| Message ID | 5062659E.6030104@yahoo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Sep 26, 2012 at 5:17 AM, Paul Parsons <lost.distance@yahoo.com> wrote: > 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 Looks very weird to me. Maybe it would be better to fix pwm numbering scheme to prevent breakage of other machines? Regards Vasily > The hx4700 backlight uses PWM1 at 0x40c00000. Consequently the pwm_id > must be changed from 1 to 2. > > Signed-off-by: Paul Parsons <lost.distance@yahoo.com> > Cc: Thierry Reding <thierry.reding@avionic-design.de> > --- > arch/arm/mach-pxa/hx4700.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/arch/arm/mach-pxa/hx4700.c b/arch/arm/mach-pxa/hx4700.c > index e631198..3720f99 100644 > --- a/arch/arm/mach-pxa/hx4700.c > +++ b/arch/arm/mach-pxa/hx4700.c > @@ -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@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
Hello Vasily, On 26/09/12 07:40, Vasily Khoruzhick wrote: > On Wed, Sep 26, 2012 at 5:17 AM, Paul Parsons <lost.distance@yahoo.com> wrote: >> 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 > > 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
diff --git a/arch/arm/mach-pxa/hx4700.c b/arch/arm/mach-pxa/hx4700.c index e631198..3720f99 100644 --- a/arch/arm/mach-pxa/hx4700.c +++ b/arch/arm/mach-pxa/hx4700.c @@ -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,
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 <lost.distance@yahoo.com> Cc: Thierry Reding <thierry.reding@avionic-design.de> --- arch/arm/mach-pxa/hx4700.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)