Linux Kernel JTAG Support

[Dhananjay Phadke]

On 4/25/2022 3:45 PM, Derek Mantey wrote:
> It looks like there was a discussion a while back (~2017) about adding a Kernel driver for JTAG devices.  We are looking at using this for a variety of scenarios like OpenOCD and FW update for CPLD/FPGA components.  I was hoping to get some insight into the current status of the JTAG drivers and if there was anyone working on it.
> 
> The patches I saw from 2017 were: https://patchwork.ozlabs.org/project/openbmc/list/?series=18558&state=%2A&archive=both
> 
> Additionally, it looks like there are multiple implementations that exist:
>    1. Facebook: https://github.com/facebook/openbmc-linux/commits/dev-5.6/drivers/jtag
>    2. Aspeed: https://github.com/AspeedTech-BMC/linux/commits/aspeed-master-v5.15/drivers/jtag >    3. Ampere: 
https://github.com/ampere-openbmc/linux/commits/ampere/drivers/jtag
> 
> It looks like these have different version of the driver with slight differences in the interface.
> 
>    1. What is current status of the JTAG driver?  Is anyone still actively working on getting this pushed into the upstream kernel?
> 	a. Was there pushback from the Linux Kernel on taking these changes?
> 	b. If the upstream Kernel doesn't want to take these changes, would we consider having them in the https://github.com/openbmc/linux fork?
>    2. Does the community have a "preferred" JTAG driver that they are working on?  I am not sure how much people are sharing the changes to JTAG.  Is there a "best" driver to start from?
>    3. Are there any other people working on or looking at the JTAG driver?  I would like to know what others are doing so that we can align ideas and requirements, and not re-implement if possible.
> 
> Thanks,
> 	Derek

v29 looks to be the last upstream post by Intel -
https://lore.kernel.org/all/20200413222920.4722-1-ernesto.corona@intel.com/T/#u

v31 coming soon?
https://lore.kernel.org/all/DM6PR11MB399360880403A83FFECD597D8B769@DM6PR11MB3993.namprd11.prod.outlook.com/