brcmfmac: add support for external 32khz clock

Some boards use an external 32khz clock for low-power
mode timing. Make sure the clock is powered on while the chipset
is active.

Signed-off-by: Simon Shields <simon@lineageos.org>

Documentation/devicetree/bindings/net/wireless/brcm,bcm43xx-fmac.txt

@@ -17,6 +17,8 @@ Optional properties:
 	When not specified the device will use in-band SDIO interrupts.
  - interrupt-names : name of the out-of-band interrupt, which must be set
 	to "host-wake".
+ - clocks : external 32khz clock
+ - clock-names : name of the external 32khz clock, must be "32khz"
 
 Example:
 

drivers/net/wireless/broadcom/brcm80211/brcmfmac/common.h

@@ -51,6 +51,7 @@ extern struct brcmf_mp_global_t brcmf_mp_global;
  * @roamoff: Firmware roaming off?
  * @ignore_probe_fail: Ignore probe failure.
  * @country_codes: If available, pointer to struct for translating country codes
+ * @clk: External 32khz clock, if present.
  * @bus: Bus specific platform data. Only SDIO at the mmoment.
  */
 struct brcmf_mp_device {
@@ -60,6 +61,7 @@ struct brcmf_mp_device {
 	bool		roamoff;
 	bool		ignore_probe_fail;
 	struct brcmfmac_pd_cc *country_codes;
+	struct clk *clk;
 	union {
 		struct brcmfmac_sdio_pd sdio;
 	} bus;

drivers/net/wireless/broadcom/brcm80211/brcmfmac/of.c

@@ -13,6 +13,7 @@
  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
+#include <linux/clk.h>
 #include <linux/init.h>
 #include <linux/of.h>
 #include <linux/of_irq.h>
@@ -39,6 +40,10 @@ void brcmf_of_probe(struct device *dev, enum brcmf_bus_type bus_type,
 	if (of_property_read_u32(np, "brcm,drive-strength", &val) == 0)
 		sdio->drive_strength = val;
 
+	settings->clk = devm_clk_get(dev, "32khz");
+	if (IS_ERR(settings->clk))
+		settings->clk = NULL;
+
 	/* make sure there are interrupts defined in the node */
 	if (!of_find_property(np, "interrupts", NULL))
 		return;

drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c

@@ -14,6 +14,7 @@
  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include <linux/clk.h>
 #include <linux/types.h>
 #include <linux/atomic.h>
 #include <linux/kernel.h>
@@ -3853,6 +3854,11 @@ brcmf_sdio_probe_attach(struct brcmf_sdio *bus)
 		brcmf_err("Failed to get device parameters\n");
 		goto fail;
 	}
+
+	/* enable external 32khz clock, if present */
+	if (sdiodev->settings->clk)
+		clk_prepare_enable(sdiodev->settings->clk);
+
 	/* platform specific configuration:
 	 *   alignments must be at least 4 bytes for ADMA
 	 */
@@ -4270,6 +4276,10 @@ void brcmf_sdio_remove(struct brcmf_sdio *bus)
 			}
 			brcmf_chip_detach(bus->ci);
 		}
+
+		if (bus->sdiodev->settings->clk)
+			clk_disable_unprepare(bus->sdiodev->settings->clk);
+
 		if (bus->sdiodev->settings)
 			brcmf_release_module_param(bus->sdiodev->settings);