RPi/RPi2: add kernel patch to fix I2S clock

rpi-4.9.y commit 76527b4e6a5dbe55e0b2d8ab533c2388b36c86be

This fixes 48kHz samplerate not working on HifiBerry Amp+.
See https://github.com/raspberrypi/linux/issues/2016

This patch can be dropped on the next RPi kernel bump.

Signed-off-by: Matthias Reichl <hias@horus.com>

projects/RPi/patches/linux/linux-02-RPi_clk_fix.patch

@@ -0,0 +1,127 @@
+From 76527b4e6a5dbe55e0b2d8ab533c2388b36c86be Mon Sep 17 00:00:00 2001
+From: Phil Elwell <phil@raspberrypi.org>
+Date: Mon, 22 May 2017 13:56:41 +0100
+Subject: [PATCH] clk: bcm2835: Minimise clock jitter for PCM clock
+
+Fractional clock dividers generate accurate average frequencies but
+with jitter, particularly when the integer divisor is small.
+
+Introduce a new metric of clock accuracy to penalise clocks with a good
+average but worse jitter compared to clocks with an average which is no
+better but with lower jitter. The metric is the ideal rate minus the
+worse deviation from that ideal using the nearest integer divisors.
+
+Use this metric for parent selection for clocks requiring low jitter
+(currently just PCM).
+
+Signed-off-by: Phil Elwell <phil@raspberrypi.org>
+---
+ drivers/clk/bcm/clk-bcm2835.c | 39 ++++++++++++++++++++++++++++++++++-----
+ 1 file changed, 34 insertions(+), 5 deletions(-)
+
+diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
+index c24b4de..db3ba74 100644
+--- a/drivers/clk/bcm/clk-bcm2835.c
++++ b/drivers/clk/bcm/clk-bcm2835.c
+@@ -534,6 +534,7 @@ struct bcm2835_clock_data {
+ 
+ 	bool is_vpu_clock;
+ 	bool is_mash_clock;
++	bool low_jitter;
+ 
+ 	u32 tcnt_mux;
+ };
+@@ -1154,7 +1155,8 @@ static unsigned long bcm2835_clock_choose_div_and_prate(struct clk_hw *hw,
+ 							int parent_idx,
+ 							unsigned long rate,
+ 							u32 *div,
+-							unsigned long *prate)
++							unsigned long *prate,
++							unsigned long *avgrate)
+ {
+ 	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
+ 	struct bcm2835_cprman *cprman = clock->cprman;
+@@ -1166,11 +1168,33 @@ static unsigned long bcm2835_clock_choose_div_and_prate(struct clk_hw *hw,
+ 	parent = clk_hw_get_parent_by_index(hw, parent_idx);
+ 
+ 	if (!(BIT(parent_idx) & data->set_rate_parent)) {
++		unsigned long tmp_rate;
++
+ 		*prate = clk_hw_get_rate(parent);
