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Commit 99c3ce33 authored by Alistair Popple's avatar Alistair Popple Committed by Michael Ellerman
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powerpc/powernv/npu: Add a debugfs setting to change ATSD threshold 



The threshold at which it becomes more efficient to coalesce a range
of ATSDs into a single per-PID ATSD is currently not well understood
due to a lack of real-world work loads. This patch adds a debugfs
parameter allowing the threshold to be altered at runtime in order to
aid future development and refinement of the value.

Signed-off-by: default avatarAlistair Popple <alistair@popple.id.au>
Acked-by: default avatarBalbir Singh <bsingharora@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent d69ccc00

arch/powerpc/platforms/powernv/npu-dma.c

+10 −2
Original line number Diff line number Diff line
@@ -17,7 +17,9 @@ 
#include <linux/pci.h>

#include <linux/memblock.h>

#include <linux/iommu.h>

#include <linux/debugfs.h>



#include <asm/debugfs.h>

#include <asm/tlb.h>

#include <asm/powernv.h>

#include <asm/reg.h>
@@ -44,7 +46,8 @@ static DEFINE_SPINLOCK(npu_context_lock); 
 * entire TLB on the GPU for the given PID rather than each specific address in

 * the range.

 */

#define ATSD_THRESHOLD (2*1024*1024)

static uint64_t atsd_threshold = 2 * 1024 * 1024;

static struct dentry *atsd_threshold_dentry;



/*

 * Other types of TCE cache invalidation are not functional in the
@@ -683,7 +686,7 @@ static void pnv_npu2_mn_invalidate_range(struct mmu_notifier *mn, 
	struct npu_context *npu_context = mn_to_npu_context(mn);

	unsigned long address;



	if (end - start > ATSD_THRESHOLD) {

	if (end - start > atsd_threshold) {

		/*

		 * Just invalidate the entire PID if the address range is too

		 * large.
@@ -958,6 +961,11 @@ int pnv_npu2_init(struct pnv_phb *phb) 
	static int npu_index;

	uint64_t rc = 0;



	if (!atsd_threshold_dentry) {

		atsd_threshold_dentry = debugfs_create_x64("atsd_threshold",

				   0600, powerpc_debugfs_root, &atsd_threshold);

	}



	phb->npu.nmmu_flush =

		of_property_read_bool(phb->hose->dn, "ibm,nmmu-flush");

	for_each_child_of_node(phb->hose->dn, dn) {