[PATCH v2] gpiolib: fix allocation of mixed dynamic/static GPIOs

[Andreas Kemnade <andreas@kemnade.info>]

If static allocation and dynamic allocation GPIOs are present,
dynamic allocation pollutes the numberspace for static allocation,
causing static allocation to fail.
Enfore dynamic allocation above GPIO_DYNAMIC_BASE.

Seen on a GTA04 when omap-gpio (static) and twl-gpio (dynamic)
raced:
[some successful registrations of omap_gpio instances]
[    2.553833] twl4030_gpio twl4030-gpio: gpio (irq 145) chaining IRQs 161..178
[    2.561401] gpiochip_find_base: found new base at 160
[    2.564392] gpio gpiochip5: (twl4030): added GPIO chardev (254:5)
[    2.564544] gpio gpiochip5: registered GPIOs 160 to 177 on twl4030
[...]
[    2.692169] omap-gpmc 6e000000.gpmc: GPMC revision 5.0
[    2.697357] gpmc_mem_init: disabling cs 0 mapped at 0x0-0x1000000
[    2.703643] gpiochip_find_base: found new base at 178
[    2.704376] gpio gpiochip6: (omap-gpmc): added GPIO chardev (254:6)
[    2.704589] gpio gpiochip6: registered GPIOs 178 to 181 on omap-gpmc
[...]
[    2.840393] gpio gpiochip7: Static allocation of GPIO base is deprecated, use dynamic allocation.
[    2.849365] gpio gpiochip7: (gpio-160-191): GPIO integer space overlap, cannot add chip
[    2.857513] gpiochip_add_data_with_key: GPIOs 160..191 (gpio-160-191) failed to register, -16
[    2.866149] omap_gpio 48310000.gpio: error -EBUSY: Could not register gpio chip

On that device it is fixed invasively by
commit 92bf78b33b0b4 ("gpio: omap: use dynamic allocation of base")
but lets also fix that for devices where there is still
a mixture of static and dynamic allocation.

Fixes: 7b61212f2a07 ("gpiolib: Get rid of ARCH_NR_GPIOS")
Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
---
Changes in V2:
   handle also the case of overlapping static allocation
   across DYNAMIC_BASE

 drivers/gpio/gpiolib.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 19bd23044b017..4472214fcd43a 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -193,6 +193,8 @@ static int gpiochip_find_base(int ngpio)
 			break;
 		/* nope, check the space right after the chip */
 		base = gdev->base + gdev->ngpio;
+		if (base < GPIO_DYNAMIC_BASE)
+			base = GPIO_DYNAMIC_BASE;
 	}
 
 	if (gpio_is_valid(base)) {
-- 
2.39.2