gpio/nomadik: support low EMI mode

Low EMI (Electro-Magnetic Interference) mode means lower slew
rate on the signals. The Nomadik GPIO controller supports
this so create an interface to enable it.

Signed-off-by: Rabin Vincent <rabin.vincent@stericsson.com>
Reviewed-by: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

1 files changed, 25 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-nomadik.c b/drivers/gpio/gpio-nomadik.c
index 681daee80291..7b45d88b4f44 100644
--- a/drivers/gpio/gpio-nomadik.c
+++ b/drivers/gpio/gpio-nomadik.c
@@ -61,6 +61,7 @@ struct nmk_gpio_chip {
         u32 rimsc;
         u32 fimsc;
         u32 pull_up;
+        u32 lowemi;
 };
 
 static struct nmk_gpio_chip *
@@ -125,6 +126,24 @@ static void __nmk_gpio_set_pull(struct nmk_gpio_chip *nmk_chip,
         }
 }
 
+static void __nmk_gpio_set_lowemi(struct nmk_gpio_chip *nmk_chip,
+                                  unsigned offset, bool lowemi)
+{
+        u32 bit = BIT(offset);
+        bool enabled = nmk_chip->lowemi & bit;
+
+        if (lowemi == enabled)
+                return;
+
+        if (lowemi)
+                nmk_chip->lowemi |= bit;
+        else
+                nmk_chip->lowemi &= ~bit;
+
+        writel_relaxed(nmk_chip->lowemi,
+                       nmk_chip->addr + NMK_GPIO_LOWEMI);
+}
+
 static void __nmk_gpio_make_input(struct nmk_gpio_chip *nmk_chip,
                                   unsigned offset)
 {
@@ -269,6 +288,8 @@ static void __nmk_config_pin(struct nmk_gpio_chip *nmk_chip, unsigned offset,
                 __nmk_gpio_set_pull(nmk_chip, offset, pull);
         }
 
+        __nmk_gpio_set_lowemi(nmk_chip, offset, PIN_LOWEMI(cfg));
+
         /*
          * If the pin is switching to altfunc, and there was an interrupt
          * installed on it which has been lazy disabled, actually mask the
@@ -1181,6 +1202,10 @@ static int __devinit nmk_gpio_probe(struct platform_device *dev)
         chip->dev = &dev->dev;
         chip->owner = THIS_MODULE;
 
+        clk_enable(nmk_chip->clk);
+        nmk_chip->lowemi = readl_relaxed(nmk_chip->addr + NMK_GPIO_LOWEMI);
+        clk_disable(nmk_chip->clk);
+
         ret = gpiochip_add(&nmk_chip->chip);
         if (ret)
                 goto out_free;