[U-Boot] [PATCH v2 5/7] rpi: Properly detect which serial device is active

[Simon Glass]

Hi Alex,

On 17 January 2018 at 15:05, Alexander Graf <agraf at suse.de> wrote:
>
>
> On 17.01.18 20:46, Simon Glass wrote:
>> Hi Alex,
>>
>> On 17 January 2018 at 00:54, Alexander Graf <agraf at suse.de> wrote:
>>> Now that we have all infrastructure in place to dynamically determine whether
>>> a serial device is actually usable (read: routed to user accessible pins), we
>>> can wire it up to the board.
>>>
>>> This patch adds support to determine whether the pl011 or mini-uart or no serial
>>> is routed to the UART RX/TX pins on the Raspberry Pi family of boards.
>>>
>>> Signed-off-by: Alexander Graf <agraf at suse.de>
>>> ---
>>>  board/raspberrypi/rpi/rpi.c | 69 +++++++++++++++++++++++++++++++++++++++++++++
>>>  1 file changed, 69 insertions(+)
>>>
>>> diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
>>> index a96d5d8952..b0cdad70f7 100644
>>> --- a/board/raspberrypi/rpi/rpi.c
>>> +++ b/board/raspberrypi/rpi/rpi.c
>>> @@ -24,9 +24,16 @@
>>>  #include <asm/armv8/mmu.h>
>>>  #endif
>>>  #include <watchdog.h>
>>> +#include <asm/io.h>
>>>
>>>  DECLARE_GLOBAL_DATA_PTR;
>>>
>>> +/*
>>> + * This is the GPIO pin that the user facing UART RX line is attached to.
>>> + * We use this pin to determine which serial device is available.
>>> + */
>>> +#define BCM2835_GPIO_RX                15
>>> +
>>>  /* From lowlevel_init.S */
>>>  extern unsigned long fw_dtb_pointer;
>>>
>>> @@ -419,6 +426,68 @@ static void get_board_rev(void)
>>>         printf("RPI %s (0x%x)\n", model->name, revision);
>>>  }
>>>
>>> +/*
>>> + * We may get called before the device model is initialized, so we can not
>>> + * rely on the GPIO driver.
>>> + */
>>> +int get_func_id(unsigned gpio)
>>> +{
>>> +       u32 val;
>>> +       u32 node;
>>> +       u32 *gpfsel;
>>> +       fdt_addr_t addr;
>>> +       fdt_size_t size;
>>> +
>>> +       node = fdt_node_offset_by_compatible(gd->fdt_blob, -1, "brcm,bcm2835-gpio");
>>> +       if (node < 0)
>>> +               return -EINVAL;
>>> +
>>> +       addr = fdtdec_get_addr_size_auto_noparent(gd->fdt_blob, node, "reg",
>>> +                                                 0, &size, true);
>>> +       gpfsel = (void*)addr;
>>> +
>>> +       val = readl(&gpfsel[BCM2835_GPIO_FSEL_BANK(gpio)]);
>>> +
>>> +       return (val >> BCM2835_GPIO_FSEL_SHIFT(gpio) & BCM2835_GPIO_FSEL_MASK);
>>> +}
>>
>> Ick, this should be done in the GPIO driver and use gpio_get_function().
>
> Yes, but what if users specify the serial device to be pre-reloc and
> don't do that for the GPIO (or really pinctrl) one? Then we'd not have
> the driver around to determine whether serial is active, right?

We have control of that in the DT so just need to set it up correctly.
I suppose worst case you could add the pre-reloc flag to each driver's
decl instead of in DT. But I'm not sure why the DT would be wrong.

Regards,
Simon