On 05/08/14 23:10, Piotr Król wrote:
> On Wed, May 07, 2014 at 10:22:06AM +0200, Paolo Bonzini wrote:
>>
>> What Laszlo said is correct. In PIIX4, the SMBus registers are not in a
>> BAR, instead you can read the base I/O address in the PCI configuration
>> space of the device at 00:01.3, bytes 0x90...0x91 (bit 0 is 1 for I/O
>> space). Writing 0x9 at byte 0xd2 of the configuration space enables it,
>> so from Linux you'd have:
>>
>> $ setpci -s 01.3 0x90.w
>> 0xb101
>>
>> 0xb100 is the default, but it can be changed.
>>
>> Because they're not in a BAR you probably need to access them directly
>> without using the PCI support in UEFI. You can use PCI support routines
>> to access the configuration space.
>>
>
> Laszlo, Paolo,
> thank you for reply. I will try to implement UEFI application to read
> temperature sensor in OVMF. I saw some I2cDxe and I2c protocol code so
> will investigate that.
It doesn't seem easy.
>From a cursory look, the by-the-book solution would be:
- Write a driver that implements the following three protocols for the
QEMU i2c hardware:
- EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL
MdePkg/Include/Protocol/I2cBusConfigurationManagement.h
- EFI_I2C_MASTER_PROTOCOL
MdePkg/Include/Protocol/I2cMaster.h
- EFI_I2C_ENUMERATE_PROTOCOL
MdePkg/Include/Protocol/I2cEnumerate.h
- Include this new driver in the OVMF build (DSC, FDF files).
- Include "MdeModulePkg/Bus/I2c/I2cDxe/I2cDxe.inf" too. What happens is
EFI_I2C_BUS_CONFIGURATION_MANAGEMENT_PROTOCOL EFI_I2C_MASTER_PROTOCOL
\ /
EFI_I2C_ENUMERATE_PROTOCOL EFI_I2C_HOST_PROTOCOL (by I2cHost.c)
\ /
EFI_I2C_IO_PROTOCOL (by I2cBus.c)
- Write an application that locates handles that have an
EFI_I2C_IO_PROTOCOL interface, identifies the one device that you
care about, and communicates with it.
It's probably much simpler to go for an app that accesses ports directly.
Laszlo
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