irqchip/ls-scfg-msi: Don't map the MSI page in ls_scfg_msi_compose_msg()

ls_scfg_msi_compose_msg() may be called from non-preemptible context.
However, on RT, iommu_dma_map_msi_msg() requires to be called from a
preemptible context.

A recent patch split iommu_dma_map_msi_msg() in two new functions:
one that should be called in preemptible context, the other does
not have any requirement.

The FreeScale SCFG MSI driver is reworked to avoid executing preemptible
code in non-preemptible context. This can be achieved by preparing the
MSI maping when allocating the MSI interrupt.
Signed-off-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/irqchip/irq-ls-scfg-msi.c

@@ -100,7 +100,7 @@ static void ls_scfg_msi_compose_msg(struct irq_data *data, struct msi_msg *msg)
 		msg->data |= cpumask_first(mask);
 	}
 
-	iommu_dma_map_msi_msg(data->irq, msg);
+	iommu_dma_compose_msi_msg(irq_data_get_msi_desc(data), msg);
 }
 
 static int ls_scfg_msi_set_affinity(struct irq_data *irq_data,
@@ -141,6 +141,7 @@ static int ls_scfg_msi_domain_irq_alloc(struct irq_domain *domain,
 					unsigned int nr_irqs,
 					void *args)
 {
+	msi_alloc_info_t *info = args;
 	struct ls_scfg_msi *msi_data = domain->host_data;
 	int pos, err = 0;
 
@@ -154,6 +155,10 @@ static int ls_scfg_msi_domain_irq_alloc(struct irq_domain *domain,
 		err = -ENOSPC;
 	spin_unlock(&msi_data->lock);
 
+	if (err)
+		return err;
+
+	err = iommu_dma_prepare_msi(info->desc, msi_data->msiir_addr);
 	if (err)
 		return err;