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Re: 8250 memory mapped UART

From: Gailu Singh
Subject: Re: 8250 memory mapped UART
Date: Wed, 1 Mar 2017 16:02:39 +0530

I checked coreboot where in the memory it is mapped and it seems to be on PCIE. Relevant code from coreboot. So I am hopeful that patch will work.
uintptr_t uart_platform_base(int idx)
u8      *pcie;
u32      tmp;
idx  = idx & 3;
pcie = (u8 *)PCIE_MMIO(0, PCH_DEV_SLOT_UART, idx, 0);
tmp  = read32 (pcie + PCI_BASE_ADDRESS_0);
if (tmp == 0xFFFFFFFF) {
/* the device might be hidden */
} else {
return (uintptr_t) (tmp & 0xFFFFFFF0);

 I applied the patches and run make clean followed by make but build failed as follows
cat syminfo.lst | sort | gawk -f ./genmoddep.awk > moddep.lst || (rm -f moddep.lst; exit 1)
grub_ns8250_pci_mmio_init in serial is not defined
make[3]: *** [moddep.lst] Error 1

On Wed, Mar 1, 2017 at 3:27 PM, Gailu Singh <address@hidden> wrote:
Sorry for typo. I meant 8250 instead of 8050 in last email

On Wed, Mar 1, 2017 at 3:21 PM, Gailu Singh <address@hidden> wrote:
My board is Intel Oxbohill CRB (Apollo lake). On my board UART are not connected to PCI. 

I am using grub2 payload loaded by coreboot. UART works fine in coreboot by using memory mapped 8050 driver (, however when grub2 is loaded it refuses to recognize UART.

On Wed, Mar 1, 2017 at 3:08 PM, Matthias Lange <address@hiddenm> wrote:

On 03/01/2017 08:00 AM, Andrei Borzenkov wrote:
> please test patches from Matthias Lange
> On Wed, Mar 1, 2017 at 9:15 AM, Gailu Singh <address@hidden> wrote:
>> Hi Experts,
>> I am using GRUB2 on intel apollo lake board. This board does not have IO
>> mapped uart instead it has 8250 memory mapped UART.

Could you share some details about the board?

>> GRUB2 does not recognize memory mapped uart and gives error ("serial port
>> COM0 not found). There is a 8250 memory mapped driver available in coreboot.
>> Is it possible to port that driver to Grub2?

My patch set adds support for 8250 MMIO PCI cards. Is the UART on your
board connected via PCI?


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