remoteproc: pru: Add support for PRU specific interrupt configuration

The firmware blob can contain optional ELF sections: .resource_table
section and .pru_irq_map one. The second one contains the PRUSS
interrupt mapping description, which needs to be setup before powering
on the PRU core. To avoid RAM wastage this ELF section is not mapped to
any ELF segment (by the firmware linker) and therefore is not loaded to
PRU memory.

The PRU interrupt configuration is handled within the PRUSS INTC irqchip
driver and leverages the system events to interrupt channels and host
interrupts mapping configuration. Relevant irq routing information is
passed through a special .pru_irq_map ELF section (for interrupts routed
to and used by PRU cores) or via the PRU application's device tree node
(for interrupts routed to and used by the main CPU). The mappings are
currently programmed during the booting/shutdown of the PRU.

The interrupt configuration passed through .pru_irq_map ELF section is
optional. It varies on specific firmware functionality and therefore
have to be unwinded during PRU stop and performed again during
PRU start.

Reviewed-by: Mathieu Poirier <[e-mail]>
Co-developed-by: Suman Anna <[e-mail]>
Signed-off-by: Suman Anna <[e-mail]>
Signed-off-by: Grzegorz Jaszczyk <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bjorn Andersson <[e-mail]>

drivers/remoteproc/pru_rproc.c

···
  */
 
 #include <linux/bitops.h>
+#include <linux/irqdomain.h>
 #include <linux/module.h>
 #include <linux/of_device.h>
+#include <linux/of_irq.h>
 #include <linux/pruss_driver.h>
 #include <linux/remoteproc.h>
 
 #include "remoteproc_internal.h"
 #include "remoteproc_elf_helpers.h"
+#include "pru_rproc.h"
 
 /* PRU_ICSS_PRU_CTRL registers */
 #define PRU_CTRL_CTRL		0x0000
···
 #define PRU_SDRAM_DA	0x2000	/* Secondary Data RAM */
 #define PRU_SHRDRAM_DA	0x10000 /* Shared Data RAM */
 
+#define MAX_PRU_SYS_EVENTS 160
+
 /**
  * enum pru_iomem - PRU core memory/register range identifiers
  *
···
  * @rproc: remoteproc pointer for this PRU core
  * @mem_regions: data for each of the PRU memory regions
  * @fw_name: name of firmware image used during loading
+ * @mapped_irq: virtual interrupt numbers of created fw specific mapping
+ * @pru_interrupt_map: pointer to interrupt mapping description (firmware)
+ * @pru_interrupt_map_sz: pru_interrupt_map size
+ * @evt_count: number of mapped events
  */
 struct pru_rproc {
 	int id;
···
 	struct rproc *rproc;
 	struct pruss_mem_region mem_regions[PRU_IOMEM_MAX];
 	const char *fw_name;
+	unsigned int *mapped_irq;
+	struct pru_irq_rsc *pru_interrupt_map;
+	size_t pru_interrupt_map_sz;
+	u8 evt_count;
 };
 
 static inline u32 pru_control_read_reg(struct pru_rproc *pru, unsigned int reg)
···
 	writel_relaxed(val, pru->mem_regions[PRU_IOMEM_CTRL].va + reg);
 }
 
