[PATCH 1/2] pwm: lpss: Make builtin and add lookup-table so that i915 can find the pwm_backlight

[Jani Nikula]

On Fri, 02 Dec 2016, Hans de Goede <hdegoede at redhat.com> wrote:
> The primary consumer of the lpss pwm is the i915 kms driver, but
> currently that driver cannot get the pwm because i915 platforms are
> not using devicetree and pwm-lpss does not call pwm_add_table.
>
> Another problem is that i915 does not support get_pwm returning
> -EPROBE_DEFER and i915's init is very complex and this is almost
> impossible to fix.
>
> This commit changes the PWM_LPSS Kconfig from a tristate to a bool, so
> that when the i915 driver loads the lpss pwm will be available avoiding
> the -EPROBE_DEFER issue. Note that this is identical to how the same
> problem was solved for the pwm-crc driver.

Arguably this solution was worse for pwm-crc than pwm-lpss here, because
bool CONFIG_PWM_CRC depends on INTEL_SOC_PMIC which depends on I2C being
built-in. This one doesn't have all that bad dependencies.

FWIW, both patches are

Acked-by: Jani Nikula <jani.nikula at intel.com>



>
> Being builtin also allows calling pwm_add_table directly from the
> pwm-lpss code, otherwise the pwm_add_table call would need to be put
> somewhere else to ensure it happens before i915 calls pwm_get,
> even if i915 would support -EPROBE_DEFER.
>
> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
> ---
>  drivers/pwm/Kconfig    | 12 +++---------
>  drivers/pwm/pwm-lpss.c | 11 +++++++++++
>  2 files changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index bf01288..cda31ea 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -240,28 +240,22 @@ config PWM_LPC32XX
>  	  will be called pwm-lpc32xx.
>  
>  config PWM_LPSS
> -	tristate
> +	bool
>  
>  config PWM_LPSS_PCI
> -	tristate "Intel LPSS PWM PCI driver"
> +	bool "Intel LPSS PWM PCI driver"
>  	depends on X86 && PCI
>  	select PWM_LPSS
>  	help
>  	  The PCI driver for Intel Low Power Subsystem PWM controller.
>  
> -	  To compile this driver as a module, choose M here: the module
> -	  will be called pwm-lpss-pci.
> -
>  config PWM_LPSS_PLATFORM
> -	tristate "Intel LPSS PWM platform driver"
> +	bool "Intel LPSS PWM platform driver"
>  	depends on X86 && ACPI
>  	select PWM_LPSS
>  	help
>  	  The platform driver for Intel Low Power Subsystem PWM controller.
>  
> -	  To compile this driver as a module, choose M here: the module
> -	  will be called pwm-lpss-platform.
> -
>  config PWM_MESON
>  	tristate "Amlogic Meson PWM driver"
>  	depends on ARCH_MESON
> diff --git a/drivers/pwm/pwm-lpss.c b/drivers/pwm/pwm-lpss.c
> index 72c0bce..b4d8835 100644
> --- a/drivers/pwm/pwm-lpss.c
> +++ b/drivers/pwm/pwm-lpss.c
> @@ -161,6 +161,12 @@ static const struct pwm_ops pwm_lpss_ops = {
>  	.owner = THIS_MODULE,
>  };
>  
> +/* PWM consumed by the Intel GFX */
> +static struct pwm_lookup pwm_lpss_lookup[] = {
> +	PWM_LOOKUP("pwm-lpss", 0, "0000:00:02.0", "pwm_backlight", 0,
> +		   PWM_POLARITY_NORMAL),
> +};
> +
>  struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r,
>  				     const struct pwm_lpss_boardinfo *info)
>  {
> @@ -193,12 +199,17 @@ struct pwm_lpss_chip *pwm_lpss_probe(struct device *dev, struct resource *r,
>  		return ERR_PTR(ret);
>  	}
>  
> +	/* Add lookup table for pwm_backlight */
> +	pwm_lpss_lookup[0].provider = dev_name(dev);
> +	pwm_add_table(pwm_lpss_lookup, ARRAY_SIZE(pwm_lpss_lookup));
> +
>  	return lpwm;
>  }
>  EXPORT_SYMBOL_GPL(pwm_lpss_probe);
>  
>  int pwm_lpss_remove(struct pwm_lpss_chip *lpwm)
>  {
> +	pwm_remove_table(pwm_lpss_lookup, ARRAY_SIZE(pwm_lpss_lookup));
>  	return pwmchip_remove(&lpwm->chip);
>  }
>  EXPORT_SYMBOL_GPL(pwm_lpss_remove);

-- 
Jani Nikula, Intel Open Source Technology Center