drivers/irqchip/irq-sifive-plic.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2017 SiFive
   4  * Copyright (C) 2018 Christoph Hellwig
   5  */
   6 #define pr_fmt(fmt) "plic: " fmt
   7 #include <linux/interrupt.h>
   8 #include <linux/io.h>
   9 #include <linux/irq.h>
  10 #include <linux/irqchip.h>
  11 #include <linux/irqdomain.h>
  12 #include <linux/module.h>
  13 #include <linux/of.h>
  14 #include <linux/of_address.h>
  15 #include <linux/of_irq.h>
  16 #include <linux/platform_device.h>
  17 #include <linux/spinlock.h>
  18 #include <asm/smp.h>
  19
  20 /*
  21  * This driver implements a version of the RISC-V PLIC with the actual layout
  22  * specified in chapter 8 of the SiFive U5 Coreplex Series Manual:
  23  *
  24  *     https://static.dev.sifive.com/U54-MC-RVCoreIP.pdf
  25  *
  26  * The largest number supported by devices marked as 'sifive,plic-1.0.0', is
  27  * 1024, of which device 0 is defined as non-existent by the RISC-V Privileged
  28  * Spec.
  29  */
  30
  31 #define MAX_DEVICES                     1024
  32 #define MAX_CONTEXTS                    15872
  33
  34 /*
  35  * Each interrupt source has a priority register associated with it.
  36  * We always hardwire it to one in Linux.
  37  */
  38 #define PRIORITY_BASE                   0
  39 #define     PRIORITY_PER_ID             4
  40
  41 /*
  42  * Each hart context has a vector of interrupt enable bits associated with it.
  43  * There's one bit for each interrupt source.
  44  */
  45 #define ENABLE_BASE                     0x2000
  46 #define     ENABLE_PER_HART             0x80
  47
  48 /*
  49  * Each hart context has a set of control registers associated with it.  Right
  50  * now there's only two: a source priority threshold over which the hart will
  51  * take an interrupt, and a register to claim interrupts.
  52  */
  53 #define CONTEXT_BASE                    0x200000
  54 #define     CONTEXT_PER_HART            0x1000
  55 #define     CONTEXT_THRESHOLD           0x00
  56 #define     CONTEXT_CLAIM               0x04
  57
  58 static void __iomem *plic_regs;
  59
  60 struct plic_handler {
  61         bool                    present;
  62         void __iomem            *hart_base;
  63         /*
  64          * Protect mask operations on the registers given that we can't
  65          * assume atomic memory operations work on them.
  66          */
  67         raw_spinlock_t          enable_lock;
  68         void __iomem            *enable_base;
  69 };
  70 static DEFINE_PER_CPU(struct plic_handler, plic_handlers);
  71
  72 static inline void plic_toggle(struct plic_handler *handler,
  73                                 int hwirq, int enable)
  74 {
  75         u32 __iomem *reg = handler->enable_base + (hwirq / 32) * sizeof(u32);
  76         u32 hwirq_mask = 1 << (hwirq % 32);
  77
  78         raw_spin_lock(&handler->enable_lock);
  79         if (enable)
  80                 writel(readl(reg) | hwirq_mask, reg);
  81         else
  82                 writel(readl(reg) & ~hwirq_mask, reg);
  83         raw_spin_unlock(&handler->enable_lock);
  84 }
  85
  86 static inline void plic_irq_toggle(const struct cpumask *mask,
  87                                    int hwirq, int enable)
  88 {
  89         int cpu;
  90
  91         writel(enable, plic_regs + PRIORITY_BASE + hwirq * PRIORITY_PER_ID);
  92         for_each_cpu(cpu, mask) {
  93                 struct plic_handler *handler = per_cpu_ptr(&plic_handlers, cpu);
  94
  95                 if (handler->present)
  96                         plic_toggle(handler, hwirq, enable);
