[PATCH RESEND 07/10] via-cuda: Use spinlock_irq_save/restore instead of enable/disable_irq
flat view
STALE3541d
REVIEWED: 1 (0M)
From: Finn Thain <hidden>
Date: 2017-01-01 00:57:13
Also in:
linux-m68k, lkml
Subsystem:
linux for power macintosh, the rest · Maintainer:
Linus Torvalds
Revision resend of 2 in this series; 1 review trailer.
Revisions (2)
- v1 [diff vs current]
- resend current
The cuda_start() function uses spinlock_irq_save/restore for mutual exclusion. Let's have cuda_poll() do the same when polling the VIA interrupt. The benefit to disabling local irqs when the interrupt is being polled is that the interrupt handler now has the same timing properties regardless of whether it is invoked normally or from cuda_poll(). This driver was written back when local irqs remained enabled during execution of interrupt handlers and cuda_poll() was probably trying to achieve the same effect by use of enable/disable_irq. Tested-by: Stan Johnson <redacted> Signed-off-by: Finn Thain <redacted> --- I wondered whether the use of enable/disable_irq was an attempt to reduce interrupt latency given that VIA register accesses are slow. But if the interrupt has not yet fired, only one VIA access will take place, which imposes neglible latency anyway. If the interrupt has fired, we should execute the handler under the usual context, i.e. local irqs disabled. --- drivers/macintosh/via-cuda.c | 16 +++++----------- 1 file changed, 5 insertions(+), 11 deletions(-)
diff --git a/drivers/macintosh/via-cuda.c b/drivers/macintosh/via-cuda.c
index 3212695..e3763cb 100644
--- a/drivers/macintosh/via-cuda.c
+++ b/drivers/macintosh/via-cuda.c@@ -459,14 +459,7 @@ cuda_start(void) void cuda_poll(void) { - /* cuda_interrupt only takes a normal lock, we disable - * interrupts here to avoid re-entering and thus deadlocking. - */ - if (cuda_irq) - disable_irq(cuda_irq); - cuda_interrupt(0, NULL); - if (cuda_irq) - enable_irq(cuda_irq); + cuda_interrupt(0, NULL); } EXPORT_SYMBOL(cuda_poll);
@@ -475,13 +468,14 @@ EXPORT_SYMBOL(cuda_poll); static irqreturn_t cuda_interrupt(int irq, void *arg) { + unsigned long flags; u8 status; struct adb_request *req = NULL; unsigned char ibuf[16]; int ibuf_len = 0; int complete = 0; - spin_lock(&cuda_lock); + spin_lock_irqsave(&cuda_lock, flags); /* On powermacs, this handler is registered for the VIA IRQ. But they use * just the shift register IRQ -- other VIA interrupt sources are disabled.
@@ -494,7 +488,7 @@ cuda_interrupt(int irq, void *arg) #endif { if ((in_8(&via[IFR]) & SR_INT) == 0) { - spin_unlock(&cuda_lock); + spin_unlock_irqrestore(&cuda_lock, flags); return IRQ_NONE; } else { out_8(&via[IFR], SR_INT);
@@ -616,7 +610,7 @@ cuda_interrupt(int irq, void *arg) default: pr_err("cuda_interrupt: unknown cuda_state %d?\n", cuda_state); } - spin_unlock(&cuda_lock); + spin_unlock_irqrestore(&cuda_lock, flags); if (complete && req) { void (*done)(struct adb_request *) = req->done; mb();
--
2.10.2