diff mbox

[v2,12/13] net: ethernet: ti: cpts: calc mult and shift from refclk freq

Message ID 20161128230337.6731-13-grygorii.strashko@ti.com (mailing list archive)
State New, archived
Headers show

Commit Message

Grygorii Strashko Nov. 28, 2016, 11:03 p.m. UTC 
The cyclecounter mult and shift values can be calculated based on the
CPTS rfclk frequency and timekeepnig framework provides required algos
and API's.

Hence, calc mult and shift basing on CPTS rfclk frequency if both
cpts_clock_shift and cpts_clock_mult properties are not provided in DT (the
basis of calculation algorithm is borrowed from
__clocksource_update_freq_scale() commit 7d2f944a2b83 ("clocksource:
Provide a generic mult/shift factor calculation")). After this change
cpts_clock_shift and cpts_clock_mult DT properties will become optional.

Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
---
 Documentation/devicetree/bindings/net/cpsw.txt |  8 +++--
 drivers/net/ethernet/ti/cpts.c                 | 50 ++++++++++++++++++++++----
 2 files changed, 49 insertions(+), 9 deletions(-)

Comments

Richard Cochran Nov. 29, 2016, 10:34 a.m. UTC | #1 
On Mon, Nov 28, 2016 at 05:03:36PM -0600, Grygorii Strashko wrote:
> +static void cpts_calc_mult_shift(struct cpts *cpts)
> +{
> +	u64 frac, maxsec, ns;
> +	u32 freq, mult, shift;
> +
> +	freq = clk_get_rate(cpts->refclk);
> +
> +	/* Calc the maximum number of seconds which we can run before
> +	 * wrapping around.
> +	 */
> +	maxsec = cpts->cc.mask;
> +	do_div(maxsec, freq);
> +	if (maxsec > 600 && cpts->cc.mask > UINT_MAX)
> +		maxsec = 600;

The reason for this test is not obvious.  Why check cc.mask against
UINT_MAX?  Please use the comment to explain it.

Thanks,
Richard
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Grygorii Strashko Nov. 29, 2016, 4:22 p.m. UTC | #2 
On 11/29/2016 04:34 AM, Richard Cochran wrote:
> On Mon, Nov 28, 2016 at 05:03:36PM -0600, Grygorii Strashko wrote:
>> +static void cpts_calc_mult_shift(struct cpts *cpts)
>> +{
>> +	u64 frac, maxsec, ns;
>> +	u32 freq, mult, shift;
>> +
>> +	freq = clk_get_rate(cpts->refclk);
>> +
>> +	/* Calc the maximum number of seconds which we can run before
>> +	 * wrapping around.
>> +	 */
>> +	maxsec = cpts->cc.mask;
>> +	do_div(maxsec, freq);
>> +	if (maxsec > 600 && cpts->cc.mask > UINT_MAX)
>> +		maxsec = 600;
> 
> The reason for this test is not obvious.  Why check cc.mask against
> UINT_MAX?  Please use the comment to explain it.
> 

Yeah. This is copy paste from __clocksource_update_freq_scale(), but
I'm going to limit it to 10 sec for now, because otherwise it will result in too small
mult in case of 64bit counter.

if (maxsec > 10)
	maxsec = 10;
diff mbox

Patch

diff --git a/Documentation/devicetree/bindings/net/cpsw.txt b/Documentation/devicetree/bindings/net/cpsw.txt
index 5ad439f..ebda7c9 100644
--- a/Documentation/devicetree/bindings/net/cpsw.txt
+++ b/Documentation/devicetree/bindings/net/cpsw.txt
@@ -20,8 +20,6 @@  Required properties:
 - slaves		: Specifies number for slaves
 - active_slave		: Specifies the slave to use for time stamping,
 			  ethtool and SIOCGMIIPHY
-- cpts_clock_mult	: Numerator to convert input clock ticks into nanoseconds
-- cpts_clock_shift	: Denominator to convert input clock ticks into nanoseconds
 
 Optional properties:
 - ti,hwmods		: Must be "cpgmac0"
@@ -35,7 +33,11 @@  Optional properties:
 			  For example in dra72x-evm, pcf gpio has to be
 			  driven low so that cpsw slave 0 and phy data
 			  lines are connected via mux.
-
+- cpts_clock_mult	: Numerator to convert input clock ticks into nanoseconds
+- cpts_clock_shift	: Denominator to convert input clock ticks into nanoseconds
+			  Mult and shift will be calculated basing on CPTS
+			  rftclk frequency if both cpts_clock_shift and
+			  cpts_clock_mult properties are not provided.
 
 Slave Properties:
 Required properties:
diff --git a/drivers/net/ethernet/ti/cpts.c b/drivers/net/ethernet/ti/cpts.c
index da3339b..4761d8c 100644
--- a/drivers/net/ethernet/ti/cpts.c
+++ b/drivers/net/ethernet/ti/cpts.c
@@ -406,18 +406,54 @@  void cpts_unregister(struct cpts *cpts)
 }
 EXPORT_SYMBOL_GPL(cpts_unregister);
 
+static void cpts_calc_mult_shift(struct cpts *cpts)
+{
+	u64 frac, maxsec, ns;
+	u32 freq, mult, shift;
+
+	freq = clk_get_rate(cpts->refclk);
+
+	/* Calc the maximum number of seconds which we can run before
+	 * wrapping around.
+	 */
+	maxsec = cpts->cc.mask;
+	do_div(maxsec, freq);
+	if (maxsec > 600 && cpts->cc.mask > UINT_MAX)
+		maxsec = 600;
+
+	if (cpts->cc_mult || cpts->cc.shift)
+		return;
+
+	clocks_calc_mult_shift(&mult, &shift, freq, NSEC_PER_SEC, maxsec);
+
+	cpts->cc_mult = mult;
+	cpts->cc.mult = mult;
+	cpts->cc.shift = shift;
+
+	frac = 0;
+	ns = cyclecounter_cyc2ns(&cpts->cc, freq, cpts->cc.mask, &frac);
+
+	dev_info(cpts->dev,
+		 "CPTS: ref_clk_freq:%u calc_mult:%u calc_shift:%u error:%lld nsec/sec\n",
+		 freq, cpts->cc_mult, cpts->cc.shift, (ns - NSEC_PER_SEC));
+}
+
 static int cpts_of_parse(struct cpts *cpts, struct device_node *node)
 {
 	int ret = -EINVAL;
 	u32 prop;
 
-	if (of_property_read_u32(node, "cpts_clock_mult", &prop))
-		goto  of_error;
-	cpts->cc_mult = prop;
+	cpts->cc_mult = 0;
+	if (!of_property_read_u32(node, "cpts_clock_mult", &prop))
+		cpts->cc_mult = prop;
+
+	cpts->cc.shift = 0;
+	if (!of_property_read_u32(node, "cpts_clock_shift", &prop))
+		cpts->cc.shift = prop;
 
-	if (of_property_read_u32(node, "cpts_clock_shift", &prop))
-		goto  of_error;
-	cpts->cc.shift = prop;
+	if ((cpts->cc_mult && !cpts->cc.shift) ||
+	    (!cpts->cc_mult && cpts->cc.shift))
+		goto of_error;
 
 	return 0;
 
@@ -460,6 +496,8 @@  struct cpts *cpts_create(struct device *dev, void __iomem *regs,
 	cpts->cc.mask = CLOCKSOURCE_MASK(32);
 	cpts->info = cpts_info;
 
+	cpts_calc_mult_shift(cpts);
+
 	return cpts;
 }
 EXPORT_SYMBOL_GPL(cpts_create);