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    cxl: Fix bug where AFU disable operation had no effect · 5e7823c9
    Ian Munsie 提交于
    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: NIan Munsie <imunsie@au1.ibm.com>
    Reviewed-by: NFrederic Barrat <fbarrat@linux.vnet.ibm.com>
    Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
    5e7823c9
cxl.h 32.5 KB