On Fri, 02 Dec 2016, Hans de Goede <hdegoede@xxxxxxxxxx> 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@xxxxxxxxx>
>
> 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@xxxxxxxxxx>
> ---
> 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
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