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

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Date:	Fri, 21 Jun 2013 11:14:07 -0700
From:	Simon Pearson <spearson@...malabs.com>
To:	grant.likely@...retlab.ca, linus.walleij@...aro.org
CC:	shawn.guo@...aro.org, linux-kernel@...r.kernel.org
Subject: [PATCH 001/001] gpio-mxs: Select faster gpio-generic set methods

From: Simon Pearson <spearson@...malabs.com>

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 <spearson@...malabs.com>

---
--- 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;
--
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