Re: [PATCH 2/2] drivers/gpio: Port gpio driver to layerscape platform
From: Arnd Bergmann <arnd@arndb.de>
Date: 2015-11-04 08:53:13
Also in:
linux-arm-kernel, linux-gpio
On Wednesday 04 November 2015 14:48:24 Liu Gang wrote:
quoted hunk ↗ jump to hunk
Layerscape has the same ip block/controller as GPIO on powerpc platform(MPC8XXX). So use portable i/o accessors, as in_be32/out_be32 accessors are Power architecture specific whereas ioread32/iowrite32 and ioread32be/iowrite32be are available in other architectures. Layerscape GPIO controller's registers may be big or little endian, so the code needs to get the endian property from DTB, then make additional functions to fit right register read/write operations. Currently the code can support ls2080a GPIO with little endian registers. And it can also work well on other layerscape platform with big endian GPIO registers. Signed-off-by: Liu Gang <redacted> Signed-off-by: Shaveta Leekha <redacted>diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig index 8949b3f..c3ca283 100644 --- a/drivers/gpio/Kconfig +++ b/drivers/gpio/Kconfig@@ -290,12 +290,12 @@ config GPIO_MPC5200 depends on PPC_MPC52xx config GPIO_MPC8XXX - bool "MPC512x/MPC8xxx GPIO support" + bool "MPC512x/MPC8xxx/QorIQ GPIO support" depends on PPC_MPC512x || PPC_MPC831x || PPC_MPC834x || PPC_MPC837x || \ - FSL_SOC_BOOKE || PPC_86xx + FSL_SOC_BOOKE || PPC_86xx || ARCH_LAYERSCAPE help Say Y here if you're going to use hardware that connects to the - MPC512x/831x/834x/837x/8572/8610 GPIOs. + MPC512x/831x/834x/837x/8572/8610/QorIQ GPIOs.
It would be nice to also add '|| COMPILE_TEST' here and ensure that it also builds on x86 with that set, to get better coverage from the automated build testing infrastructure.
+static bool gpio_little_endian;
+static inline u32 gpio_in32(void __iomem *addr)
+{
+ u32 val;
+
+ if (gpio_little_endian)
+ val = ioread32(addr);
+ else
+ val = ioread32be(addr);
+
+ return val;
+}
+
+static inline void gpio_out32(u32 val, void __iomem *addr)
+{
+ if (gpio_little_endian)
+ iowrite32(val, addr);
+ else
+ iowrite32be(val, addr);
+}
I guess this is fixed per architecture, so you could also do this as
static inline void gpio_out32(u32 val, void __iomem *addr)
{
if (IS_ENABLED(CONFIG_ARM))
iowrite32(val, addr);
else if (IS_ENABLED(CONFIG_PPC)
iowrite32be(val, addr);
else
BUG();
}
and then check that the DT flag for little-endian matches
the architecture specific default.
Your version is more generic of course, while the one I show here
is a little more efficient and avoids the global variable. Your choice.
Arnd