+ 		*div = bcm2835_clock_choose_div(hw, rate, *prate, true);
+ 
+-		return bcm2835_clock_rate_from_divisor(clock, *prate,
+-						       *div);
++		tmp_rate = bcm2835_clock_rate_from_divisor(clock, *prate, *div);
++		*avgrate = tmp_rate;
++
++		if (data->low_jitter && (*div & CM_DIV_FRAC_MASK)) {
++			unsigned long high, low;
++			u32 idiv = *div & ~CM_DIV_FRAC_MASK;
++
++			high = bcm2835_clock_rate_from_divisor(clock, *prate,
++							       idiv);
++			idiv += CM_DIV_FRAC_MASK + 1;
++			low = bcm2835_clock_rate_from_divisor(clock, *prate,
++							      idiv);
++
++			/* Return a value which is the maximum deviation
++			 * below the ideal rate, for use as a metric.
++			 */
++			if ((tmp_rate - low) < (high - tmp_rate))
++				tmp_rate = low;
++			else
++				tmp_rate -= high - tmp_rate;
++		}
++		return tmp_rate;
+ 	}
+ 
+ 	if (data->frac_bits)
+@@ -1197,6 +1221,7 @@ static unsigned long bcm2835_clock_choose_div_and_prate(struct clk_hw *hw,
+ 
+ 	*div = curdiv << CM_DIV_FRAC_BITS;
+ 	*prate = curdiv * best_rate;
++	*avgrate = best_rate;
+ 
+ 	return best_rate;
+ }
+@@ -1208,6 +1233,7 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw,
+ 	bool current_parent_is_pllc;
+ 	unsigned long rate, best_rate = 0;
+ 	unsigned long prate, best_prate = 0;
++	unsigned long avgrate, best_avgrate = 0;
+ 	size_t i;
+ 	u32 div;
+ 
+@@ -1232,11 +1258,13 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw,
+ 			continue;
+ 
+ 		rate = bcm2835_clock_choose_div_and_prate(hw, i, req->rate,
+-							  &div, &prate);
++							  &div, &prate,
++							  &avgrate);
+ 		if (rate > best_rate && rate <= req->rate) {
+ 			best_parent = parent;
+ 			best_prate = prate;
+ 			best_rate = rate;
++			best_avgrate = avgrate;
+ 		}
+ 	}
+ 
+@@ -1246,7 +1274,7 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw,
+ 	req->best_parent_hw = best_parent;
+ 	req->best_parent_rate = best_prate;
+ 
+-	req->rate = best_rate;
++	req->rate = best_avgrate;
+ 
+ 	return 0;
+ }
+@@ -2061,6 +2089,7 @@ static const struct bcm2835_clk_desc clk_desc_array[] = {
+ 		.int_bits = 12,
+ 		.frac_bits = 12,
+ 		.is_mash_clock = true,
++		.low_jitter = true,
+ 		.parents = bcm2835_pcm_per_parents,
+ 		.tcnt_mux = 23),
+ 	[BCM2835_CLOCK_PWM]	= REGISTER_PER_CLK(

