2013-06-21 18:22:12

by Simon Pearson

Subject: [PATCH 001/001] gpio-mxs: Select faster gpio-generic set methods

From: Simon Pearson <[email protected]>

Kernel 3.8.4. By defining both the set and clear registers,
the speed of the gpio isimproved. gpio-generic.c, selects the
bgpio_set_with_clear() which isfaster than the current
bgpio_set_set(). This has performance implications for all
bitbang drivers (i2c, spi, etc). Slow SPI as compared to
2.6.35.33 improved by a factor of 10 (80kHz CLK to 800kHz CLK).

Signed-off-by: Simon Pearson <[email protected]>

---
--- a/drivers/gpio/gpio-mxs.c.orig 2013-03-20 13:11:19.000000000 -0700
+++ b/drivers/gpio/gpio-mxs.c 2013-06-21 10:02:33.000000000 -0700
@@ -292,7 +292,8 @@ static int mxs_gpio_probe(struct platfor

err = bgpio_init(&port->bgc, &pdev->dev, 4,
port->base + PINCTRL_DIN(port),
- port->base + PINCTRL_DOUT(port), NULL,
+ port->base + PINCTRL_DOUT(port) + MXS_SET,
+ port->base + PINCTRL_DOUT(port) + MXS_CLR,
port->base + PINCTRL_DOE(port), NULL, 0);
if (err)
goto out_irqdesc_free;

2013-06-24 06:59:16

by Shawn Guo

Subject: Re: [PATCH 001/001] gpio-mxs: Select faster gpio-generic set methods

On Fri, Jun 21, 2013 at 11:14:07AM -0700, Simon Pearson wrote:
> From: Simon Pearson <[email protected]>
>
> Kernel 3.8.4. By defining both the set and clear registers,
> the speed of the gpio isimproved. gpio-generic.c, selects the
> bgpio_set_with_clear() which isfaster than the current
> bgpio_set_set(). This has performance implications for all
> bitbang drivers (i2c, spi, etc). Slow SPI as compared to
> 2.6.35.33 improved by a factor of 10 (80kHz CLK to 800kHz CLK).
>
> Signed-off-by: Simon Pearson <[email protected]>

The latest mainline kernel already has the improvement made by commit
90dae4e (gpio: mxs: Use set and clear capabilities of the gpio
controller).

Shawn

>
> ---
> --- a/drivers/gpio/gpio-mxs.c.orig 2013-03-20 13:11:19.000000000 -0700
> +++ b/drivers/gpio/gpio-mxs.c 2013-06-21 10:02:33.000000000 -0700
> @@ -292,7 +292,8 @@ static int mxs_gpio_probe(struct platfor
>
> err = bgpio_init(&port->bgc, &pdev->dev, 4,
> port->base + PINCTRL_DIN(port),
> - port->base + PINCTRL_DOUT(port), NULL,
> + port->base + PINCTRL_DOUT(port) + MXS_SET,
> + port->base + PINCTRL_DOUT(port) + MXS_CLR,
> port->base + PINCTRL_DOE(port), NULL, 0);
> if (err)
> goto out_irqdesc_free;