Merge branch 'spi-5.1' into spi-linus
[platform/kernel/linux-rpi.git] / lib / irq_poll.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Functions related to interrupt-poll handling in the block layer. This
4  * is similar to NAPI for network devices.
5  */
6 #include <linux/kernel.h>
7 #include <linux/module.h>
8 #include <linux/init.h>
9 #include <linux/bio.h>
10 #include <linux/interrupt.h>
11 #include <linux/cpu.h>
12 #include <linux/irq_poll.h>
13 #include <linux/delay.h>
14
15 static unsigned int irq_poll_budget __read_mostly = 256;
16
17 static DEFINE_PER_CPU(struct list_head, blk_cpu_iopoll);
18
19 /**
20  * irq_poll_sched - Schedule a run of the iopoll handler
21  * @iop:      The parent iopoll structure
22  *
23  * Description:
24  *     Add this irq_poll structure to the pending poll list and trigger the
25  *     raise of the blk iopoll softirq.
26  **/
27 void irq_poll_sched(struct irq_poll *iop)
28 {
29         unsigned long flags;
30
31         if (test_bit(IRQ_POLL_F_DISABLE, &iop->state))
32                 return;
33         if (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))
34                 return;
35
36         local_irq_save(flags);
37         list_add_tail(&iop->list, this_cpu_ptr(&blk_cpu_iopoll));
38         raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
39         local_irq_restore(flags);
40 }
41 EXPORT_SYMBOL(irq_poll_sched);
42
43 /**
44  * __irq_poll_complete - Mark this @iop as un-polled again
45  * @iop:      The parent iopoll structure
46  *
47  * Description:
48  *     See irq_poll_complete(). This function must be called with interrupts
49  *     disabled.
50  **/
51 static void __irq_poll_complete(struct irq_poll *iop)
52 {
53         list_del(&iop->list);
54         smp_mb__before_atomic();
55         clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);
56 }
57
58 /**
59  * irq_poll_complete - Mark this @iop as un-polled again
60  * @iop:      The parent iopoll structure
61  *
62  * Description:
63  *     If a driver consumes less than the assigned budget in its run of the
64  *     iopoll handler, it'll end the polled mode by calling this function. The
65  *     iopoll handler will not be invoked again before irq_poll_sched()
66  *     is called.
67  **/
68 void irq_poll_complete(struct irq_poll *iop)
69 {
70         unsigned long flags;
71
72         local_irq_save(flags);
73         __irq_poll_complete(iop);
74         local_irq_restore(flags);
75 }
76 EXPORT_SYMBOL(irq_poll_complete);
77
78 static void __latent_entropy irq_poll_softirq(struct softirq_action *h)
79 {
80         struct list_head *list = this_cpu_ptr(&blk_cpu_iopoll);
81         int rearm = 0, budget = irq_poll_budget;
82         unsigned long start_time = jiffies;
83
84         local_irq_disable();
85
86         while (!list_empty(list)) {
87                 struct irq_poll *iop;
88                 int work, weight;
89
90                 /*
91                  * If softirq window is exhausted then punt.
92                  */
93                 if (budget <= 0 || time_after(jiffies, start_time)) {
94                         rearm = 1;
95                         break;
96                 }
97
98                 local_irq_enable();
99
100                 /* Even though interrupts have been re-enabled, this
101                  * access is safe because interrupts can only add new
102                  * entries to the tail of this list, and only ->poll()
103                  * calls can remove this head entry from the list.
104                  */
105                 iop = list_entry(list->next, struct irq_poll, list);
106
107                 weight = iop->weight;
108                 work = 0;
109                 if (test_bit(IRQ_POLL_F_SCHED, &iop->state))
110                         work = iop->poll(iop, weight);
111
112                 budget -= work;
113
114                 local_irq_disable();
115
116                 /*
117                  * Drivers must not modify the iopoll state, if they
118                  * consume their assigned weight (or more, some drivers can't
119                  * easily just stop processing, they have to complete an
120                  * entire mask of commands).In such cases this code
121                  * still "owns" the iopoll instance and therefore can
122                  * move the instance around on the list at-will.
123                  */
124                 if (work >= weight) {
125                         if (test_bit(IRQ_POLL_F_DISABLE, &iop->state))
126                                 __irq_poll_complete(iop);
127                         else
128                                 list_move_tail(&iop->list, list);
129                 }
130         }
131
132         if (rearm)
133                 __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
134
135         local_irq_enable();
136 }
137
138 /**
139  * irq_poll_disable - Disable iopoll on this @iop
140  * @iop:      The parent iopoll structure
141  *
142  * Description:
143  *     Disable io polling and wait for any pending callbacks to have completed.
144  **/
145 void irq_poll_disable(struct irq_poll *iop)
146 {
147         set_bit(IRQ_POLL_F_DISABLE, &iop->state);
148         while (test_and_set_bit(IRQ_POLL_F_SCHED, &iop->state))
149                 msleep(1);
150         clear_bit(IRQ_POLL_F_DISABLE, &iop->state);
151 }
152 EXPORT_SYMBOL(irq_poll_disable);
153
154 /**
155  * irq_poll_enable - Enable iopoll on this @iop
156  * @iop:      The parent iopoll structure
157  *
158  * Description:
159  *     Enable iopoll on this @iop. Note that the handler run will not be
160  *     scheduled, it will only mark it as active.
161  **/
162 void irq_poll_enable(struct irq_poll *iop)
163 {
164         BUG_ON(!test_bit(IRQ_POLL_F_SCHED, &iop->state));
165         smp_mb__before_atomic();
166         clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);
167 }
168 EXPORT_SYMBOL(irq_poll_enable);
169
170 /**
171  * irq_poll_init - Initialize this @iop
172  * @iop:      The parent iopoll structure
173  * @weight:   The default weight (or command completion budget)
174  * @poll_fn:  The handler to invoke
175  *
176  * Description:
177  *     Initialize and enable this irq_poll structure.
178  **/
179 void irq_poll_init(struct irq_poll *iop, int weight, irq_poll_fn *poll_fn)
180 {
181         memset(iop, 0, sizeof(*iop));
182         INIT_LIST_HEAD(&iop->list);
183         iop->weight = weight;
184         iop->poll = poll_fn;
185 }
186 EXPORT_SYMBOL(irq_poll_init);
187
188 static int irq_poll_cpu_dead(unsigned int cpu)
189 {
190         /*
191          * If a CPU goes away, splice its entries to the current CPU
192          * and trigger a run of the softirq
193          */
194         local_irq_disable();
195         list_splice_init(&per_cpu(blk_cpu_iopoll, cpu),
196                          this_cpu_ptr(&blk_cpu_iopoll));
197         __raise_softirq_irqoff(IRQ_POLL_SOFTIRQ);
198         local_irq_enable();
199
200         return 0;
201 }
202
203 static __init int irq_poll_setup(void)
204 {
205         int i;
206
207         for_each_possible_cpu(i)
208                 INIT_LIST_HEAD(&per_cpu(blk_cpu_iopoll, i));
209
210         open_softirq(IRQ_POLL_SOFTIRQ, irq_poll_softirq);
211         cpuhp_setup_state_nocalls(CPUHP_IRQ_POLL_DEAD, "irq_poll:dead", NULL,
212                                   irq_poll_cpu_dead);
213         return 0;
214 }
215 subsys_initcall(irq_poll_setup);