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media: gpio-ir-tx: spinlock is not needed to disable interrupts 

During bit-banging the IR on a gpio pin, we cannot be scheduled or have
anything interrupt us, else the generated signal will be incorrect.
Therefore, we need to disable interrupts on the local cpu. This also
disables preemption.

local_irq_disable() does exactly what we need and does not require a
spinlock.

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
This commit is contained in:
Sean Young 2020-08-13 11:08:49 +02:00 committed by Mauro Carvalho Chehab
parent a2e2d73fa2
commit 1451b93223
1 changed files with 5 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
drivers/media/rc/gpio-ir-tx.c
View File

@ -19,8 +19,6 @@ struct gpio_ir {
struct gpio_desc *gpio;
unsigned int carrier;
unsigned int duty_cycle;
/* we need a spinlock to hold the cpu while transmitting */
spinlock_t lock;
};
static const struct of_device_id gpio_ir_tx_of_match[] = {
@ -53,12 +51,11 @@ static int gpio_ir_tx_set_carrier(struct rc_dev *dev, u32 carrier)
static void gpio_ir_tx_unmodulated(struct gpio_ir *gpio_ir, uint *txbuf,
uint count)
{
unsigned long flags;
ktime_t edge;
s32 delta;
int i;
spin_lock_irqsave(&gpio_ir->lock, flags);
local_irq_disable();
edge = ktime_get();
@ -72,14 +69,11 @@ static void gpio_ir_tx_unmodulated(struct gpio_ir *gpio_ir, uint *txbuf,
}
gpiod_set_value(gpio_ir->gpio, 0);
spin_unlock_irqrestore(&gpio_ir->lock, flags);
}
static void gpio_ir_tx_modulated(struct gpio_ir *gpio_ir, uint *txbuf,
uint count)
{
unsigned long flags;
ktime_t edge;
/*
* delta should never exceed 0.5 seconds (IR_MAX_DURATION) and on
@ -95,7 +89,7 @@ static void gpio_ir_tx_modulated(struct gpio_ir *gpio_ir, uint *txbuf,
space = DIV_ROUND_CLOSEST((100 - gpio_ir->duty_cycle) *
(NSEC_PER_SEC / 100), gpio_ir->carrier);
spin_lock_irqsave(&gpio_ir->lock, flags);
local_irq_disable();
edge = ktime_get();
@ -128,19 +122,20 @@ static void gpio_ir_tx_modulated(struct gpio_ir *gpio_ir, uint *txbuf,
edge = last;
}
}
spin_unlock_irqrestore(&gpio_ir->lock, flags);
}
static int gpio_ir_tx(struct rc_dev *dev, unsigned int *txbuf,
unsigned int count)
{
struct gpio_ir *gpio_ir = dev->priv;
unsigned long flags;
local_irq_save(flags);
if (gpio_ir->carrier)
gpio_ir_tx_modulated(gpio_ir, txbuf, count);
else
gpio_ir_tx_unmodulated(gpio_ir, txbuf, count);
local_irq_restore(flags);
return count;
}
@ -176,7 +171,6 @@ static int gpio_ir_tx_probe(struct platform_device *pdev)
gpio_ir->carrier = 38000;
gpio_ir->duty_cycle = 50;
spin_lock_init(&gpio_ir->lock);
rc = devm_rc_register_device(&pdev->dev, rcdev);
if (rc < 0)