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/*
* Open Multi-Processor Interrupt Controller driver
*
* Copyright (C) 2014 Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>
* Copyright (C) 2017 Stafford Horne <shorne@gmail.com>
*
* This file is licensed under the terms of the GNU General Public License
* version 2. This program is licensed "as is" without any warranty of any
* kind, whether express or implied.
*
* The ompic device handles IPI communication between cores in multi-core
* OpenRISC systems.
*
* Registers
*
* For each CPU the ompic has 2 registers. The control register for sending
* and acking IPIs and the status register for receiving IPIs. The register
* layouts are as follows:
*
* Control register
* +---------+---------+----------+---------+
* | 31 | 30 | 29 .. 16 | 15 .. 0 |
* ----------+---------+----------+----------
* | IRQ ACK | IRQ GEN | DST CORE | DATA |
* +---------+---------+----------+---------+
*
* Status register
* +----------+-------------+----------+---------+
* | 31 | 30 | 29 .. 16 | 15 .. 0 |
* -----------+-------------+----------+---------+
* | Reserved | IRQ Pending | SRC CORE | DATA |
* +----------+-------------+----------+---------+
*
* Architecture
*
* - The ompic generates a level interrupt to the CPU PIC when a message is
* ready. Messages are delivered via the memory bus.
* - The ompic does not have any interrupt input lines.
* - The ompic is wired to the same irq line on each core.
* - Devices are wired to the same irq line on each core.
*
* +---------+ +---------+
* | CPU | | CPU |
* | Core 0 |<==\ (memory access) /==>| Core 1 |
* | [ PIC ]| | | | [ PIC ]|
* +----^-^--+ | | +----^-^--+
* | | v v | |
* <====|=|=================================|=|==> (memory bus)
* | | ^ ^ | |
* (ipi | +------|---------+--------|-------|-+ (device irq)
* irq | | | | |
* core0)| +------|---------|--------|-------+ (ipi irq core1)
* | | | | |
* +----o-o-+ | +--------+ |
* | ompic |<===/ | Device |<===/
* | IPI | +--------+
* +--------+*
*
*/
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/smp.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/of_address.h>
#include <linux/irqchip.h>
#define OMPIC_CPUBYTES 8
#define OMPIC_CTRL(cpu) (0x0 + (cpu * OMPIC_CPUBYTES))
#define OMPIC_STAT(cpu) (0x4 + (cpu * OMPIC_CPUBYTES))
#define OMPIC_CTRL_IRQ_ACK (1 << 31)
#define OMPIC_CTRL_IRQ_GEN (1 << 30)
#define OMPIC_CTRL_DST(cpu) (((cpu) & 0x3fff) << 16)
#define OMPIC_STAT_IRQ_PENDING (1 << 30)
#define OMPIC_DATA(x) ((x) & 0xffff)
DEFINE_PER_CPU(unsigned long, ops);
static void __iomem *ompic_base;
static inline u32 ompic_readreg(void __iomem *base, loff_t offset)
{
return ioread32be(base + offset);
}
static void ompic_writereg(void __iomem *base, loff_t offset, u32 data)
{
iowrite32be(data, base + offset);
}
static void ompic_raise_softirq(const struct cpumask *mask,
unsigned int ipi_msg)
{
unsigned int dst_cpu;
unsigned int src_cpu = smp_processor_id();
for_each_cpu(dst_cpu, mask) {
set_bit(ipi_msg, &per_cpu(ops, dst_cpu));
/*
* On OpenRISC the atomic set_bit() call implies a memory
* barrier. Otherwise we would need: smp_wmb(); paired
* with the read in ompic_ipi_handler.
*/
ompic_writereg(ompic_base, OMPIC_CTRL(src_cpu),
OMPIC_CTRL_IRQ_GEN |
OMPIC_CTRL_DST(dst_cpu) |
OMPIC_DATA(1));
}
}
static irqreturn_t ompic_ipi_handler(int irq, void *dev_id)
{
unsigned int cpu = smp_processor_id();
unsigned long *pending_ops = &per_cpu(ops, cpu);
unsigned long ops;
ompic_writereg(ompic_base, OMPIC_CTRL(cpu), OMPIC_CTRL_IRQ_ACK);
while ((ops = xchg(pending_ops, 0)) != 0) {
/*
* On OpenRISC the atomic xchg() call implies a memory
* barrier. Otherwise we may need an smp_rmb(); paired
* with the write in ompic_raise_softirq.
*/
do {
unsigned long ipi_msg;
ipi_msg = __ffs(ops);
ops &= ~(1UL << ipi_msg);
handle_IPI(ipi_msg);
} while (ops);
}
return IRQ_HANDLED;
}
static int __init ompic_of_init(struct device_node *node,
struct device_node *parent)
{
struct resource res;
int irq;
int ret;
/* Validate the DT */
if (ompic_base) {
pr_err("ompic: duplicate ompic's are not supported");
return -EEXIST;
}
if (of_address_to_resource(node, 0, &res)) {
pr_err("ompic: reg property requires an address and size");
return -EINVAL;
}
if (resource_size(&res) < (num_possible_cpus() * OMPIC_CPUBYTES)) {
pr_err("ompic: reg size, currently %d must be at least %d",
resource_size(&res),
(num_possible_cpus() * OMPIC_CPUBYTES));
return -EINVAL;
}
/* Setup the device */
ompic_base = ioremap(res.start, resource_size(&res));
if (!ompic_base) {
pr_err("ompic: unable to map registers");
return -ENOMEM;
}
irq = irq_of_parse_and_map(node, 0);
if (irq <= 0) {
pr_err("ompic: unable to parse device irq");
ret = -EINVAL;
goto out_unmap;
}
ret = request_irq(irq, ompic_ipi_handler, IRQF_PERCPU,
"ompic_ipi", NULL);
if (ret)
goto out_irq_disp;
set_smp_cross_call(ompic_raise_softirq);
return 0;
out_irq_disp:
irq_dispose_mapping(irq);
out_unmap:
iounmap(ompic_base);
ompic_base = NULL;
return ret;
}
IRQCHIP_DECLARE(ompic, "openrisc,ompic", ompic_of_init);
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