On Sun, 11 Sep 2011 11:50:09 +0200, Michal Zatloukal wrote: > On Sun, 11 Sep 2011 10:09:45 +0200, Jean Delvare <khali@xxxxxxxxxxxx> > wrote: > > > Hi Michal, > > ... > > Second preliminary note: as far as I know, memtest86 reads SPD > > information using a BIOS call, while decode-dimms gets the information > > over the SMBus, assuming that SPD EEPROMs are connected to the SMBus > > and reachable at run time. This difference in access methods can > > explain why memtest86 can see information and decode-dimms not on the > > same system. > > Is there a way to do the BIOS call method in Linux? If it's a sort-of > standard way to access SPD info, would it be the one used by CPU-Z to read > the SPD info on Windows? (which does work on this HW) I am not so familiar with this. I seem to recall that BIOS calls are not easy/safe to use in protected mode on x86, so it might be difficult or even impossible to do that from user-space. From kernel space, maybe, I don't know. It is very possible that it's what CPU-Z is doing. However I don't know if the author is willing to share his method. A quick web search did not return anything, but I admit I did not spend too much time on it, and I am also not so sure what I am looking for. If anyone ever writes a kernel driver exposing SPD data to user-space, I will be very happy to update decode-dimms to take benefit of that. > > First thing to check is if the SMBus on your system is properly found > > and supported: > > > > # modprobe i2c-dev > > # i2cdetect -l > > > > On an Intel system you should see an entry like: > > > > i2c-8 smbus SMBus I801 adapter at 0400 SMBus adapter > > Nope. On 'buntu 10.10, I only got 5 entries (didn't write them down), none > of which said smbus. On 11.10, I get: > > # i2cdetect -l > i2c-0 i2c i915 gmbus disabled I2C adapter > i2c-1 i2c i915 gmbus ssc I2C adapter > i2c-2 i2c i915 GPIOB I2C adapter > i2c-3 i2c i915 gmbus vga I2C adapter > i2c-4 i2c i915 GPIOA I2C adapter > i2c-5 i2c i915 gmbus panel I2C adapter > i2c-6 i2c i915 GPIOC I2C adapter > i2c-7 i2c i915 gmbus dpc I2C adapter > i2c-8 i2c i915 GPIOD I2C adapter > i2c-9 i2c i915 gmbus dpb I2C adapter > i2c-10 i2c i915 GPIOE I2C adapter > i2c-11 i2c i915 gmbus reserved I2C adapter > i2c-12 i2c i915 gmbus dpd I2C adapter > i2c-13 i2c i915 GPIOF I2C adapter > i2c-14 i2c SDVO DDC proxy I2C adapter > > And BTW, this is the same list I get on my "server/router/AP" (Intel > D945GSEJT nettop board running 'buntu 11.04) which is also in the same > situation (can't read SPD info). No SMBus I801 adapter. Is the i2c-i801 driver loaded? Do you see any complaints in the kernel log (e.g. ACPI resource conflict) when reloading the i2c-i801 driver? > > Then you can check if devices are seen on the bus: > > > > # i2cdetect 8 > > > > If you see anything in address range 0x50 to 0x55, this is likely to be > > SPD EEPROMs. Then you have to make sure that the eeprom module is > > loaded: > > From the above list, buses 3-6 have a value 0x50 at 0x50 like so: > # i2cdetect -y 5 > 0 1 2 3 4 5 6 7 8 9 a b c d e f > <snip> > 50: 50 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- > > Though that's probably irrelevant, as it's not the SMBus, if I understand > correctly. Most likely the EDID from your screen, you can decode it with: # modprobe eeprom $ decode-edid But that's not what your are looking for. -- Jean Delvare -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
