Subject: [PATCH RESEND 0/6 v10] gpio: Add block GPIO

From: [email-masked] (Roland Stigge)
Date: Mon, 17 Dec 2012 14:51:58 +0100

Hi Wolfgang,

On 12/17/2012 02:32 PM, Roland Stigge wrote:
> And I guess Russell is right: If possible, we should write outputs
> simultaneously via ODSR (plus OWER/OWDR/OWSR) instead of separate set/clear.
> 
> I wonder if we need to save/restore the state of OWSR at every write
> operation or if we need/can cache it. Assuming that block GPIO are the
> only code in the kernel that manipulates ODSR.

Can you please test the following:

+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;
+
+       __raw_writel(~mask, pio + PIO_OWDR);
+       __raw_writel(mask, pio + PIO_OWER);
+       __raw_writel(val, pio + PIO_ODSR);
+}

Would caching OWSR be a significant speedup here?

Thanks in advance,

Roland