[BHND/bcma] Add implementation of BHND_BUS_RESET_CORE function for BCMA

[mizhka]

Summary

This patch addes missing implementation of BHND_BUS_RESET_CORE function for BCMA. The reset procedure is very simple: enable reset mode, stop clocking, enable clocking & force clock gating, disable reset mode, stop clock gating.

Test Plan

Tested on ASUS RT-N53 for enabling/reset USB core

[adrian]

looks good!

[landonf]

In addition to inline comments, if you happen to feel like implementing the nearly identical bcma_suspend_core(), I wouldn't say no :-)

sys/dev/bhnd/bcma/bcma.c

220 ↗

(On Diff #17758)

To ensure there are no pending operations prior to putting the core in reset, you should spin here for 300ms (in 10us intervals) waiting for resetstatus to clear.

224 ↗

(On Diff #17758)

After this 10us delay, you should spin waiting for resetstatus to clear; the resetctrl read-back shouldn't be necessary.

229 ↗

(On Diff #17758)

I'd recommend a slightly different order of operations that leaves the clock enabled/stable during reset (not that there's any documentation for any of this stuff ...).

• Gate clock (SICF_FGC), but leave it enabled (SICF_CLOCK_EN).
• Take core out of reset by clearing resetctrl.
• Spin waiting for a read of resetctrl to return 0, retry up to ~10 times after first waiting up to 300us (in 10us intervals) for resetstatus to clear (for total possible delay of 3000us)
• Disable clock gating (clear SICF_FGC).

sys/dev/bhnd/bhnd_core.h

27 ↗

(On Diff #17758)

These bcma-specific register offsets and bitflags are defined in bcma_dmp.h; can you switch to using those?

The bhnd_core.h header is shared with siba(4), which has its own register offsets/layout, but uses most of the same flags (including core-specific flags).

BCMA Offsets:

• BHND_CF ->BCMA_DMP_IOCTRL (0x408)
• BHND_SF -> BCMA_DMP_IOSTATUS (0x500)
• BHND_RESET_CF -> BCMA_DMP_RESETCTRL (0x800)
• BHND_RESET_SF -> BCMA_DMP_RESETSTATUS (0x804)

BCMA Flags:

• BHND_RESET_CF_ENABLE -> BCMA_DMP_RC_RESET (0x0001)

[mizhka]

In D6920#145338, @landonf wrote:

In addition to inline comments, if you happen to feel like implementing the nearly identical bcma_suspend_core(), I wouldn't say no :-)

I can't find BCMA_DMP_RC_RESET:
https://github.com/freebsd/freebsd/search?utf8=%E2%9C%93&q=BCMA_DMP_RC_RESET&type=Code

Is there a typo?

[mizhka]

• usage of macros from bcma_dmp.h instead of new ones
• added status checks

Tested on Asus RT-N53 (USB core)

[adrian]

when you're both happy with it, I'll approve/commit it!

[mizhka]

• fixed typo in macro name
• timeout variable

[landonf]

It looks like the earlier revision already went in r302106. I can just revisit this when I get back around to implementing the siba versions and the remaining bcma suspend code.