powerpc/xive: introduce xive_esb_write()

Some source support MMIO stores on the ESB page to perform EOI. Let's
introduce a specific routine for this case even if this should be the
only use of it.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/sysdev/xive/common.c

@@ -203,6 +203,15 @@ static notrace u8 xive_esb_read(struct xive_irq_data *xd, u32 offset)
 	return (u8)val;
 }
 
+static void xive_esb_write(struct xive_irq_data *xd, u32 offset, u64 data)
+{
+	/* Handle HW errata */
+	if (xd->flags & XIVE_IRQ_FLAG_SHIFT_BUG)
+		offset |= offset << 4;
+
+	out_be64(xd->eoi_mmio + offset, data);
+}
+
 #ifdef CONFIG_XMON
 static notrace void xive_dump_eq(const char *name, struct xive_q *q)
 {
@@ -297,7 +306,7 @@ void xive_do_source_eoi(u32 hw_irq, struct xive_irq_data *xd)
 {
 	/* If the XIVE supports the new "store EOI facility, use it */
 	if (xd->flags & XIVE_IRQ_FLAG_STORE_EOI)
-		out_be64(xd->eoi_mmio + XIVE_ESB_STORE_EOI, 0);
+		xive_esb_write(xd, XIVE_ESB_STORE_EOI, 0);
 	else if (hw_irq && xd->flags & XIVE_IRQ_FLAG_EOI_FW) {
 		/*
 		 * The FW told us to call it. This happens for some