linux-kernel - [PATCH v8 06/11] rtc: sun6i: Add support for RTCs without external LOSCs

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Date:   Fri, 23 Jul 2021 16:38:33 +0100
From:   Andre Przywara <andre.przywara@....com>
To:     Maxime Ripard <mripard@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>
Cc:     Rob Herring <robh@...nel.org>, Icenowy Zheng <icenowy@...c.io>,
        Samuel Holland <samuel@...lland.org>,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...glegroups.com,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Ondrej Jirman <megous@...ous.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        linux-rtc@...r.kernel.org
Subject: [PATCH v8 06/11] rtc: sun6i: Add support for RTCs without external LOSCs

Some newer Allwinner RTCs (for instance the one in the H616 SoC) lack
a pin for an external 32768 Hz oscillator. As a consequence, this LOSC
can't be selected as the RTC clock source, and we must rely on the
internal RC oscillator.
To allow additions of clocks to the RTC node, add a feature bit to ignore
any provided clocks for now (the current code would think this is the
external LOSC). Later DTs and code can then for instance add the PLL
based clock input, and older kernel won't get confused.

Signed-off-by: Andre Przywara <andre.przywara@....com>
---
 drivers/rtc/rtc-sun6i.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/rtc/rtc-sun6i.c b/drivers/rtc/rtc-sun6i.c
index f0ee20bfdccb..ef2b1027ce4c 100644
--- a/drivers/rtc/rtc-sun6i.c
+++ b/drivers/rtc/rtc-sun6i.c
@@ -134,6 +134,7 @@ struct sun6i_rtc_clk_data {
 	unsigned int export_iosc : 1;
 	unsigned int has_losc_en : 1;
 	unsigned int has_auto_swt : 1;
+	unsigned int no_ext_losc : 1;
 };
 
 #define RTC_LINEAR_DAY	BIT(0)
@@ -256,7 +257,7 @@ static void __init sun6i_rtc_clk_init(struct device_node *node,
 	}
 
 	/* Switch to the external, more precise, oscillator, if present */
-	if (of_get_property(node, "clocks", NULL)) {
+	if (!rtc->data->no_ext_losc && of_get_property(node, "clocks", NULL)) {
 		reg |= SUN6I_LOSC_CTRL_EXT_OSC;
 		if (rtc->data->has_losc_en)
 			reg |= SUN6I_LOSC_CTRL_EXT_LOSC_EN;
@@ -282,14 +283,19 @@ static void __init sun6i_rtc_clk_init(struct device_node *node,
 	}
 
 	parents[0] = clk_hw_get_name(rtc->int_osc);
-	/* If there is no external oscillator, this will be NULL and ... */
-	parents[1] = of_clk_get_parent_name(node, 0);
+	if (rtc->data->no_ext_losc) {
+		parents[1] = NULL;
+		init.num_parents = 1;
+	} else {
+		/* If there is no external oscillator, this will be NULL and */
+		parents[1] = of_clk_get_parent_name(node, 0);
+		/* ... number of clock parents will be 1. */
+		init.num_parents = of_clk_get_parent_count(node) + 1;
+	}
 
 	rtc->hw.init = &init;
 
 	init.parent_names = parents;
-	/* ... number of clock parents will be 1. */
-	init.num_parents = of_clk_get_parent_count(node) + 1;
 	of_property_read_string_index(node, "clock-output-names", 0,
 				      &init.name);
 
-- 
2.17.6