Re: [PATCH 1/2] rtc: sun6i: Make external 32k oscillator optional

Dne četrtek, 20. februar 2020 ob 18:47:49 CET je Maxime Ripard napisal(a):

On Fri, Feb 14, 2020 at 05:42:13PM +0100, Jernej Škrabec wrote:

quoted

Hi Maxime,

Dne petek, 14. februar 2020 ob 09:14:43 CET je Maxime Ripard napisal(a):

quoted

Hi Jernej,

Thanks for taking care of this

On Thu, Feb 13, 2020 at 10:14:26PM +0100, Jernej Skrabec wrote:

quoted

Some boards, like OrangePi PC2 (H5), OrangePi Plus 2E (H3) and Tanix
TX6
(H6) don't have external 32kHz oscillator. Till H6, it didn't really
matter if external oscillator was enabled because HW detected error
and
fall back to internal one. H6 has same functionality but it's the
first
SoC which have "auto switch bypass" bit documented and always enabled
in
driver. This prevents RTC to work correctly if external crystal is not
present on board. There are other side effects - all peripherals which
depends on this clock also don't work (HDMI CEC for example).

Make clocks property optional. If it is present, select external
oscillator. If not, stay on internal.

Signed-off-by: Jernej Skrabec <redacted>
---

 drivers/rtc/rtc-sun6i.c | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/rtc/rtc-sun6i.c b/drivers/rtc/rtc-sun6i.c
index 852f5f3b3592..538cf7e19034 100644
--- a/drivers/rtc/rtc-sun6i.c
+++ b/drivers/rtc/rtc-sun6i.c

@@ -250,19 +250,17 @@ static void __init sun6i_rtc_clk_init(struct

device_node *node,>

 		writel(reg, rtc->base + SUN6I_LOSC_CTRL);
 	
 	}

-	/* Switch to the external, more precise, oscillator */
-	reg |= SUN6I_LOSC_CTRL_EXT_OSC;
-	if (rtc->data->has_losc_en)
-		reg |= SUN6I_LOSC_CTRL_EXT_LOSC_EN;
+	/* Switch to the external, more precise, oscillator, if present 

*/

quoted

quoted

quoted

+	if (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;
+	}

 	writel(reg, rtc->base + SUN6I_LOSC_CTRL);
 	
 	/* Yes, I know, this is ugly. */
 	sun6i_rtc = rtc;

-	/* Deal with old DTs */
-	if (!of_get_property(node, "clocks", NULL))
-		goto err;
-

Doesn't that prevent the parents to be properly set if there's an
external crystal?

No, why?

Check these two clk_summary:
http://ix.io/2bHY Tanix TX6 (no external crystal)
http://ix.io/2bI2 OrangePi 3 (external crystal present)

I was concerned about the "other" parent. In the case where you don't
have a clocks property (so the check that you are removing), the code
then registers a clock with two parents: the one that we create (the
internal oscillator) and the one coming from the clocks property.

clk_summary only shows the current parent, which is going to be right
with your patch, but in the case where you have no clocks property,
you still (attempts to) register two parents, the second one being
non-functional.

Further looking at it, we might be good because we allocate an array
of two clocks, but only register of_clk_get_parent_count(node) + 1
clocks, so 1 if clocks is missing.

Yes, my patch rely on "of_clk_get_parent_count(node) + 1". If there is no 
property, it will return 1 thus only first parent (internal RC oscilator) will 
be registered.

Anyway, following line:
parents[1] = of_clk_get_parent_name(node, 0);
should evaluate to null. I didn't research further what clk framework does 
with null parent because number of parents will be set to 1 and this null 
value will be ignored anyway.

Still, I think this should be more obvious, through a comment or
shuffling a bit the parent registration maybe?

I think code is in correct order, just maybe a bit more explanation in form of 
comment(s) to make it more obvious how it works for either case.

Best regards,
Jernej



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