[PATCH 08/15] Bluetooth: hci_bcm: Add support for LPO clock

Chen-Yu Tsai
2018-11-07T10:13:01Z

The Broadcom Bluetooth controllers support a secondary LPO clock at
32.768 kHz. This external clock provides low power timing, and also
a way to detect the frequency of the main reference clock. On many
designs without NVRAM and a non-default reference clock, this must
be used or the controller will not function correctly.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
---
drivers/bluetooth/hci_bcm.c | 41 ++++++++++++++++++++++++++++++++-----
1 file changed, 36 insertions(+), 5 deletions(-)

diff --git a/drivers/bluetooth/hci_bcm.c b/drivers/bluetooth/hci_bcm.c
index 7556f8fac8aa..ab6e527952a9 100644
--- a/drivers/bluetooth/hci_bcm.c
+++ b/drivers/bluetooth/hci_bcm.c
@@ -72,7 +72,8 @@
* @btpu: Apple ACPI method to drive BT_REG_ON pin high ("Bluetooth Power Up")
* @btpd: Apple ACPI method to drive BT_REG_ON pin low ("Bluetooth Power Down")
* @txco_clk: external reference frequency clock used by Bluetooth device
- * @clk_enabled: whether @txco_clk is prepared and enabled
+ * @lpo_clk: external LPO clock used by Bluetooth device
+ * @clk_enabled: whether clocks are prepared and enabled
* @init_speed: default baudrate of Bluetooth device;
* the host UART is initially set to this baudrate so that
* it can configure the Bluetooth device for @oper_speed
@@ -103,6 +104,7 @@ struct bcm_device {
#endif

struct clk *txco_clk;
+ struct clk *lpo_clk;
bool clk_enabled;

u32 init_speed;
@@ -215,21 +217,34 @@ static int bcm_gpio_set_power(struct bcm_device *dev, bool powered)
int err;

if (powered && !dev->clk_enabled) {
- err = clk_prepare_enable(dev->txco_clk);
+ /* LPO clock needs to be 32.768 kHz */
+ err = clk_set_rate(dev->lpo_clk, 32768);
+ if (err) {
+ dev_err(dev->dev, "Could not set LPO clock rate\n");
+ return err;
+ }
+
+ err = clk_prepare_enable(dev->lpo_clk);
if (err)
return err;
+
+ err = clk_prepare_enable(dev->txco_clk);
+ if (err)
+ goto err_lpo_clk_disable;
}

err = dev->set_shutdown(dev, powered);
if (err)
- goto err_clk_disable;
+ goto err_txco_clk_disable;

err = dev->set_device_wakeup(dev, powered);
if (err)
goto err_revert_shutdown;

- if (!powered && dev->clk_enabled)
+ if (!powered && dev->clk_enabled) {
clk_disable_unprepare(dev->txco_clk);
+ clk_disable_unprepare(dev->lpo_clk);
+ }

dev->clk_enabled = powered;

@@ -237,9 +252,12 @@ static int bcm_gpio_set_power(struct bcm_device *dev, bool powered)

err_revert_shutdown:
dev->set_shutdown(dev, !powered);
-err_clk_disable:
+err_txco_clk_disable:
if (powered && !dev->clk_enabled)
clk_disable_unprepare(dev->txco_clk);
+err_lpo_clk_disable:
+ if (powered && !dev->clk_enabled)
+ clk_disable_unprepare(dev->lpo_clk);
return err;
}

@@ -934,6 +952,19 @@ static int bcm_get_resources(struct bcm_device *dev)
if (IS_ERR(dev->txco_clk))
dev->txco_clk = NULL;

+ dev->lpo_clk = devm_clk_get(dev->dev, "lpo");
+ if (IS_ERR(dev->lpo_clk) && PTR_ERR(dev->lpo_clk) == -EPROBE_DEFER)
+ return PTR_ERR(dev->lpo_clk);
+
+ if (IS_ERR(dev->lpo_clk))
+ dev->lpo_clk = NULL;
+
+ /* Check if we accidentally fetched the lpo clock twice */
+ if (dev->lpo_clk && clk_is_match(dev->lpo_clk, dev->txco_clk)) {
+ devm_clk_put(dev->dev, dev->txco_clk);
+ dev->txco_clk = NULL;
+ }
+
dev->device_wakeup = devm_gpiod_get_optional(dev->dev, "device-wakeup",
GPIOD_OUT_LOW);
if (IS_ERR(dev->device_wakeup))
--
2.19.1