[v2] cxl: Fix bug where AFU disable operation had no effect

[Michael Ellerman]

On Thu, 2016-30-06 at 16:50:40 UTC, Ian Munsie wrote:
> From: Ian Munsie <imunsie at au1.ibm.com>
> 
> The AFU disable operation has a bug where it will not clear the enable
> bit and therefore will have no effect. To date this has likely been
> masked by fact that we perform an AFU reset before the disable, which
> also has the effect of clearing the enable bit, making the following
> disable operation effectively a noop on most hardware. This patch
> modifies the afu_control function to take a parameter to clear from the
> AFU control register so that the disable operation can clear the
> appropriate bit.
> 
> This bug was uncovered on the Mellanox CX4, which uses an XSL rather
> than a PSL. On the XSL the reset operation will not complete while the
> AFU is enabled, meaning the enable bit was still set at the start of the
> disable and as a result this bug was hit and the disable also timed out.
> 
> Because of this difference in behaviour between the PSL and XSL, this
> patch now makes the reset dependent on the card using a PSL to avoid
> waiting for a timeout on the XSL. It is entirely possible that we may be
> able to drop the reset altogether if it turns out we only ever needed it
> due to this bug - however I am not willing to drop it without further
> regression testing and have added comments to the code explaining the
> background.
> 
> This also fixes a small issue where the AFU_Cntl register was read
> outside of the lock that protects it.
> 
> Signed-off-by: Ian Munsie <imunsie at au1.ibm.com>
> Reviewed-by: Frederic Barrat <fbarrat at linux.vnet.ibm.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/5e7823c9bc44965c2e7d1d755b

cheers