  97         }
  98 }
  99
 100 static void plic_irq_unmask(struct irq_data *d)
 101 {
 102         unsigned int cpu = cpumask_any_and(irq_data_get_affinity_mask(d),
 103                                            cpu_online_mask);
 104         if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
 105                 return;
 106         plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1);
 107 }
 108
 109 static void plic_irq_mask(struct irq_data *d)
 110 {
 111         plic_irq_toggle(cpu_possible_mask, d->hwirq, 0);
 112 }
 113
 114 #ifdef CONFIG_SMP
 115 static int plic_set_affinity(struct irq_data *d,
 116                              const struct cpumask *mask_val, bool force)
 117 {
 118         unsigned int cpu;
 119
 120         if (force)
 121                 cpu = cpumask_first(mask_val);
 122         else
 123                 cpu = cpumask_any_and(mask_val, cpu_online_mask);
 124
 125         if (cpu >= nr_cpu_ids)
 126                 return -EINVAL;
 127
 128         plic_irq_toggle(cpu_possible_mask, d->hwirq, 0);
 129         plic_irq_toggle(cpumask_of(cpu), d->hwirq, 1);
 130
 131         irq_data_update_effective_affinity(d, cpumask_of(cpu));
 132
 133         return IRQ_SET_MASK_OK_DONE;
 134 }
 135 #endif
 136
 137 static void plic_irq_eoi(struct irq_data *d)
 138 {
 139         struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
 140
 141         writel(d->hwirq, handler->hart_base + CONTEXT_CLAIM);
 142 }
 143
 144 static struct irq_chip plic_chip = {
 145         .name           = "SiFive PLIC",
 146         .irq_mask       = plic_irq_mask,
 147         .irq_unmask     = plic_irq_unmask,
 148         .irq_eoi        = plic_irq_eoi,
 149 #ifdef CONFIG_SMP
 150         .irq_set_affinity = plic_set_affinity,
 151 #endif
 152 };
 153
 154 static int plic_irqdomain_map(struct irq_domain *d, unsigned int irq,
 155                               irq_hw_number_t hwirq)
 156 {
 157         irq_set_chip_and_handler(irq, &plic_chip, handle_fasteoi_irq);
 158         irq_set_chip_data(irq, NULL);
 159         irq_set_noprobe(irq);
 160         return 0;
 161 }
 162
 163 static const struct irq_domain_ops plic_irqdomain_ops = {
 164         .map            = plic_irqdomain_map,
 165         .xlate          = irq_domain_xlate_onecell,
 166 };
 167
 168 static struct irq_domain *plic_irqdomain;
 169
 170 /*
 171  * Handling an interrupt is a two-step process: first you claim the interrupt
 172  * by reading the claim register, then you complete the interrupt by writing
 173  * that source ID back to the same claim register.  This automatically enables
 174  * and disables the interrupt, so there's nothing else to do.
 175  */
 176 static void plic_handle_irq(struct pt_regs *regs)
 177 {
 178         struct plic_handler *handler = this_cpu_ptr(&plic_handlers);
 179         void __iomem *claim = handler->hart_base + CONTEXT_CLAIM;
 180         irq_hw_number_t hwirq;
 181
 182         WARN_ON_ONCE(!handler->present);
 183
 184         csr_clear(CSR_IE, IE_EIE);
 185         while ((hwirq = readl(claim))) {
 186                 int irq = irq_find_mapping(plic_irqdomain, hwirq);
 187
 188                 if (unlikely(irq <= 0))
 189                         pr_warn_ratelimited("can't find mapping for hwirq %lu\n",
 190                                         hwirq);
 191                 else
 192                         generic_handle_irq(irq);
 193         }
 194         csr_set(CSR_IE, IE_EIE);
 195 }
 196
 197 /*
 198  * Walk up the DT tree until we find an active RISC-V core (HART) node and
 199  * extract the cpuid from it.
