From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marek Vasut Date: Thu, 20 Jun 2013 22:16:21 +0200 Subject: [U-Boot] [PATCH] gpio: spear_gpio: Fix gpio_set_value() implementation In-Reply-To: <51C35FC9.8040205@amarulasolutions.com> References: <1371712419.4200.1.camel@phoenix> <51C35FC9.8040205@amarulasolutions.com> Message-ID: <201306202216.21994.marex@denx.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Dear Michael Trimarchi, > Hi > > On 06/20/2013 03:56 PM, Axel Lin wrote: > > 2013/6/20 Marek Vasut > > > >> Dear Axel Lin, > >> > >>> In current gpio_set_value() implementation, it always sets the gpio > >>> control bit no matter the value argument is 0 or 1. Thus the GPIOs > >>> never set to low. This patch fixes this bug. > >>> > >>> Signed-off-by: Axel Lin > >>> --- > >>> > >>> drivers/gpio/spear_gpio.c | 5 ++++- > >>> 1 file changed, 4 insertions(+), 1 deletion(-) > >>> > >>> diff --git a/drivers/gpio/spear_gpio.c b/drivers/gpio/spear_gpio.c > >>> index d3c728e..8878608 100644 > >>> --- a/drivers/gpio/spear_gpio.c > >>> +++ b/drivers/gpio/spear_gpio.c > >>> @@ -52,7 +52,10 @@ int gpio_set_value(unsigned gpio, int value) > >>> > >>> { > >>> > >>> struct gpio_regs *regs = (struct gpio_regs *)CONFIG_GPIO_BASE; > >>> > >>> - writel(1 << gpio, ®s->gpiodata[DATA_REG_ADDR(gpio)]); > >>> + if (value) > >>> + writel(1 << gpio, ®s->gpiodata[DATA_REG_ADDR(gpio)]); > >>> + else > >>> + writel(0, ®s->gpiodata[DATA_REG_ADDR(gpio)]); > >> > >> How can this possibly work? Writing 0 to the whole bank will unset all > >> the GPIOs, no ? > > > > Because each GPIO is controlled by a register. > > And only one bit will be set when set gpio to high. > > Yes, but how to reset just one bit if you use the same register offset? > > I don't know this core but I know two possibilities: > > 1) one set register and one clear register > if (enable) > writel(1 << gpio, REGSET_BANK(gpio)); > else > writel(1 << gpio, REGCLEAR_BANK(gpio)); > 2) or > set operation > reg = readl(REG(gpio); > if (enable) > reg |= 1 << gpio; > else > reg &= ~(1 << gpio); > writel(reg, REG(GPIO)); > > Any other way? I think it's about time to read the datasheet :b Best regards, Marek Vasut