lkml.org 
[lkml]   [2021]   [Mar]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: Errant readings on LM81 with T2080 SoC
From
Date
On 3/11/21 12:18 AM, Wolfram Sang wrote:
>
>> Bummer. What is really weird is that you see clock stretching under
>> CPU load. Normally clock stretching is triggered by the device, not
>> by the host.
>
> One example: Some hosts need an interrupt per byte to know if they
> should send ACK or NACK. If that interrupt is delayed, they stretch the
> clock.
>

Indeed, the i2c-mpc driver sends TXAK (only) after receiving
that interrupt. Since that is running in the context of the user
process, that may well be delayed substantially on a loaded system.

Maybe the interrupt handler will need to play a more active role
in the i2c-mpc driver. Alternatively, the transfer function could
be handled by a high priority kernel thread.

Guenter

[unhandled content-type:application/pgp-signature]
\
 
 \ /
  Last update: 2021-03-11 16:21    [W:0.080 / U:0.164 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site