Re: [PATCH] leds-bcm6328: Reuse bcm6328_led_set() instead of copying its functionality
From: Jacek Anaszewski
Date: Thu Nov 05 2015 - 05:41:13 EST
Hi Alvaro,
On 11/04/2015 04:46 PM, Ãlvaro FernÃndez Rojas wrote:
Hello Jacek,
BCM6328_LED_MODE_ON and BCM6328_LED_MODE_OFF values were extracted from
Broadcom's GPL code, in which they assume leds are active low by default.
I can confirm the code is correct as it is right now, since those values
match the active high / low values of the LEDs managed by GPIO instead
of by using this driver.
BCM6328_LED_MODE_ON and BCM6328_LED_MODE_OFF should represent the values
that actually set the LED state according to the current logic.
Otherwise it will confuse people who will be analyzing this code.
We are interested in the logic as it is seen from this driver's
perspective and not GPIO perspective.
IMO the values should be swapped.
Best Regards,
Jacek Anaszewski
El 04/11/2015 a las 16:41, Jacek Anaszewski escribiÃ:
Hi Simon,
Thanks for the patch. Generally this patch touches two
areas - replacement of redundant code with bcm6328_led_set,
and locking reorganization. These should be split into
two separate patches. Nonetheless, I've noticed some
issues in the code, please refer below.
On 10/29/2015 08:48 PM, Simon Arlott wrote:
When ensuring a consistent initial LED state in bcm6328_led (as they may
be blinking instead of on/off), the LED register is set using a copy of
bcm6328_led_set(). To avoid further errors relating to active low
handling,
call this function directly instead.
As bcm6328_led_set() expects to acquire the spinlock, narrow the locking
to only cover reading of the current state. There is no need to hold the
spinlock between reading the current value and setting it again because
the LED device has not yet been registered.
Signed-off-by: Simon Arlott <simon@xxxxxxxxxxx>
---
drivers/leds/leds-bcm6328.c | 14 +++++---------
1 file changed, 5 insertions(+), 9 deletions(-)
diff --git a/drivers/leds/leds-bcm6328.c b/drivers/leds/leds-bcm6328.c
index c7ea5c6..db327bd 100644
--- a/drivers/leds/leds-bcm6328.c
+++ b/drivers/leds/leds-bcm6328.c
@@ -264,7 +264,6 @@ static int bcm6328_led(struct device *dev, struct
device_node *nc, u32 reg,
unsigned long *blink_leds, unsigned long *blink_delay)
{
struct bcm6328_led *led;
- unsigned long flags;
const char *state;
int rc;
@@ -286,13 +285,12 @@ static int bcm6328_led(struct device *dev,
struct device_node *nc, u32 reg,
"linux,default-trigger",
NULL);
- spin_lock_irqsave(lock, flags);
if (!of_property_read_string(nc, "default-state", &state)) {
if (!strcmp(state, "on")) {
led->cdev.brightness = LED_FULL;
} else if (!strcmp(state, "keep")) {
void __iomem *mode;
- unsigned long val, shift;
+ unsigned long val, shift, flags;
shift = bcm6328_pin2shift(led->pin);
if (shift / 16)
@@ -300,9 +298,12 @@ static int bcm6328_led(struct device *dev,
struct device_node *nc, u32 reg,
else
mode = mem + BCM6328_REG_MODE_LO;
+ spin_lock_irqsave(lock, flags);
val = bcm6328_led_read(mode) >>
BCM6328_LED_SHIFT(shift % 16);
val &= BCM6328_LED_MODE_MASK;
+ spin_unlock_irqrestore(lock, flags);
+
if ((led->active_low && val == BCM6328_LED_MODE_ON) ||
(!led->active_low && val == BCM6328_LED_MODE_OFF))
led->cdev.brightness = LED_FULL;
@@ -315,12 +316,7 @@ static int bcm6328_led(struct device *dev,
struct device_node *nc, u32 reg,
led->cdev.brightness = LED_OFF;
}
- if ((led->active_low && led->cdev.brightness == LED_FULL) ||
- (!led->active_low && led->cdev.brightness == LED_OFF))
- bcm6328_led_mode(led, BCM6328_LED_MODE_ON);
- else
- bcm6328_led_mode(led, BCM6328_LED_MODE_OFF);
There are some problems with active_low mode here, I didn't recognize
earlier.
I'd expect that active_low implies reverse logic, i.e.:
LED_FULL -> bcm6328_led_mode(led, BCM6328_LED_MODE_OFF);
LED_OFF -> bcm6328_led_mode(led, BCM6328_LED_MODE_ON);
Let's take a look at bcm6328_led_set:
if ((led->active_low && value == LED_OFF) ||
(!led->active_low && value != LED_OFF))
bcm6328_led_mode(led, BCM6328_LED_MODE_OFF);
else
bcm6328_led_mode(led, BCM6328_LED_MODE_ON);
which, for active_low case, boils down to:
LED_FULL -> bcm6328_led_mode(led, BCM6328_LED_MODE_ON);
LED_OFF -> bcm6328_led_mode(led, BCM6328_LED_MODE_OFF);
and for !active_low case to:
LED_FULL -> bcm6328_led_mode(led, BCM6328_LED_MODE_OFF);
LED_OFF -> bcm6328_led_mode(led, BCM6328_LED_MODE_ON);
so, this is the other way round.
In bcm6328_led we have:
if ((led->active_low && val == BCM6328_LED_MODE_ON) ||
(!led->active_low && val == BCM6328_LED_MODE_OFF))
led->cdev.brightness = LED_FULL;
else
led->cdev.brightness = LED_OFF;
which, for active_low case, boils down to:
BCM6328_LED_MODE_ON -> led->cdev.brightness = LED_FULL
BCM6328_LED_MODE_OFF -> led->cdev.brightness = LED_OFF
and for !active_low case to:
BCM6328_LED_MODE_ON -> led->cdev.brightness = LED_OFF
BCM6328_LED_MODE_OFF -> led->cdev.brightness = LED_FULL
again, the other way round.
All this looks like active_low really means active high.
Correct me if I'm wrong.
Alvaro, Jonas, could you also help to clarify this discrepancy?
- spin_unlock_irqrestore(lock, flags);
+ bcm6328_led_set(&led->cdev, led->cdev.brightness);
led->cdev.brightness_set = bcm6328_led_set;
led->cdev.blink_set = bcm6328_blink_set;
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