[rv_dm] Support non-word bus access

[jrrk2]

It seems that JTAG access via system bus only supports word access on Ibex, can you confirm?

[tomeroberts]

Yes that looks to be the case. Not sure why it's hardwired that way, but there is currently a PR open to add support for other sizes in the debug module repo (here).

[jrrk2]

Hi Tom, That patch seems to work well. Recommended if you want to use SEGGER Jlink rather than openocd/Olimex Regards, Jonathan

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On 26 Jan 2021, at 14:59, Tom Roberts ***@***.***> wrote:  Yes that looks to be the case. Not sure why it's hardwired that way, but there is currently a PR open to add support for other sizes in the debug module repo (here). — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub, or unsubscribe.

[imphil]

Just a quick update here: Segger J-Link V6.94c+ (05 Feb 2021) now works if only word accesses are provided according to lowRISC/ibex#1218 (comment).

[msfschaffner]

I have the feeling that this is not strictly required for the first revision, and would recommend to label this as a future enhancement that we can vendor in once the patch mentioned above has landed upstream. What do others think?

[sriyerg]

Agreed, as long as it is clearly documented in the spec.

[rswarbrick]

Sounds good to me.

[msfschaffner]

Support for this has been merged upstream: pulp-platform/riscv-dbg#106.

However, there is a fix for a CDC bug outstanding here pulp-platform/riscv-dbg#123 and I would recommend to wait for that one to land before we vendor in anything.

[msfschaffner]

Closing this issue since it is a duplicate.
Updates will be tracked here from now on: #11095.