> + * "offset" with mask in "bitmask" all within this gpio_chip
> * @to_irq: optional hook supporting non-static gpio_to_irq() mappings;
> * implementation may not sleep
> * @dbg_show: optional routine to show contents in debugfs; default code
> @@ -84,7 +86,13 @@ struct gpio_chip {
> unsigned offset, int value);
> void (*set)(struct gpio_chip *chip,
> unsigned offset, int value);
> -
> +#ifdef CONFIG_GPIOLIB_BATCH
> + void (*set_batch)(struct gpio_chip *chip,
> + unsigned offset, u32 values,
> + u32 bitmask);
> + u32 (*get_batch)(struct gpio_chip *chip,
> + unsigned offset, u32 bitmask);
> +#endif
> int (*to_irq)(struct gpio_chip *chip,
> unsigned offset);
>
> @@ -124,6 +132,11 @@ extern void gpio_set_value_cansleep(unsigned gpio, int value);
> */
> extern int __gpio_get_value(unsigned gpio);
> extern void __gpio_set_value(unsigned gpio, int value);
> +#ifdef CONFIG_GPIOLIB_BATCH
> +extern void __gpio_set_batch(unsigned gpio, u32 values, u32 bitmask,
> + int bitwidth);
> +extern u32 __gpio_get_batch(unsigned gpio, u32 bitmask, int bitwidth);
> +#endif
>
> extern int __gpio_cansleep(unsigned gpio);
>
> --
> 1.5.2.3
>
> --
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--
Cheers
- eric
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