Re: [PATCH v5 0/3] Support multiplexed main SMBus interface on SB800

[fetzerch <fetzer.ch@gmail.com>]

Hi Jean,

On 22.01.2016 13:50, Jean Delvare wrote:
> Hi Christian,
> 
> On Thu, 19 Nov 2015 20:13:46 +0100, Christian Fetzer wrote:
>> This is an attempt to upstream the patches created by Thomas Brandon and
>> Eddi De Pieri to support the multiplexed main SMBus interface on the SB800
>> chipset. (https://www.mail-archive.com/linux-i2c@vger.kernel.org/msg06757.html)
>>
>> I have mainly rebased the latest patch version and tested the driver on a
>> HP ProLiant MicroServer G7 N54L (where this patch allows to access sensor data
>> from a w83795adg).
>>
>> The patched driver is running stable on the machine, given that ic2_piix4 is
>> loaded before jc42 and w83795. If jc42 is loaded before i2c_piix4 calling
>> sensors triggers some errors:
>>     ERROR: Can't get value of subfeature temp1_min_alarm: Can't read
>>
>> While the kernel log shows:
>>     i2c i2c-1: Transaction (pre): CNT=0c, CMD=05, ADD=31, DAT0=03, DAT1=c0
>>     i2c i2c-1: Error: no response!
>>     i2c i2c-1: Transaction (post): CNT=0c, CMD=05, ADD=31, DAT0=ff, DAT1=ff
>> Unfortunately I don't know how to tackle this specific issue.
> 
> I think I can explain it. In piix4_setup_sb800() you touch the
> SB800_PIIX4_SMB_IDX port without first taking the mutex that protects
> it. You only take the mutex on transactions (in piix4_access_sb800) not
> during initialization. If self-probing I2C device drivers such as jc42
> are already loaded before you load i2c-piix4, then as soon as the first
> SMBus port is registered, i2c-core will try to attach I2C devices to
> it, while at the same time i2c-piix4 is registering the second SMBus
> port. So SB800_PIIX4_SMB_IDX is changed while piix4_access_sb800
> accesses it and chaos happens.
> 
> I think if we had proper locking in piix4_setup_sb800() then you should
> be able to load jc42 first and then i2c-piix4 and it should work fine.
> 

Since the problem remains even after your patch, I'll try to provide
more information about the issue.

If i2c_piix4 is loaded before jc42 and w83795 things work as they should
and sensors prints values from all modules.

If w83795 is loaded before i2c_piix4, the w83795adg is not detected. I'm
not sure though if this is because of i2c_piix4 or just a shortcoming in
the w83795 module.

If jc42 is loaded before i2c_piix4 then the problem described above
occurs. It seems that jc42 tries to read from all multiplexed ports.
This is the full sensors output:

jc42-i2c-0-18
Adapter: SMBus PIIX4 adapter SDA0 at 0b00
RAM1 Temp:    +26.8°C  (low  =  +0.0°C)
                       (high = +60.0°C, hyst = +54.0°C)
                       (crit = +70.0°C, hyst = +64.0°C)

jc42-i2c-0-19
Adapter: SMBus PIIX4 adapter SDA0 at 0b00
RAM2 Temp:    +26.5°C  (low  =  +0.0°C)
                       (high = +60.0°C, hyst = +54.0°C)
                       (crit = +70.0°C, hyst = +64.0°C)

k10temp-pci-00c3
Adapter: PCI adapter
CPU Temp:     +30.6°C  (high = +70.0°C)
                       (crit = +100.0°C, hyst = +95.0°C)

jc42-i2c-1-18
Adapter: SMBus PIIX4 adapter SDA2 at 0b00
ERROR: Can't get value of subfeature temp1_min_alarm: Can't read
ERROR: Can't get value of subfeature temp1_max_alarm: Can't read
ERROR: Can't get value of subfeature temp1_crit_alarm: Can't read
ERROR: Can't get value of subfeature temp1_min: Can't read
ERROR: Can't get value of subfeature temp1_max: Can't read
ERROR: Can't get value of subfeature temp1_max_hyst: Can't read
ERROR: Can't get value of subfeature temp1_crit: Can't read
ERROR: Can't get value of subfeature temp1_crit_hyst: Can't read
temp1:            N/A  (low  =  +0.0°C)
                       (high =  +0.0°C, hyst =  +0.0°C)
                       (crit =  +0.0°C, hyst =  +0.0°C)

