powerpc/pseries: Add kernel parameter to disable batched hcalls

This introduces a pair of kernel parameters that can be used to disable
the MULTITCE and BULK_REMOVE h-calls.

By default, those hcalls are enabled, active, and good for throughput
and performance.  The ability to disable them will be useful for some of
the PREEMPT_RT related investigation and work occurring on Power.

Signed-off-by: Will Schmidt <will_schmidt@vnet.ibm.com>
cc: Olof Johansson <olof@lixom.net>
cc: Anton Blanchard <anton@samba.org>
cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 14 insertions, 0 deletions

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index a77bcaed80a..fa2906a103d 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -622,3 +622,17 @@ void iommu_init_early_pSeries(void)
 	set_pci_dma_ops(&dma_iommu_ops);
 }
 
+static int __init disable_multitce(char *str)
+{
+	if (strcmp(str, "off") == 0 &&
+	    firmware_has_feature(FW_FEATURE_LPAR) &&
+	    firmware_has_feature(FW_FEATURE_MULTITCE)) {
+		printk(KERN_INFO "Disabling MULTITCE firmware feature\n");
+		ppc_md.tce_build = tce_build_pSeriesLP;
+		ppc_md.tce_free	 = tce_free_pSeriesLP;
+		powerpc_firmware_features &= ~FW_FEATURE_MULTITCE;
+	}
+	return 1;
+}
+
+__setup("multitce=", disable_multitce);