Some WLAN chips attached to a SDIO interface, need a reference clock.

Since this is very common, extend the prseq_simple driver to support
an optional clock that is enabled prior the card power up procedure.

Note: the external clock is optional. Thus an error is not returned
if the clock is not found.
Signed-off-by: NJavier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

Many WLAN attached to a SDIO/MMC interface, needs more than one pin for
their reset sequence. For example, is very common for chips to have two
pins: one for reset and one for power enable.

This patch adds support for more reset pins to the pwrseq_simple driver
and instead hardcoding a fixed number, it uses the of_gpio_named_count()
since the MMC power sequence is only built when CONFIG_OF is enabled.
Signed-off-by: NJavier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: NSrinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

The need for reset GPIOs has several times been pointed out from
erlier posted patchsets. Especially some WLAN chips which are
attached to an SDIO interface may use a GPIO reset.

The reset GPIO is asserted at initialization and prior we start the
power up procedure. The GPIO will be de-asserted right after the power
has been provided to the card, from the ->post_power_on() callback.

Note, the reset GPIO is optional. Thus we don't return an error even if
we can't find a GPIO for the consumer.
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>
Tested-by: NJavier Martinez Canillas <javier.martinez@collabora.co.uk>
Reviewed-by: NJavier Martinez Canillas <javier.martinez@collabora.co.uk>

To add the core part for the MMC power sequence, let's start by adding
initial support for the simple MMC power sequence provider.

In this initial step, the MMC power sequence node are fetched and the
compatible string for the simple MMC power sequence provider are
verified.

At this point we don't parse the node for any properties, but instead
that will be handled from following patches. Since there are no
properties supported yet, let's just implement the ->alloc() and the
->free() callbacks.
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>
Tested-by: NJavier Martinez Canillas <javier.martinez@collabora.co.uk>
Reviewed-by: NJavier Martinez Canillas <javier.martinez@collabora.co.uk>