jc42-i2c-1-19
Adapter: SMBus PIIX4 adapter SDA2 at 0b00
ERROR: Can't get value of subfeature temp1_min_alarm: Can't read
ERROR: Can't get value of subfeature temp1_max_alarm: Can't read
ERROR: Can't get value of subfeature temp1_crit_alarm: Can't read
ERROR: Can't get value of subfeature temp1_min: Can't read
ERROR: Can't get value of subfeature temp1_max: Can't read
ERROR: Can't get value of subfeature temp1_max_hyst: Can't read
ERROR: Can't get value of subfeature temp1_crit: Can't read
ERROR: Can't get value of subfeature temp1_crit_hyst: Can't read
temp1:            N/A  (low  =  +0.0°C)
                       (high =  +0.0°C, hyst =  +0.0°C)
                       (crit =  +0.0°C, hyst =  +0.0°C)

jc42-i2c-2-18
Adapter: SMBus PIIX4 adapter SDA3 at 0b00
ERROR: Can't get value of subfeature temp1_min_alarm: Can't read
ERROR: Can't get value of subfeature temp1_max_alarm: Can't read
ERROR: Can't get value of subfeature temp1_crit_alarm: Can't read
ERROR: Can't get value of subfeature temp1_min: Can't read
ERROR: Can't get value of subfeature temp1_max: Can't read
ERROR: Can't get value of subfeature temp1_max_hyst: Can't read
ERROR: Can't get value of subfeature temp1_crit: Can't read
ERROR: Can't get value of subfeature temp1_crit_hyst: Can't read
temp1:            N/A  (low  =  +0.0°C)
                       (high =  +0.0°C, hyst =  +0.0°C)
                       (crit =  +0.0°C, hyst =  +0.0°C)

jc42-i2c-2-19
Adapter: SMBus PIIX4 adapter SDA3 at 0b00
ERROR: Can't get value of subfeature temp1_min_alarm: Can't read
ERROR: Can't get value of subfeature temp1_max_alarm: Can't read
ERROR: Can't get value of subfeature temp1_crit_alarm: Can't read
ERROR: Can't get value of subfeature temp1_min: Can't read
ERROR: Can't get value of subfeature temp1_max: Can't read
ERROR: Can't get value of subfeature temp1_max_hyst: Can't read
ERROR: Can't get value of subfeature temp1_crit: Can't read
ERROR: Can't get value of subfeature temp1_crit_hyst: Can't read
temp1:            N/A  (low  =  +0.0°C)
                       (high =  +0.0°C, hyst =  +0.0°C)
                       (crit =  +0.0°C, hyst =  +0.0°C)

jc42-i2c-3-18
Adapter: SMBus PIIX4 adapter SDA4 at 0b00
ERROR: Can't get value of subfeature temp1_min_alarm: Can't read
ERROR: Can't get value of subfeature temp1_max_alarm: Can't read
ERROR: Can't get value of subfeature temp1_crit_alarm: Can't read
ERROR: Can't get value of subfeature temp1_min: Can't read
ERROR: Can't get value of subfeature temp1_max: Can't read
ERROR: Can't get value of subfeature temp1_max_hyst: Can't read
ERROR: Can't get value of subfeature temp1_crit: Can't read
ERROR: Can't get value of subfeature temp1_crit_hyst: Can't read
temp1:            N/A  (low  =  +0.0°C)
                       (high =  +0.0°C, hyst =  +0.0°C)
                       (crit =  +0.0°C, hyst =  +0.0°C)

jc42-i2c-3-19
Adapter: SMBus PIIX4 adapter SDA4 at 0b00
ERROR: Can't get value of subfeature temp1_min_alarm: Can't read
ERROR: Can't get value of subfeature temp1_max_alarm: Can't read
ERROR: Can't get value of subfeature temp1_crit_alarm: Can't read
ERROR: Can't get value of subfeature temp1_min: Can't read
ERROR: Can't get value of subfeature temp1_max: Can't read
ERROR: Can't get value of subfeature temp1_max_hyst: Can't read
ERROR: Can't get value of subfeature temp1_crit: Can't read
ERROR: Can't get value of subfeature temp1_crit_hyst: Can't read
temp1:            N/A  (low  =  +0.0°C)
                       (high =  +0.0°C, hyst =  +0.0°C)
                       (crit =  +0.0°C, hyst =  +0.0°C)