+static void pru_dispose_irq_mapping(struct pru_rproc *pru)
+{
+	while (pru->evt_count--) {
+		if (pru->mapped_irq[pru->evt_count] > 0)
+			irq_dispose_mapping(pru->mapped_irq[pru->evt_count]);
+	}
+
+	kfree(pru->mapped_irq);
+}
+
+/*
+ * Parse the custom PRU interrupt map resource and configure the INTC
+ * appropriately.
+ */
+static int pru_handle_intrmap(struct rproc *rproc)
+{
+	struct device *dev = rproc->dev.parent;
+	struct pru_rproc *pru = rproc->priv;
+	struct pru_irq_rsc *rsc = pru->pru_interrupt_map;
+	struct irq_fwspec fwspec;
+	struct device_node *irq_parent;
+	int i, ret = 0;
+
+	/* not having pru_interrupt_map is not an error */
+	if (!rsc)
+		return 0;
+
+	/* currently supporting only type 0 */
+	if (rsc->type != 0) {
+		dev_err(dev, "unsupported rsc type: %d\n", rsc->type);
+		return -EINVAL;
+	}
+
+	if (rsc->num_evts > MAX_PRU_SYS_EVENTS)
+		return -EINVAL;
+
+	if (sizeof(*rsc) + rsc->num_evts * sizeof(struct pruss_int_map) !=
+	    pru->pru_interrupt_map_sz)
+		return -EINVAL;
+
+	pru->evt_count = rsc->num_evts;
+	pru->mapped_irq = kcalloc(pru->evt_count, sizeof(unsigned int),
+				  GFP_KERNEL);
+	if (!pru->mapped_irq)
+		return -ENOMEM;
+
+	/*
+	 * parse and fill in system event to interrupt channel and
+	 * channel-to-host mapping
+	 */
+	irq_parent = of_irq_find_parent(pru->dev->of_node);
+	if (!irq_parent) {
+		kfree(pru->mapped_irq);
+		return -ENODEV;
+	}
+
+	fwspec.fwnode = of_node_to_fwnode(irq_parent);
+	fwspec.param_count = 3;
+	for (i = 0; i < pru->evt_count; i++) {
+		fwspec.param[0] = rsc->pru_intc_map[i].event;
+		fwspec.param[1] = rsc->pru_intc_map[i].chnl;
+		fwspec.param[2] = rsc->pru_intc_map[i].host;
+
+		dev_dbg(dev, "mapping%d: event %d, chnl %d, host %d\n",
+			i, fwspec.param[0], fwspec.param[1], fwspec.param[2]);
+
+		pru->mapped_irq[i] = irq_create_fwspec_mapping(&fwspec);
+		if (!pru->mapped_irq[i]) {
+			dev_err(dev, "failed to get virq\n");
+			ret = pru->mapped_irq[i];
+			goto map_fail;
+		}
+	}
+
+	return ret;
+
+map_fail:
+	pru_dispose_irq_mapping(pru);
+
+	return ret;
+}
+
 static int pru_rproc_start(struct rproc *rproc)
 {
 	struct device *dev = &rproc->dev;
 	struct pru_rproc *pru = rproc->priv;
 	u32 val;
+	int ret;
 
 	dev_dbg(dev, "starting PRU%d: entry-point = 0x%llx\n",
 		pru->id, (rproc->bootaddr >> 2));
+
+	ret = pru_handle_intrmap(rproc);
+	/*
+	 * reset references to pru interrupt map - they will stop being valid
+	 * after rproc_start returns
+	 */
+	pru->pru_interrupt_map = NULL;
+	pru->pru_interrupt_map_sz = 0;
+	if (ret)
+		return ret;
 
 	val = CTRL_CTRL_EN | ((rproc->bootaddr >> 2) << 16);
 	pru_control_write_reg(pru, PRU_CTRL_CTRL, val);
···
 	val = pru_control_read_reg(pru, PRU_CTRL_CTRL);
 	val &= ~CTRL_CTRL_EN;
 	pru_control_write_reg(pru, PRU_CTRL_CTRL, val);
+
+	/* dispose irq mapping - new firmware can provide new mapping */
+	if (pru->mapped_irq)
+		pru_dispose_irq_mapping(pru);
 