 200  */
 201 static int plic_find_hart_id(struct device_node *node)
 202 {
 203         for (; node; node = node->parent) {
 204                 if (of_device_is_compatible(node, "riscv"))
 205                         return riscv_of_processor_hartid(node);
 206         }
 207
 208         return -1;
 209 }
 210
 211 static int __init plic_init(struct device_node *node,
 212                 struct device_node *parent)
 213 {
 214         int error = 0, nr_contexts, nr_handlers = 0, i;
 215         u32 nr_irqs;
 216
 217         if (plic_regs) {
 218                 pr_warn("PLIC already present.\n");
 219                 return -ENXIO;
 220         }
 221
 222         plic_regs = of_iomap(node, 0);
 223         if (WARN_ON(!plic_regs))
 224                 return -EIO;
 225
 226         error = -EINVAL;
 227         of_property_read_u32(node, "riscv,ndev", &nr_irqs);
 228         if (WARN_ON(!nr_irqs))
 229                 goto out_iounmap;
 230
 231         nr_contexts = of_irq_count(node);
 232         if (WARN_ON(!nr_contexts))
 233                 goto out_iounmap;
 234         if (WARN_ON(nr_contexts < num_possible_cpus()))
 235                 goto out_iounmap;
 236
 237         error = -ENOMEM;
 238         plic_irqdomain = irq_domain_add_linear(node, nr_irqs + 1,
 239                         &plic_irqdomain_ops, NULL);
 240         if (WARN_ON(!plic_irqdomain))
 241                 goto out_iounmap;
 242
 243         for (i = 0; i < nr_contexts; i++) {
 244                 struct of_phandle_args parent;
 245                 struct plic_handler *handler;
 246                 irq_hw_number_t hwirq;
 247                 int cpu, hartid;
 248                 u32 threshold = 0;
 249
 250                 if (of_irq_parse_one(node, i, &parent)) {
 251                         pr_err("failed to parse parent for context %d.\n", i);
 252                         continue;
 253                 }
 254
 255                 /*
 256                  * Skip contexts other than external interrupts for our
 257                  * privilege level.
 258                  */
 259                 if (parent.args[0] != IRQ_EXT)
 260                         continue;
 261
 262                 hartid = plic_find_hart_id(parent.np);
 263                 if (hartid < 0) {
 264                         pr_warn("failed to parse hart ID for context %d.\n", i);
 265                         continue;
 266                 }
 267
 268                 cpu = riscv_hartid_to_cpuid(hartid);
 269                 if (cpu < 0) {
 270                         pr_warn("Invalid cpuid for context %d\n", i);
 271                         continue;
 272                 }
 273
 274                 /*
 275                  * When running in M-mode we need to ignore the S-mode handler.
 276                  * Here we assume it always comes later, but that might be a
 277                  * little fragile.
 278                  */
 279                 handler = per_cpu_ptr(&plic_handlers, cpu);
 280                 if (handler->present) {
 281                         pr_warn("handler already present for context %d.\n", i);
 282                         threshold = 0xffffffff;
 283                         goto done;
 284                 }
 285
 286                 handler->present = true;
 287                 handler->hart_base =
 288                         plic_regs + CONTEXT_BASE + i * CONTEXT_PER_HART;
 289                 raw_spin_lock_init(&handler->enable_lock);
 290                 handler->enable_base =
 291                         plic_regs + ENABLE_BASE + i * ENABLE_PER_HART;
 292
 293 done:
 294                 /* priority must be > threshold to trigger an interrupt */
 295                 writel(threshold, handler->hart_base + CONTEXT_THRESHOLD);
 296                 for (hwirq = 1; hwirq <= nr_irqs; hwirq++)
 297                         plic_toggle(handler, hwirq, 0);
 298                 nr_handlers++;
 299         }
 300
 301         pr_info("mapped %d interrupts with %d handlers for %d contexts.\n",
 302                 nr_irqs, nr_handlers, nr_contexts);
 303         set_handle_irq(plic_handle_irq);
 304         return 0;
 305
 306 out_iounmap:
 307         iounmap(plic_regs);
 308         return error;
 309 }
 310
 311 IRQCHIP_DECLARE(sifive_plic, "sifive,plic-1.0.0", plic_init);
 312 IRQCHIP_DECLARE(riscv_plic0, "riscv,plic0", plic_init); /* for legacy systems */