remoteproc: add IOMMU hardware capability flag

The remoteproc framework currently relies on iommu_present() on
the bus the device is on, to perform MMU management. However, this
logic doesn't scale for multi-arch, especially for processors that
do not have an IOMMU. Replace this logic instead by using a h/w
capability flag for the presence of IOMMU in the rproc structure.

This issue is seen on OMAP platforms when trying to add a remoteproc
driver for a small Cortex M3 called the WkupM3 used for suspend /
resume management on TI AM335/AM437x SoCs. This processor does not
have an MMU. Same is the case with another processor subsystem
PRU-ICSS on AM335/AM437x. All these are platform devices, and the
current iommu_present check will not scale for the same kernel image
to support OMAP4/OMAP5 and AM335/AM437x.

The existing platform implementation drivers - OMAP remoteproc, STE
Modem remoteproc and DA8xx remoteproc, are updated as well to properly
configure the newly added rproc field.

Cc: Robert Tivy <rtivy@ti.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Suman Anna <s-anna@ti.com>
[small change in the commit title and in a single comment]
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>

drivers/remoteproc/da8xx_remoteproc.c

@@ -224,6 +224,7 @@ static int da8xx_rproc_probe(struct platform_device *pdev)
 
 	drproc = rproc->priv;
 	drproc->rproc = rproc;
+	rproc->has_iommu = false;
 
 	platform_set_drvdata(pdev, rproc);
 

drivers/remoteproc/omap_remoteproc.c

@@ -202,6 +202,8 @@ static int omap_rproc_probe(struct platform_device *pdev)
 
 	oproc = rproc->priv;
 	oproc->rproc = rproc;
+	/* All existing OMAP IPU and DSP processors have an MMU */
+	rproc->has_iommu = true;
 
 	platform_set_drvdata(pdev, rproc);
 

drivers/remoteproc/remoteproc_core.c

@@ -94,19 +94,8 @@ static int rproc_enable_iommu(struct rproc *rproc)
 	struct device *dev = rproc->dev.parent;
 	int ret;
 
-	/*
-	 * We currently use iommu_present() to decide if an IOMMU
-	 * setup is needed.
-	 *
-	 * This works for simple cases, but will easily fail with
-	 * platforms that do have an IOMMU, but not for this specific
-	 * rproc.
-	 *
-	 * This will be easily solved by introducing hw capabilities
-	 * that will be set by the remoteproc driver.
-	 */
-	if (!iommu_present(dev->bus)) {
-		dev_dbg(dev, "iommu not found\n");
+	if (!rproc->has_iommu) {
+		dev_dbg(dev, "iommu not present\n");
 		return 0;
 	}
 

drivers/remoteproc/ste_modem_rproc.c

@@ -289,6 +289,7 @@ static int sproc_probe(struct platform_device *pdev)
 	sproc = rproc->priv;
 	sproc->mdev = mdev;
 	sproc->rproc = rproc;
+	rproc->has_iommu = false;
 	mdev->drv_data = sproc;
 
 	/* Provide callback functions to modem device */

include/linux/remoteproc.h

@@ -404,6 +404,7 @@ enum rproc_crash_type {
  * @table_ptr: pointer to the resource table in effect
  * @cached_table: copy of the resource table
  * @table_csum: checksum of the resource table
+ * @has_iommu: flag to indicate if remote processor is behind an MMU
  */
 struct rproc {
 	struct klist_node node;
@@ -435,6 +436,7 @@ struct rproc {
 	struct resource_table *table_ptr;
 	struct resource_table *cached_table;
 	u32 table_csum;
+	bool has_iommu;
 };
 
 /* we currently support only two vrings per rvdev */