projects/RPi2/patches/linux/linux-02-RPi_clk_fix.patch

@@ -0,0 +1,127 @@
+From 76527b4e6a5dbe55e0b2d8ab533c2388b36c86be Mon Sep 17 00:00:00 2001
+From: Phil Elwell <phil@raspberrypi.org>
+Date: Mon, 22 May 2017 13:56:41 +0100
+Subject: [PATCH] clk: bcm2835: Minimise clock jitter for PCM clock
+
+Fractional clock dividers generate accurate average frequencies but
+with jitter, particularly when the integer divisor is small.
+
+Introduce a new metric of clock accuracy to penalise clocks with a good
+average but worse jitter compared to clocks with an average which is no
+better but with lower jitter. The metric is the ideal rate minus the
+worse deviation from that ideal using the nearest integer divisors.
+
+Use this metric for parent selection for clocks requiring low jitter
+(currently just PCM).
+
+Signed-off-by: Phil Elwell <phil@raspberrypi.org>
+---
+ drivers/clk/bcm/clk-bcm2835.c | 39 ++++++++++++++++++++++++++++++++++-----
+ 1 file changed, 34 insertions(+), 5 deletions(-)
+
+diff --git a/drivers/clk/bcm/clk-bcm2835.c b/drivers/clk/bcm/clk-bcm2835.c
+index c24b4de..db3ba74 100644
+--- a/drivers/clk/bcm/clk-bcm2835.c
++++ b/drivers/clk/bcm/clk-bcm2835.c
+@@ -534,6 +534,7 @@ struct bcm2835_clock_data {
+ 
+ 	bool is_vpu_clock;
+ 	bool is_mash_clock;
++	bool low_jitter;
+ 
+ 	u32 tcnt_mux;
+ };
+@@ -1154,7 +1155,8 @@ static unsigned long bcm2835_clock_choose_div_and_prate(struct clk_hw *hw,
+ 							int parent_idx,
+ 							unsigned long rate,
+ 							u32 *div,
+-							unsigned long *prate)
++							unsigned long *prate,
++							unsigned long *avgrate)
+ {
+ 	struct bcm2835_clock *clock = bcm2835_clock_from_hw(hw);
+ 	struct bcm2835_cprman *cprman = clock->cprman;
+@@ -1166,11 +1168,33 @@ static unsigned long bcm2835_clock_choose_div_and_prate(struct clk_hw *hw,
+ 	parent = clk_hw_get_parent_by_index(hw, parent_idx);
+ 
+ 	if (!(BIT(parent_idx) & data->set_rate_parent)) {
++		unsigned long tmp_rate;
++
+ 		*prate = clk_hw_get_rate(parent);
+ 		*div = bcm2835_clock_choose_div(hw, rate, *prate, true);
+ 
+-		return bcm2835_clock_rate_from_divisor(clock, *prate,
+-						       *div);
++		tmp_rate = bcm2835_clock_rate_from_divisor(clock, *prate, *div);
++		*avgrate = tmp_rate;
++
++		if (data->low_jitter && (*div & CM_DIV_FRAC_MASK)) {
++			unsigned long high, low;
++			u32 idiv = *div & ~CM_DIV_FRAC_MASK;
++
++			high = bcm2835_clock_rate_from_divisor(clock, *prate,
++							       idiv);
++			idiv += CM_DIV_FRAC_MASK + 1;
++			low = bcm2835_clock_rate_from_divisor(clock, *prate,
++							      idiv);
++
++			/* Return a value which is the maximum deviation
++			 * below the ideal rate, for use as a metric.
++			 */
++			if ((tmp_rate - low) < (high - tmp_rate))
++				tmp_rate = low;
++			else
++				tmp_rate -= high - tmp_rate;
++		}
++		return tmp_rate;
+ 	}
+ 
+ 	if (data->frac_bits)
+@@ -1197,6 +1221,7 @@ static unsigned long bcm2835_clock_choose_div_and_prate(struct clk_hw *hw,
+ 
+ 	*div = curdiv << CM_DIV_FRAC_BITS;
+ 	*prate = curdiv * best_rate;
++	*avgrate = best_rate;
+ 
+ 	return best_rate;
+ }
+@@ -1208,6 +1233,7 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw,
+ 	bool current_parent_is_pllc;
+ 	unsigned long rate, best_rate = 0;
+ 	unsigned long prate, best_prate = 0;
++	unsigned long avgrate, best_avgrate = 0;
+ 	size_t i;
+ 	u32 div;
+ 
+@@ -1232,11 +1258,13 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw,
+ 			continue;
+ 
+ 		rate = bcm2835_clock_choose_div_and_prate(hw, i, req->rate,
+-							  &div, &prate);
++							  &div, &prate,
++							  &avgrate);
+ 		if (rate > best_rate && rate <= req->rate) {
+ 			best_parent = parent;
+ 			best_prate = prate;
+ 			best_rate = rate;
++			best_avgrate = avgrate;
+ 		}
+ 	}
+ 
+@@ -1246,7 +1274,7 @@ static int bcm2835_clock_determine_rate(struct clk_hw *hw,
+ 	req->best_parent_hw = best_parent;
+ 	req->best_parent_rate = best_prate;
+ 
+-	req->rate = best_rate;
++	req->rate = best_avgrate;
+ 
+ 	return 0;
+ }
+@@ -2061,6 +2089,7 @@ static const struct bcm2835_clk_desc clk_desc_array[] = {
+ 		.int_bits = 12,
+ 		.frac_bits = 12,
+ 		.is_mash_clock = true,
++		.low_jitter = true,
+ 		.parents = bcm2835_pcm_per_parents,
+ 		.tcnt_mux = 23),
+ 	[BCM2835_CLOCK_PWM]	= REGISTER_PER_CLK(