[RESEND v2 RFC 0/5] Enhancements for mv64xxx I2C driver

[RESEND v2 RFC 0/5] Enhancements for mv64xxx I2C driver

[Sam Edwards]

Salutations, Linux I2C team!

Apologies again for another resend; I'm just as surprised as you all that
modern email clients are so hostile to sending the exact byte-for-byte .mbox
given to them. Really wishing I could use git-send-email and be done with it.
But, third time's the charm!

I am working with an Allwinner T113-s3 based board; the internal I2C bus of
which has a Realtek RTL8370MB-CG Ethernet switch coexisting with other I2C
devices. The RTL8370MB-CG deviates from "conventional" I2C read operations
in that it expects the hardware register after the addr+read byte before it
turns around the bus to send the value. For this reason, the `realtek-smi`
driver currently implements the protocol via bit-banging. However, I am in the
process of developing a separate patch series to promote this driver to a
"full" I2C driver, leveraging I2C_M_NOSTART to support this odd read operation.

In anticipation of that, I am preparing this series comprising five patches to
improve the functionality and reliability of the I2C adapter enough to support
this kind of device. I have heavily tested these changes on the Allwinner-style
mv64xxx core, but not the Marvell-style, and have not been able to test 10-bit
addressing. I would greatly appreciate if anyone here could test this series,
especially on non-Allwinner boards and/or boards with 10-bit devices.

I'm a bit skeptical of using I2C_M_NOSTART for this purpose. The driver does
not (and cannot) support "just any" use of I2C_M_NOSTART, so it may be
inappropriate to claim the I2C_FUNC_NOSTART capability. On the other hand, I
searched high and low and couldn't find any use of I2C_M_NOSTART that
*wouldn't* be supported by this change, so this could very well be exactly what
clients understand I2C_FUNC_NOSTART to mean. Given that the alternative would
be inventing a new flag ("I2C_M_READEXTRA"?) and figuring out how to supply
input bytes and output bytes in the same i2c_msg, I opted for the NOSTART
route instead.

I look forward to any feedback, bug reports, test results, questions, concerns,
commentary, or discussion that you can offer!

Best regards,
Sam

Sam Edwards (5):
  i2c: mv64xxx: Clear bus errors before transfer
  i2c: mv64xxx: Clean up the private data struct
  i2c: mv64xxx: Refactor FSM
  i2c: mv64xxx: Allow continuing after read
  i2c: mv64xxx: Implement I2C_FUNC_NOSTART

 drivers/i2c/busses/i2c-mv64xxx.c | 430 ++++++++++++++++++++++---------
 1 file changed, 302 insertions(+), 128 deletions(-)

-- 
2.43.2

Re: [RESEND v2 RFC 0/5] Enhancements for mv64xxx I2C driver

[Andi Shyti]

Hi Gregory,

On Tue, Mar 19, 2024 at 06:44:56PM -0600, Sam Edwards wrote:
> Salutations, Linux I2C team!

...

> In anticipation of that, I am preparing this series comprising five patches to
> improve the functionality and reliability of the I2C adapter enough to support
> this kind of device. I have heavily tested these changes on the Allwinner-style
> mv64xxx core, but not the Marvell-style, and have not been able to test 10-bit
> addressing. I would greatly appreciate if anyone here could test this series,
> especially on non-Allwinner boards and/or boards with 10-bit devices.
> 
> I'm a bit skeptical of using I2C_M_NOSTART for this purpose. The driver does
> not (and cannot) support "just any" use of I2C_M_NOSTART, so it may be
> inappropriate to claim the I2C_FUNC_NOSTART capability. On the other hand, I
> searched high and low and couldn't find any use of I2C_M_NOSTART that
> *wouldn't* be supported by this change, so this could very well be exactly what
> clients understand I2C_FUNC_NOSTART to mean. Given that the alternative would
> be inventing a new flag ("I2C_M_READEXTRA"?) and figuring out how to supply
> input bytes and output bytes in the same i2c_msg, I opted for the NOSTART
> route instead.

any thought on this series? I believe here we might need a bit
more testing on other platforms.

Andi

> 
> I look forward to any feedback, bug reports, test results, questions, concerns,
> commentary, or discussion that you can offer!
> 
> Best regards,
> Sam
> 
> Sam Edwards (5):
>   i2c: mv64xxx: Clear bus errors before transfer
>   i2c: mv64xxx: Clean up the private data struct
>   i2c: mv64xxx: Refactor FSM
>   i2c: mv64xxx: Allow continuing after read
>   i2c: mv64xxx: Implement I2C_FUNC_NOSTART

Re: [RESEND v2 RFC 0/5] Enhancements for mv64xxx I2C driver

[Gregory CLEMENT]

Hello Andi and Sam,

> Hi Gregory,
>
> On Tue, Mar 19, 2024 at 06:44:56PM -0600, Sam Edwards wrote:
>> Salutations, Linux I2C team!
>
> ...
>
>> In anticipation of that, I am preparing this series comprising five patches to
>> improve the functionality and reliability of the I2C adapter enough to support
>> this kind of device. I have heavily tested these changes on the Allwinner-style
>> mv64xxx core, but not the Marvell-style, and have not been able to test 10-bit
>> addressing. I would greatly appreciate if anyone here could test this series,
>> especially on non-Allwinner boards and/or boards with 10-bit devices.
>> 
>> I'm a bit skeptical of using I2C_M_NOSTART for this purpose. The driver does
>> not (and cannot) support "just any" use of I2C_M_NOSTART, so it may be
>> inappropriate to claim the I2C_FUNC_NOSTART capability. On the other hand, I
>> searched high and low and couldn't find any use of I2C_M_NOSTART that
>> *wouldn't* be supported by this change, so this could very well be exactly what
>> clients understand I2C_FUNC_NOSTART to mean. Given that the alternative would
>> be inventing a new flag ("I2C_M_READEXTRA"?) and figuring out how to supply
>> input bytes and output bytes in the same i2c_msg, I opted for the NOSTART
>> route instead.
>
> any thought on this series? I believe here we might need a bit
> more testing on other platforms.

Sorry for the lack of answer. However I saw the series, I will have a
closer look on it and give you feednacks.

Regards,

Gregory

>
> Andi
>
>> 
>> I look forward to any feedback, bug reports, test results, questions, concerns,
>> commentary, or discussion that you can offer!
>> 
>> Best regards,
>> Sam
>> 
>> Sam Edwards (5):
>>   i2c: mv64xxx: Clear bus errors before transfer
>>   i2c: mv64xxx: Clean up the private data struct
>>   i2c: mv64xxx: Refactor FSM
>>   i2c: mv64xxx: Allow continuing after read
>>   i2c: mv64xxx: Implement I2C_FUNC_NOSTART