tree 734de780e0f84a189f66ca3cbf611e6f2bc563e9
parent 1d16b0f2f3edf05f12a9e3960588e0d4854157bb
author Thomas Gleixner <tglx@linutronix.de> 1271165496 +0200
committer H. Peter Anvin <hpa@zytor.com> 1272503669 -0700

x86, hpet: Restrict read back to affected ATI chipsets

After programming the HPET, we do a readback as a workaround for
ATI/SBx00 chipsets as a synchronization.  Unfortunately this triggers
an erratum in newer ICH chipsets (ICH9+) where reading the comparator
immediately after the write returns the old value.  Furthermore, as
always, I/O reads are bad for performance.

Therefore, restrict the readback to the chipsets that need it, or, for
debugging purposes, when we are running with hpet=verbose.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Venkatesh Pallipadi <venki@google.com>
LKML-Reference: <20100225185348.GA9674@linux-os.sc.intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>