Skip to contentSkip to conversation

ARM: pxa: hx4700: Fix backlight PWM device number

PATCH New Paul Parsons 2 participants 5 messages Sep 26, 2012 2 messages not in the archive

Subsystems (3)
Arm (32-bit) Arm sub-architectures PXA2xx/PXA3xx support
lore
Share & tools
lore

Paul Parsons

author
#1 lore raw

PATCH 1/1 ARM: pxa: hx4700: Fix backlight PWM device number

In reply to a message not in the archive

Recent changes to PXA PWM support changed the PXA27X PWM device numbering scheme.

The linux-3.5 PXA PWM driver followed the hardware numbering scheme for the 4 PWMs, while the linux-3.6-rc1 PXA PWM driver has adopted a linear numbering scheme:

Address Hardware 3.5 pwm_id 3.6-rc1 pwm_id
0x40b00000 PWM0 0 0
0x40b00010 PWM2 2 1
0x40c00000 PWM1 1 2
0x40c00010 PWM3 3 3

The hx4700 backlight uses PWM1 at 0x40c00000. Consequently the pwm_id must be changed from 1 to 2.

Signed-off-by Paul Parsons <[email protected]>
Cc Thierry Reding <[email protected]>
---
  arch/arm/mach-pxa/hx4700.c |    2 +-
  1 files changed, 1 insertions(+), 1 deletions(-)
arch/arm/mach-pxa/hx4700.c +1 -1
index e631198..3720f99 100644
@@ -556,7 +556,7 @@ static struct platform_device hx4700_lcd = {
   */
 
  static struct platform_pwm_backlight_data backlight_data = {
-	.pwm_id         = 1,
+	.pwm_id         = 2,	/* PWM1 */
  	.max_brightness = 200,
  	.dft_brightness = 100,
  	.pwm_period_ns  = 30923,
Signature · 1 line
1.7.8.6
#2 lore raw

PATCH 1/1 ARM: pxa: hx4700: Fix backlight PWM device number

Quoted 7 lines · Paul Parsons

Recent changes to PXA PWM support changed the PXA27X PWM device numbering scheme.

The linux-3.5 PXA PWM driver followed the hardware numbering scheme for the 4 PWMs, while the linux-3.6-rc1 PXA PWM driver has adopted a linear numbering scheme:

Quoted 5 lines
Address         Hardware        3.5 pwm_id      3.6-rc1 pwm_id
0x40b00000      PWM0            0               0
0x40b00010      PWM2            2               1
0x40c00000      PWM1            1               2
0x40c00010      PWM3            3               3

Looks very weird to me. Maybe it would be better to fix pwm numbering scheme to prevent breakage of
other machines?

Regards
Vasily

Quoted 30 lines

The hx4700 backlight uses PWM1 at 0x40c00000. Consequently the pwm_id must be changed from 1 to 2.

Signed-off-by Paul Parsons <[email protected]>
Cc Thierry Reding <[email protected]>
---
 arch/arm/mach-pxa/hx4700.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
arch/arm/mach-pxa/hx4700.c +1 -2
index e631198..3720f99 100644
@@ -556,7 +556,7 @@ static struct platform_device hx4700_lcd = {
  */
 
 static struct platform_pwm_backlight_data backlight_data = {
-       .pwm_id         = 1,
+       .pwm_id         = 2,    /* PWM1 */
        .max_brightness = 200,
        .dft_brightness = 100,
        .pwm_period_ns  = 30923,
--

1.7.8.6

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel at lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

author
#3 lore raw

PATCH 1/1 ARM: pxa: hx4700: Fix backlight PWM device number

Hello Vasily,

Quoted 14 lines · Vasily Khoruzhick
Quoted 7 lines · Paul Parsons

Recent changes to PXA PWM support changed the PXA27X PWM device numbering scheme.

The linux-3.5 PXA PWM driver followed the hardware numbering scheme for the 4 PWMs, while the linux-3.6-rc1 PXA PWM driver has adopted a linear numbering scheme:

Quoted 5 lines
Address         Hardware        3.5 pwm_id      3.6-rc1 pwm_id
0x40b00000      PWM0            0               0
0x40b00010      PWM2            2               1
0x40c00000      PWM1            1               2
0x40c00010      PWM3            3               3
Quoted 3 lines

Looks very weird to me. Maybe it would be better to fix pwm numbering scheme to prevent breakage of
other machines?

I thought the same thing. However the code doesn't make it easy:

1. The definition of pwm_id values moved from the pwm_probe() in arch/arm/plat-pxa/pwm.c to pwmchip_add() in drivers/pwm/core.c. Changing the latter generic code would impact all of the PWM drivers, not just the PXA PWM driver.

