[coreboot] v3 smbus device structure
c-d.hailfinger.devel.2006 at gmx.net
Sat Feb 23 01:15:12 CET 2008
On 23.02.2008 00:34, Marc Jones wrote:
> Carl-Daniel Hailfinger wrote:
>> On 22.02.2008 22:02, Marc Jones wrote:
>>> We need to discuss v3 smbus operations. Someone has done a lot of
>>> work to make smbus_ops.c and smbus.h. The code treats smbus as a
>>> bus, like the pci bus, with a device structure and all.
>>> This approach seems nice and maybe the right way to do it, but it is
>>> somewhat overkill. I think that the complexity is one reason why the
>>> structure is in place in v2 but never used. Instead, simpler
>>> chipset/mainboard specific functions are used. The other reason is
>>> that the smbus is accessed in ROMCC/CAR code and not in the main
>>> coreboot bus enumeration code. My observation is that the SPD is the
>>> only device on smbus used by most mainboards in coreboot.
>>> So, what do we want to do for v3? If we go with the bus/device
>>> structure every mainboard in v2 will need to have the smbus
>>> functions ported. Also, someone will have to figure out how to
>>> describe the smbus devices in the dts and the entire thing might
>>> need to use a simpler bus/device structure. Or, we can do as was
>>> done in v2 and leave it to the chipset/mainboard code.
>> This is a bit more complicated than visible at first glance. We have
>> two different smbus_read_byte() functions in v3:
>> int smbus_read_byte(u16 device, u8 address);
>> int smbus_read_byte(struct device *dev, u8 addr);
>> The confusion arises because these two clearly different functions
>> have the same name. I'd suggest to rename the first smbus_read_byte
>> to smbus_read_byte_early to make it clear that it does not care about
>> the device tree. All initram stuff just uses the first function.
> That would work, but why have the device tree version if it is never
That may change in the future. We keep lots of code in v3 which is not
used yet. AGP, PCIE, CardBus etc.
Rename the non-devicetree version of smbus_read_byte() to
smbus_read_byte_early() to resolve a naming conflict.
Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006 at gmx.net>
--- LinuxBIOSv3-smbusreadbyte-rename/southbridge/amd/cs5536/smbus_initram.c (Revision 616)
+++ LinuxBIOSv3-smbusreadbyte-rename/southbridge/amd/cs5536/smbus_initram.c (Arbeitskopie)
@@ -319,7 +319,7 @@
* @param address The address.
* @return The data from the SMBus packet area or an error of 0xff (i.e. -1).
-int smbus_read_byte(u16 device, u8 address)
+int smbus_read_byte_early(u16 device, u8 address)
static int first_time = 1;
@@ -335,7 +335,7 @@
* Read a byte from the SPD.
* For this chip, that is really just saying 'read a byte from SMBus'.
- * So we use smbus_read_byte(). Nota Bene: leave this here as a function
+ * So we use smbus_read_byte_early(). Nota Bene: leave this here as a function
* rather than a #define in an obscure location. This function is called
* only a few dozen times, and it's not performance critical.
@@ -345,5 +345,5 @@
u8 spd_read_byte(u16 device, u8 address)
- return smbus_read_byte(device, address);
+ return smbus_read_byte_early(device, address);
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