powerpc/vas, nx-842: Define and use chip_to_vas_id()

Define a helper, chip_to_vas_id() to map a given chip id to corresponding
vas id.

Normally, callers of vas_rx_win_open() and vas_tx_win_open() want the VAS
window to be on the same chip where the calling thread is executing. These
callers can pass in -1 for the VAS id.

This interface will be useful if a thread running on one chip wants to open
a window on another chip (like the NX-842 driver does during start up).

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

2 files changed, 20 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/vas.h b/arch/powerpc/include/asm/vas.h
index fd5963acd658..044748f547f5 100644
--- a/arch/powerpc/include/asm/vas.h
+++ b/arch/powerpc/include/asm/vas.h
@@ -104,6 +104,15 @@ struct vas_tx_win_attr {
 };
 
 /*
+ * Helper to map a chip id to VAS id.
+ * For POWER9, this is a 1:1 mapping. In the future this maybe a 1:N
+ * mapping in which case, we will need to update this helper.
+ *
+ * Return the VAS id or -1 if no matching vasid is found.
+ */
+int chip_to_vas_id(int chipid);
+
+/*
  * Helper to initialize receive window attributes to defaults for an
  * NX window.
  */
diff --git a/arch/powerpc/platforms/powernv/vas.c b/arch/powerpc/platforms/powernv/vas.c
index abb7090a22b4..cd9a733d05e2 100644
--- a/arch/powerpc/platforms/powernv/vas.c
+++ b/arch/powerpc/platforms/powernv/vas.c
@@ -123,6 +123,17 @@ struct vas_instance *find_vas_instance(int vasid)
 	return NULL;
 }
 
+int chip_to_vas_id(int chipid)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		if (cpu_to_chip_id(cpu) == chipid)
+			return per_cpu(cpu_vas_id, cpu);
+	}
+	return -1;
+}
+
 static int vas_probe(struct platform_device *pdev)
 {
 	return init_vas_instance(pdev);