 	return 0;
 }
···
 	return ret;
 }
 
+static const void *
+pru_rproc_find_interrupt_map(struct device *dev, const struct firmware *fw)
+{
+	struct elf32_shdr *shdr, *name_table_shdr;
+	const char *name_table;
+	const u8 *elf_data = fw->data;
+	struct elf32_hdr *ehdr = (struct elf32_hdr *)elf_data;
+	u16 shnum = ehdr->e_shnum;
+	u16 shstrndx = ehdr->e_shstrndx;
+	int i;
+
+	/* first, get the section header */
+	shdr = (struct elf32_shdr *)(elf_data + ehdr->e_shoff);
+	/* compute name table section header entry in shdr array */
+	name_table_shdr = shdr + shstrndx;
+	/* finally, compute the name table section address in elf */
+	name_table = elf_data + name_table_shdr->sh_offset;
+
+	for (i = 0; i < shnum; i++, shdr++) {
+		u32 size = shdr->sh_size;
+		u32 offset = shdr->sh_offset;
+		u32 name = shdr->sh_name;
+
+		if (strcmp(name_table + name, ".pru_irq_map"))
+			continue;
+
+		/* make sure we have the entire irq map */
+		if (offset + size > fw->size || offset + size < size) {
+			dev_err(dev, ".pru_irq_map section truncated\n");
+			return ERR_PTR(-EINVAL);
+		}
+
+		/* make sure irq map has at least the header */
+		if (sizeof(struct pru_irq_rsc) > size) {
+			dev_err(dev, "header-less .pru_irq_map section\n");
+			return ERR_PTR(-EINVAL);
+		}
+
+		return shdr;
+	}
+
+	dev_dbg(dev, "no .pru_irq_map section found for this fw\n");
+
+	return NULL;
+}
+
 /*
  * Use a custom parse_fw callback function for dealing with PRU firmware
  * specific sections.
+ *
+ * The firmware blob can contain optional ELF sections: .resource_table section
+ * and .pru_irq_map one. The second one contains the PRUSS interrupt mapping
+ * description, which needs to be setup before powering on the PRU core. To
+ * avoid RAM wastage this ELF section is not mapped to any ELF segment (by the
+ * firmware linker) and therefore is not loaded to PRU memory.
  */
 static int pru_rproc_parse_fw(struct rproc *rproc, const struct firmware *fw)
 {
+	struct device *dev = &rproc->dev;
+	struct pru_rproc *pru = rproc->priv;
+	const u8 *elf_data = fw->data;
+	const void *shdr;
+	u8 class = fw_elf_get_class(fw);
+	u64 sh_offset;
 	int ret;
 
 	/* load optional rsc table */
···
 		dev_dbg(&rproc->dev, "no resource table found for this fw\n");
 	else if (ret)
 		return ret;
+
+	/* find .pru_interrupt_map section, not having it is not an error */
+	shdr = pru_rproc_find_interrupt_map(dev, fw);
+	if (IS_ERR(shdr))
+		return PTR_ERR(shdr);
+
+	if (!shdr)
+		return 0;
+
+	/* preserve pointer to PRU interrupt map together with it size */
+	sh_offset = elf_shdr_get_sh_offset(class, shdr);
+	pru->pru_interrupt_map = (struct pru_irq_rsc *)(elf_data + sh_offset);
+	pru->pru_interrupt_map_sz = elf_shdr_get_sh_size(class, shdr);
 
 	return 0;
 }

drivers/remoteproc/pru_rproc.h

···
+/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-3-Clause) */
+/*
+ * PRUSS Remote Processor specific types
+ *
+ * Copyright (C) 2014-2020 Texas Instruments Incorporated - https://www.ti.com/
+ *	Suman Anna <[e-mail]>
+ */
+
+#ifndef _PRU_RPROC_H_
+#define _PRU_RPROC_H_
+
+/**
+ * struct pruss_int_map - PRU system events _to_ channel and host mapping
+ * @event: number of the system event
+ * @chnl: channel number assigned to a given @event
+ * @host: host number assigned to a given @chnl
+ *
+ * PRU system events are mapped to channels, and these channels are mapped
+ * to host interrupts. Events can be mapped to channels in a one-to-one or
+ * many-to-one ratio (multiple events per channel), and channels can be
+ * mapped to host interrupts in a one-to-one or many-to-one ratio (multiple
+ * channels per interrupt).
+ */
+struct pruss_int_map {
+	u8 event;
+	u8 chnl;
+	u8 host;
+};
+
+/**
+ * struct pru_irq_rsc - PRU firmware section header for IRQ data
+ * @type: resource type
+ * @num_evts: number of described events
+ * @pru_intc_map: PRU interrupt routing description
+ *
+ * The PRU firmware blob can contain optional .pru_irq_map ELF section, which
+ * provides the PRUSS interrupt mapping description. The pru_irq_rsc struct
+ * describes resource entry format.
+ */
+struct pru_irq_rsc {
+	u8 type;
+	u8 num_evts;
+	struct pruss_int_map pru_intc_map[];
+} __packed;
+
+#endif	/* _PRU_RPROC_H_ */