2. Changing just the PXA PWM driver would require its pwm_ops handlers (config(), enable(), disable()) to quietly translate between PWM1 and PWM2 devices. However PWM1 and PWM2 are on different chips (i.e. pwm_chip structures). So what would the driver do when there is only one chip? i.e.:
a) Between the first and second calls to pwm_probe().
b) Between the first and second calls to pwm_remove().
And in any case quietly translating between PWM1 and PWM2 just doesn't seem like a good idea: sooner or later it will quietly break the generic code.

On balance it seemed preferable to change the platform code.

Regards,
Paul

author
#5 lore raw

PATCH 1/1 ARM: pxa: hx4700: Fix backlight PWM device number

In reply to a message not in the archive

Hello Thierry,

Quoted 33 lines · Thierry Reding
Quoted 13 lines · Paul Parsons

Recent changes to PXA PWM support changed the PXA27X PWM device numbering scheme.

The linux-3.5 PXA PWM driver followed the hardware numbering scheme for the 4 PWMs, while the linux-3.6-rc1 PXA PWM driver has adopted a linear numbering scheme:

Address Hardware 3.5 pwm_id 3.6-rc1 pwm_id
0x40b00000 PWM0 0 0
0x40b00010 PWM2 2 1
0x40c00000 PWM1 1 2
0x40c00010 PWM3 3 3

Quoted 8 lines

The hx4700 backlight uses PWM1 at 0x40c00000. Consequently the pwm_id must be changed from 1 to 2.

Signed-off-by Paul Parsons <[email protected]>
Cc Thierry Reding <[email protected]>
---
  arch/arm/mach-pxa/hx4700.c |    2 +-
  1 files changed, 1 insertions(+), 1 deletions(-)

I wasn't aware of this difference. Sorry for breaking your board. While at it, would you mind converting this to the new style PWM lookup table?

You can find the information in Documentation/pwm.txt, but it should be roughly something like this:

	static struct pwm_lookup hx4700_pwm_lookup[] = {
		PWM_LOOKUP("pxa27x-pwm.1", 0, "pwm-backlight", NULL),
	};
Quoted 8 lines

You can then call:

	pwm_add_table(hx4700_pwm_lookup, ARRAY_SIZE(hx4700_pwm_lookup));

from hx4700_init(). The pwm-backlight driver will then be able to use the new pwm_get() to obtain the PWM device. Note that pwm_request() will go away sometime soon, so this conversion will have to be done anyway. If you do it now I won't have to take care of it anymore. =)

OK, will do.

BTW, it is possible that the changed numbering scheme will also have broken three other PXA27X/PXA3XX boards which use PWM1 or PWM2:

cm-x300
tavorevb
z2

Unfortunately I have no way of testing these.

Regards,
Paul

#6 lore raw

PATCH 1/1 ARM: pxa: hx4700: Fix backlight PWM device number

Quoted 54 lines · Paul Parsons

Hello Thierry,

Quoted 36 lines · Thierry Reding
Quoted 14 lines · Paul Parsons

Recent changes to PXA PWM support changed the PXA27X PWM device numbering scheme.

The linux-3.5 PXA PWM driver followed the hardware numbering scheme for the 4 PWMs, while the linux-3.6-rc1 PXA PWM driver has adopted a linear numbering scheme:

Address         Hardware        3.5 pwm_id      3.6-rc1 pwm_id
0x40b00000      PWM0            0               0
0x40b00010      PWM2            2               1
0x40c00000      PWM1            1               2
0x40c00010      PWM3            3               3
Quoted 8 lines

The hx4700 backlight uses PWM1 at 0x40c00000. Consequently the pwm_id must be changed from 1 to 2.

Signed-off-by Paul Parsons <[email protected]>
Cc Thierry Reding <[email protected]>
---
  arch/arm/mach-pxa/hx4700.c |    2 +-
  1 files changed, 1 insertions(+), 1 deletions(-)

I wasn't aware of this difference. Sorry for breaking your board. While at it, would you mind converting this to the new style PWM lookup table?

You can find the information in Documentation/pwm.txt, but it should be roughly something like this:

        static struct pwm_lookup hx4700_pwm_lookup[] = {
                PWM_LOOKUP("pxa27x-pwm.1", 0, "pwm-backlight", NULL),
        };
Quoted 8 lines

You can then call:

        pwm_add_table(hx4700_pwm_lookup, ARRAY_SIZE(hx4700_pwm_lookup));

from hx4700_init(). The pwm-backlight driver will then be able to use the new pwm_get() to obtain the PWM device. Note that pwm_request() will go away sometime soon, so this conversion will have to be done anyway. If you do it now I won't have to take care of it anymore. =)

OK, will do.

BTW, it is possible that the changed numbering scheme will also have broken three other PXA27X/PXA3XX boards which use PWM1 or PWM2:

Quoted 8 lines

cm-x300
tavorevb
z2

Unfortunately I have no way of testing these.

Regards,
Paul

I have Z2, looks like it's time to test 3.6-rcs on it :)

Regards
Vasily