linux-kernel - [PATCH v3 1/1] drivers/rtc: rtc-sun6i: AutoCal Internal OSC Clock

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Date: Thu,  2 May 2024 20:07:36 +0200
From: Alois Fertl <a.fertl@...nline.de>
To: a.zummo@...ertech.it
Cc: alexandre.belloni@...tlin.com,
	wens@...e.org,
	jernej.skrabec@...il.com,
	samuel@...lland.org,
	linux-rtc@...r.kernel.org,
	linux-sunxi@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	Alois Fertl <a.fertl@...nline.de>
Subject: [PATCH v3 1/1] drivers/rtc: rtc-sun6i: AutoCal Internal OSC Clock

I have a M98-8K PLUS Magcubic TV-Box based on the Allwinner H618 SOC.
On board is a Sp6330 wifi/bt module that requires a 32kHz clock to
operate correctly. Without this change the clock from the SOC is
~29kHz and BT module does not start up. The patch enables the Internal
OSC Clock Auto Calibration of the H616/H618 which than provides the
necessary 32kHz and the BT module initializes successfully.
Add a flag and set it for H6 AND H616. The H618 is the same as H616
regarding rtc.

Signed-off-by: Alois Fertl <a.fertl@...nline.de>
---

v1->v2
- add flag and activate for H6 AND H616

v2->v3
- correct findings from review

I was hoping to get some feedback regarding the situation on H6,
where an external 32k crystal can be present.
>From what I understand from the H6 manual there should be no
conflict as one can select which souce will drive the output.
Should certainly be tested but I don`t have H6 hardware.

 drivers/rtc/rtc-sun6i.c | 17 ++++++++++++++++-

 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-sun6i.c b/drivers/rtc/rtc-sun6i.c
index e0b85a0d5645..20e81ccdef29 100644
--- a/drivers/rtc/rtc-sun6i.c
+++ b/drivers/rtc/rtc-sun6i.c
@@ -42,6 +42,11 @@
 
 #define SUN6I_LOSC_CLK_PRESCAL			0x0008
 
+#define SUN6I_LOSC_CLK_AUTO_CAL			0x000c
+#define SUN6I_LOSC_CLK_AUTO_CAL_16MS		BIT(2)
+#define SUN6I_LOSC_CLK_AUTO_CAL_ENABLE		BIT(1)
+#define SUN6I_LOSC_CLK_AUTO_CAL_SEL_CAL		BIT(0)
+
 /* RTC */
 #define SUN6I_RTC_YMD				0x0010
 #define SUN6I_RTC_HMS				0x0014
@@ -126,7 +131,6 @@
  *     registers (R40, H6)
  *   - SYS power domain controls (R40)
  *   - DCXO controls (H6)
- *   - RC oscillator calibration (H6)
  *
  * These functions are not covered by this driver.
  */
@@ -138,6 +142,7 @@ struct sun6i_rtc_clk_data {
 	unsigned int has_losc_en : 1;
 	unsigned int has_auto_swt : 1;
 	unsigned int no_ext_losc : 1;
+	unsigned int has_auto_cal : 1;
 };
 
 #define RTC_LINEAR_DAY	BIT(0)
@@ -268,6 +273,14 @@ static void __init sun6i_rtc_clk_init(struct device_node *node,
 	}
 	writel(reg, rtc->base + SUN6I_LOSC_CTRL);
 
+	if (rtc->data->has_auto_cal) {
+		/* Enable internal OSC clock auto calibration */
+		reg = SUN6I_LOSC_CLK_AUTO_CAL_16MS |
+			SUN6I_LOSC_CLK_AUTO_CAL_ENABLE |
+			SUN6I_LOSC_CLK_AUTO_CAL_SEL_CAL;
+		writel(reg, rtc->base + SUN6I_LOSC_CLK_AUTO_CAL);
+	}
+
 	/* Yes, I know, this is ugly. */
 	sun6i_rtc = rtc;
 
@@ -380,6 +393,7 @@ static const struct sun6i_rtc_clk_data sun50i_h6_rtc_data = {
 	.has_out_clk = 1,
 	.has_losc_en = 1,
 	.has_auto_swt = 1,
+	.has_auto_cal = 1,
 };
 
 static void __init sun50i_h6_rtc_clk_init(struct device_node *node)
@@ -395,6 +409,7 @@ static const struct sun6i_rtc_clk_data sun50i_h616_rtc_data = {
 	.has_prescaler = 1,
 	.has_out_clk = 1,
 	.no_ext_losc = 1,
+	.has_auto_cal = 1,
 };
 
 static void __init sun50i_h616_rtc_clk_init(struct device_node *node)
-- 
2.39.2