[U-Boot] [PATCH 4/5] x86: Support PCI UART in the x86_serial driver

[Bin Meng]

Hi Simon,

On Sat, Dec 20, 2014 at 5:52 AM, Simon Glass <sjg at chromium.org> wrote:
> Hi BIn,
>
> On 19 December 2014 at 00:19, Bin Meng <bmeng.cn at gmail.com> wrote:
>> Newer x86 Platform Controller Hub chipset starts to integrate NS16550
>> compatible PCI UART devices. The board configuration file needs to
>> supply the PCI UART vendor ID and device ID via CONFIG_PCI_UART_DEV
>> if we want to use the PCI UART as the U-Boot serial console.
>>
>> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
>> ---
>>
>>  drivers/serial/serial_x86.c | 30 ++++++++++++++++++++++++++++++
>>  1 file changed, 30 insertions(+)
>>
>> diff --git a/drivers/serial/serial_x86.c b/drivers/serial/serial_x86.c
>> index e81e035..7ddd596 100644
>> --- a/drivers/serial/serial_x86.c
>> +++ b/drivers/serial/serial_x86.c
>> @@ -8,6 +8,17 @@
>>  #include <dm.h>
>>  #include <ns16550.h>
>>  #include <serial.h>
>> +#include <asm/pci.h>
>> +#include <errno.h>
>> +
>> +DECLARE_GLOBAL_DATA_PTR;
>> +
>> +#ifdef CONFIG_PCI_UART
>> +static struct pci_device_id uart_supported[] = {
>> +       CONFIG_PCI_UART_DEV,
>> +       { }
>> +};
>> +#endif
>>
>>  static const struct udevice_id x86_serial_ids[] = {
>>         { .compatible = "x86-uart" },
>> @@ -17,6 +28,9 @@ static const struct udevice_id x86_serial_ids[] = {
>>  static int x86_serial_ofdata_to_platdata(struct udevice *dev)
>>  {
>>         struct ns16550_platdata *plat = dev_get_platdata(dev);
>> +#ifdef CONFIG_PCI_UART
>> +       pci_dev_t devbusfn;
>> +#endif
>>         int ret;
>>
>>         ret = ns16550_serial_ofdata_to_platdata(dev);
>> @@ -24,6 +38,22 @@ static int x86_serial_ofdata_to_platdata(struct udevice *dev)
>>                 return ret;
>>         plat->clock = 1843200;
>>
>> +#ifdef CONFIG_PCI_UART
>> +       /*
>> +        * Newer x86 Platform Controller Hub chipset starts to integrate
>> +        * NS16550 compatible PCI UART devices. The board configuration
>> +        * file needs to supply the PCI UART vendor ID and device ID via
>> +        * CONFIG_PCI_UART_DEV if we want to use the PCI UART as the U-Boot
>> +        * serial console.
>> +        */
>> +       devbusfn = pci_early_find_devices(uart_supported, 0);
>> +       if (devbusfn == -1)
>> +               return -ENODEV;
>
> I'm not sure why we need this. Is it because we don't know the device
> address of the UART?
>

Yes, the UART device is not on the host bridge (bus 0). It is on the
PCH which is connected to the one of the downstream PCIe port of the
host bridge. Which PCIe port is used is determined by the board
designer. So that on my Crown Bay board the UART is on b.d.f 2.10.1
may become b.d.f 3.10.1 on some other queensbay platform board.
Actually the pci_find_devices() is a standard way to locate the
device's b.d.f, as you see in many PCI ethernet drivers in U-Boot. You
have no way to figure out the device will be inserted to which PCI
slot on the board.

[snip]

Regards,
Bin