Hello i2c gurus,

I have a machine which has the AT24C64C eeprom chip, I have been trying to write to it via i2c and have been having issues on CentOS5.3 as well as "Red Hat Enterprise Linux Server release 6.0 Beta (Santiago)". I can write to the EEPROM succesfully when I use Ubuntu10.04LTS as well as upstream kernel v2.6.35 compiled from source on the same machine.

While looking for patches, I came accross https://bugzilla.redhat.com/show_bug.cgi?id=182687 and adding an extra delay in the piix4_transaction function fixes the problem for me as well.

Also it seems that the read operation to the chip succeeds, its only the write that fails consistently. If I try writes in a loop, it succeeds once in about 10-13 tries.

I think the problems are related, but any pointers would be appreciated. I am pasting information about my machine, please let me know if you guys needs any more information

Thanks
--Munir

Steps to repro:
==============
To test I have been using the eeprog program (http://codesink.org/eeprog.html)
Execute the following command to write to eeprom
[root@localhost eeprog-0.7.6]# echo "MMMMMM" | ./eeprog -16 -w 0x0 /dev/i2c-0 0x51 -f
eeprog 0.7.6, a 24Cxx EEPROM reader/writer
Copyright (c) 2003-2004 by Stefano Barbato - All rights reserved.
   Bus: /dev/i2c-0, Address: 0x51, Mode: 16bit
   Writing stdin starting at address 0x0
..Error i2c_write_3b: No such device or address
Error at line 150: write error



Information about the server:
============================
[root@localhost eeprog-0.7.6]# lsmod
Module                  Size  Used by
i2c_dev                 8697  0
autofs4                27683  3
nfs                   348825  8
lockd                  73984  1 nfs
fscache                46761  1 nfs
nfs_acl                 2677  1 nfs
auth_rpcgss            44862  1 nfs
sunrpc                241694  27 nfs,lockd,nfs_acl,auth_rpcgss
cpufreq_ondemand       10382  8
powernow_k8            16298  1
freq_table              4847  2 cpufreq_ondemand,powernow_k8
ipv6                  320850  54
dm_mirror              14003  0
dm_region_hash         12200  1 dm_mirror
dm_log                 10088  2 dm_mirror,dm_region_hash
edac_core              46087  0
edac_mce_amd            8949  0
i2c_piix4              12574  0
i2c_core               31274  2 i2c_dev,i2c_piix4
sg                     30154  0
shpchp                 33448  0
e1000e                137118  0
ext3                  133453  3
jbd                    54576  1 ext3
mbcache                 7918  1 ext3
sd_mod                 36960  5
crc_t10dif              1507  1 sd_mod
ata_generic             3611  0
pata_acpi               3667  0
pata_atiixp             4177  0
ahci                   38859  4
mpt2sas               151535  0
scsi_transport_sas     35036  1 mpt2sas
raid_class              4738  1 mpt2sas
dm_mod                 74162  2 dm_mirror,dm_log

[root@localhost eeprog-0.7.6]# lspci -nvv -s 00:14.0
00:14.0 0c05: 1002:4385 (rev 3d)
	Subsystem: 1002:4385
	Control: I/O+ Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx+
	Status: Cap+ 66MHz+ UDF- FastB2B- ParErr- DEVSEL=medium>TAbort-<TAbort-<MAbort->SERR-<PERR- INTx-
	Capabilities: [b0] HyperTransport: MSI Mapping Enable- Fixed+
	Kernel driver in use: piix4_smbus
	Kernel modules: i2c-piix4
[root@localhost eeprog-0.7.6]# lspci
00:00.0 Host bridge: ATI Technologies Inc RD890 Northbridge only dual slot (2x16) PCI-e GFX Hydra part (rev 02)
00:04.0 PCI bridge: ATI Technologies Inc RD890 PCI to PCI bridge (PCI express gpp port D)
00:05.0 PCI bridge: ATI Technologies Inc RD890 PCI to PCI bridge (PCI express gpp port E)
00:06.0 PCI bridge: ATI Technologies Inc RD890 PCI to PCI bridge (PCI express gpp port F)
00:07.0 PCI bridge: ATI Technologies Inc RD890 PCI to PCI bridge (PCI express gpp port G)
00:09.0 PCI bridge: ATI Technologies Inc RD890 PCI to PCI bridge (PCI express gpp port H)
00:0a.0 PCI bridge: ATI Technologies Inc RD890 PCI to PCI bridge (external gfx1 port A)
00:0c.0 PCI bridge: ATI Technologies Inc Device 5a20
00:0d.0 PCI bridge: ATI Technologies Inc RD890 PCI to PCI bridge (external gfx1 port B)
00:11.0 SATA controller: ATI Technologies Inc SB700/SB800 SATA Controller [AHCI mode]
00:12.0 USB Controller: ATI Technologies Inc SB700/SB800 USB OHCI0 Controller
00:12.1 USB Controller: ATI Technologies Inc SB700 USB OHCI1 Controller
00:12.2 USB Controller: ATI Technologies Inc SB700/SB800 USB EHCI Controller
00:13.0 USB Controller: ATI Technologies Inc SB700/SB800 USB OHCI0 Controller
00:13.1 USB Controller: ATI Technologies Inc SB700 USB OHCI1 Controller
00:13.2 USB Controller: ATI Technologies Inc SB700/SB800 USB EHCI Controller
00:14.0 SMBus: ATI Technologies Inc SBx00 SMBus Controller (rev 3d)
00:14.1 IDE interface: ATI Technologies Inc SB700/SB800 IDE Controller
00:14.3 ISA bridge: ATI Technologies Inc SB700/SB800 LPC host controller
00:14.4 PCI bridge: ATI Technologies Inc SBx00 PCI to PCI Bridge
00:14.5 USB Controller: ATI Technologies Inc SB700/SB800 USB OHCI2 Controller
00:18.0 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] HyperTransport Configuration
00:18.1 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Address Map
00:18.2 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] DRAM Controller
00:18.3 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Miscellaneous Control
00:18.4 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Link Control
00:19.0 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] HyperTransport Configuration
00:19.1 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Address Map
00:19.2 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] DRAM Controller
00:19.3 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Miscellaneous Control
00:19.4 Host bridge: Advanced Micro Devices [AMD] K10 [Opteron, Athlon64, Sempron] Link Control
02:00.0 PCI bridge: ASPEED Technology, Inc. Device 1150 (rev 02)
03:00.0 VGA compatible controller: ASPEED Technology, Inc. ASPEED Graphics Family (rev 10)
04:00.0 Serial Attached SCSI controller: LSI Logic / Symbios Logic SAS2008 PCI-Express Fusion-MPT SAS-2 [Falcon] (rev 03)
05:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection
06:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection
07:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection
08:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection
09:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection
0a:00.0 Ethernet controller: Intel Corporation 82574L Gigabit Network Connection
40:00.0 Host bridge: ATI Technologies Inc RD890 PCI to PCI bridge (external gfx0 port A) (rev 02)

[root@localhost eeprog-0.7.6]# uname -a
Linux localhost.localdomain 2.6.32-37.el6.x86_64 #1 SMP Sun Jun 20 19:29:35 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux
[root@localhost eeprog-0.7.6]# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 6.0 Beta (Santiago)