On 08/09/2014 21:37, Boris BREZILLON :

On Mon, 8 Sep 2014 21:22:18 +0200
Boris BREZILLON [off-list ref] wrote:

quoted

On Mon, 8 Sep 2014 19:33:38 +0200
Alexandre Belloni [off-list ref] wrote:

quoted

On 03/09/2014 at 10:45:33 +0200, Boris Brezillon wrote :

quoted

The RTT block is using the slow clock and expect it to run at 32KHz.
Now that we moved to the CCF it's better to retain the clk reference so
that the CCF can't disable the slow clock considering it is unused.

Signed-off-by: Boris BREZILLON <redacted>
---
 drivers/rtc/rtc-at91sam9.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/drivers/rtc/rtc-at91sam9.c b/drivers/rtc/rtc-at91sam9.c
index 57014b7..5c5093b 100644
--- a/drivers/rtc/rtc-at91sam9.c
+++ b/drivers/rtc/rtc-at91sam9.c

@@ -21,6 +21,7 @@
 #include <linux/slab.h>
 #include <linux/platform_data/atmel.h>
 #include <linux/io.h>
+#include <linux/clk.h>
 
 /*
  * This driver uses two configurable hardware resources that live in the

@@ -74,6 +75,7 @@ struct sam9_rtc {
 	u32			imr;
 	void __iomem		*gpbr;
 	int 			irq;
+	struct clk		*sclk;
 };
 
 #define rtt_readl(rtc, field) \

@@ -373,6 +375,25 @@ static int at91_rtc_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	/* Retain slow clk if it is specified in the DT.
+	 * Do not complain if slow clk is missing, but check its rate
+	 * if it is available.
+	 */
+	rtc->sclk = devm_clk_get(&pdev->dev, NULL);
+	if (!IS_ERR(rtc->sclk)) {
+		if (clk_get_rate(rtc->sclk) != AT91_SLOW_CLOCK) {

I would not bother doing that check but use the value for MR instead of
AT91_SLOW_CLOCK (see my previous mail).

Unfortunately, we can't get rid of this macro without modifying the
clk_lookup table in several arch/arm/mach-at91/<soc-name>.c files in
order to handle non DT/CCF cases (which will remain until all non DT
boards are moved to DT).

After taking a closer look at what should be modified, I think it's
worth it: there's only 5 impacted files (at91sam9260.c, at91sam9261.c,
at91sam9263.c, at91sam9rl.c and at91sam9g45.c) and adding a clk_lookup
entry is pretty easy.

Moreover we'll end up with a clean driver and won't have to bother
about cleaning it up when dropping non DT boards support.

I vote for this => +1 ;-)

Bye,
-- 
Nicolas Ferre