remoteproc: add a rproc ops for performing address translation

The rproc_da_to_va API is currently used to perform any device to
kernel address translations to meet the different needs of the remoteproc
core/drivers (eg: loading). The functionality is achieved within the
remoteproc core, and is limited only for carveouts allocated within the
core.

A new rproc ops, da_to_va, is added to provide flexibility to platform
implementations to perform the address translation themselves when the
above conditions cannot be met by the implementations. The rproc_da_to_va()
API is extended to invoke this ops if present, and fallback to regular
processing if the platform implementation cannot provide the translation.
This will allow any remoteproc implementations to translate addresses for
dedicated memories like internal memories.

While at this, also update the rproc_da_to_va() documentation since it
is an exported function.

Signed-off-by: Suman Anna <[e-mail]>
Signed-off-by: Dave Gerlach <[e-mail]>
Signed-off-by: Ohad Ben-Cohen <[e-mail]>

drivers/remoteproc/remoteproc_core.c

···
 	iommu_domain_free(domain);
 }
 
-/*
+/**
+ * rproc_da_to_va() - lookup the kernel virtual address for a remoteproc address
+ * @rproc: handle of a remote processor
+ * @da: remoteproc device address to translate
+ * @len: length of the memory region @da is pointing to
+ *
  * Some remote processors will ask us to allocate them physically contiguous
  * memory regions (which we call "carveouts"), and map them to specific
- * device addresses (which are hardcoded in the firmware).
+ * device addresses (which are hardcoded in the firmware). They may also have
+ * dedicated memory regions internal to the processors, and use them either
+ * exclusively or alongside carveouts.
  *
  * They may then ask us to copy objects into specific device addresses (e.g.
  * code/data sections) or expose us certain symbols in other device address
  * (e.g. their trace buffer).
  *
- * This function is an internal helper with which we can go over the allocated
- * carveouts and translate specific device address to kernel virtual addresses
- * so we can access the referenced memory.
+ * This function is a helper function with which we can go over the allocated
+ * carveouts and translate specific device addresses to kernel virtual addresses
+ * so we can access the referenced memory. This function also allows to perform
+ * translations on the internal remoteproc memory regions through a platform
+ * implementation specific da_to_va ops, if present.
+ *
+ * The function returns a valid kernel address on success or NULL on failure.
  *
  * Note: phys_to_virt(iommu_iova_to_phys(rproc->domain, da)) will work too,
  * but only on kernel direct mapped RAM memory. Instead, we're just using
- * here the output of the DMA API, which should be more correct.
+ * here the output of the DMA API for the carveouts, which should be more
+ * correct.
  */
 void *rproc_da_to_va(struct rproc *rproc, u64 da, int len)
 {
 	struct rproc_mem_entry *carveout;
 	void *ptr = NULL;
+
+	if (rproc->ops->da_to_va) {
+		ptr = rproc->ops->da_to_va(rproc, da, len);
+		if (ptr)
+			goto out;
+	}
 
 	list_for_each_entry(carveout, &rproc->carveouts, node) {
 		int offset = da - carveout->da;
···
 		break;
 	}
 
+out:
 	return ptr;
 }
 EXPORT_SYMBOL(rproc_da_to_va);

include/linux/remoteproc.h

···
  * @start:	power on the device and boot it
  * @stop:	power off the device
  * @kick:	kick a virtqueue (virtqueue id given as a parameter)
+ * @da_to_va:	optional platform hook to perform address translations
  */
 struct rproc_ops {
 	int (*start)(struct rproc *rproc);
 	int (*stop)(struct rproc *rproc);
 	void (*kick)(struct rproc *rproc, int vqid);
+	void * (*da_to_va)(struct rproc *rproc, u64 da, int len);
 };
 
 /**