Re: [PATCH 2/3] clk: ti: Implement FAPLL set_rate for the synthesizer

From: Tero Kristo
Date: Mon Mar 23 2015 - 09:25:18 EST

On 03/23/2015 12:35 AM, Tony Lindgren wrote:
We can pretty much get any rate out of the FAPLL because of the fractional
divider. Let's first try just adjusting the post divider, and if that is
not enough, then reprogram both the fractional divider and the post divider.

Let's also add a define for the fixed SYNTH_PHASE_K instead of using 8.

Cc: Brian Hutchinson <b.hutchman@xxxxxxxxx>
Cc: Matthijs van Duin <matthijsvanduin@xxxxxxxxx>
Cc: Tero Kristo <t-kristo@xxxxxx>
Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx>
---
drivers/clk/ti/fapll.c | 134 ++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 132 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/ti/fapll.c b/drivers/clk/ti/fapll.c
index 3b5e231..4064f7b 100644
--- a/drivers/clk/ti/fapll.c
+++ b/drivers/clk/ti/fapll.c
@@ -12,6 +12,7 @@
#include <linux/clk-provider.h>
#include <linux/delay.h>
#include <linux/err.h>
+#include <linux/math64.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/clk/ti.h>
@@ -47,6 +48,8 @@
/* Synthesizer frequency register */
#define SYNTH_LDFREQ BIT(31)

+#define SYNTH_PHASE_K 8
+#define SYNTH_MAX_INT_DIV 0xf
#define SYNTH_MAX_DIV_M 0xff

struct fapll_data {
@@ -204,7 +207,7 @@ static unsigned long ti_fapll_synth_recalc_rate(struct clk_hw *hw,
/*
* Synth frequency integer and fractional divider.
* Note that the phase output K is 8, so the result needs
- * to be multiplied by 8.
+ * to be multiplied by SYNTH_PHASE_K.
*/
if (synth->freq) {
u32 v, synth_int_div, synth_frac_div, synth_div_freq;
@@ -215,7 +218,7 @@ static unsigned long ti_fapll_synth_recalc_rate(struct clk_hw *hw,
synth_div_freq = (synth_int_div * 10000000) + synth_frac_div;
rate *= 10000000;
do_div(rate, synth_div_freq);
- rate *= 8;
+ rate *= SYNTH_PHASE_K;
}

/* Synth post-divider M */
@@ -224,11 +227,138 @@ static unsigned long ti_fapll_synth_recalc_rate(struct clk_hw *hw,
return DIV_ROUND_UP_ULL(rate, synth_div_m);
}

+static unsigned long ti_fapll_synth_get_frac_rate(struct clk_hw *hw,
+ unsigned long parent_rate)
+{
+ struct fapll_synth *synth = to_synth(hw);
+ unsigned long current_rate, frac_rate;
+ u32 post_div_m;
+
+ current_rate = ti_fapll_synth_recalc_rate(hw, parent_rate);
+ post_div_m = readl_relaxed(synth->div) & SYNTH_MAX_DIV_M;
+ frac_rate = current_rate * post_div_m;
+
+ return frac_rate;
+}
+
+static u32 ti_fapll_synth_set_frac_rate(struct fapll_synth *synth,
+ unsigned long rate,
+ unsigned long parent_rate)
+{
+ u32 post_div_m, synth_int_div, synth_frac_div, v;
+
+ post_div_m = DIV_ROUND_UP_ULL((u64)parent_rate * SYNTH_PHASE_K, rate);
+ post_div_m = post_div_m / SYNTH_MAX_INT_DIV;
+ if (post_div_m > SYNTH_MAX_DIV_M)
+ return -EINVAL;
+ if (!post_div_m)
+ post_div_m = 1;
+
+ for (; post_div_m < SYNTH_MAX_DIV_M; post_div_m++) {
+ synth_int_div = DIV_ROUND_UP_ULL((u64)parent_rate *
+ SYNTH_PHASE_K *
+ 10000000,
+ rate * post_div_m);
+ synth_frac_div = synth_int_div % 10000000;
+ synth_int_div /= 10000000;
+
+ if (synth_int_div <= SYNTH_MAX_INT_DIV)
+ break;
+ }
+
+ if (synth_int_div > SYNTH_MAX_INT_DIV)
+ return -EINVAL;
+
+ v = readl_relaxed(synth->freq);
+ v &= ~0x1fffffff;
+ v |= (synth_int_div & SYNTH_MAX_INT_DIV) << 24;
+ v |= (synth_frac_div & 0xffffff);

This code is generating these compile time warnings for me:

CC drivers/clk/ti/fapll.o
drivers/clk/ti/fapll.c: In function ‘ti_fapll_synth_set_rate’:
drivers/clk/ti/fapll.c:394:5: warning: ‘synth_int_div’ may be used uninitialized in this function [-Wuninitialized]
drivers/clk/ti/fapll.c:373:18: note: ‘synth_int_div’ was declared here
drivers/clk/ti/fapll.c:400:23: warning: ‘synth_frac_div’ may be used uninitialized in this function [-Wuninitialized]
drivers/clk/ti/fapll.c:373:33: note: ‘synth_frac_div’ was declared here

-Tero


+ v |= SYNTH_LDFREQ;
+ writel_relaxed(v, synth->freq);
+
+ return post_div_m;
+}
+
+static long ti_fapll_synth_round_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long *parent_rate)
+{
+ struct fapll_synth *synth = to_synth(hw);
+ struct fapll_data *fd = synth->fd;
+ unsigned long r;
+
+ if (ti_fapll_clock_is_bypass(fd) || !synth->div || !rate)
+ return -EINVAL;
+
+ /* Only post divider m available with no fractional divider? */
+ if (!synth->freq) {
+ unsigned long frac_rate;
+ u32 synth_post_div_m;
+
+ frac_rate = ti_fapll_synth_get_frac_rate(hw, *parent_rate);
+ synth_post_div_m = DIV_ROUND_UP(frac_rate, rate);
+ r = DIV_ROUND_UP(frac_rate, synth_post_div_m);
+ goto out;
+ }
+
+ r = *parent_rate * SYNTH_PHASE_K;
+ if (rate > r)
+ goto out;
+
+ r = DIV_ROUND_UP_ULL(r, SYNTH_MAX_INT_DIV * SYNTH_MAX_DIV_M);
+ if (rate < r)
+ goto out;
+
+ r = rate;
+out:
+ return r;
+}
+
+static int ti_fapll_synth_set_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long parent_rate)
+{
+ struct fapll_synth *synth = to_synth(hw);
+ struct fapll_data *fd = synth->fd;
+ unsigned long frac_rate, post_rate = 0;
+ u32 post_div_m = 0, v;
+
+ if (ti_fapll_clock_is_bypass(fd) || !synth->div || !rate)
+ return -EINVAL;
+
+ /* Produce the rate with just post divider M? */
+ frac_rate = ti_fapll_synth_get_frac_rate(hw, parent_rate);
+ if (frac_rate < rate) {
+ if (!synth->freq)
+ return -EINVAL;
+ } else {
+ post_div_m = DIV_ROUND_UP(frac_rate, rate);
+ if (post_div_m && (post_div_m <= SYNTH_MAX_DIV_M))
+ post_rate = DIV_ROUND_UP(frac_rate, post_div_m);
+ if (!synth->freq && !post_rate)
+ return -EINVAL;
+ }
+
+ /* Need to recalculate the fractional divider? */
+ if ((post_rate != rate) && synth->freq)
+ post_div_m = ti_fapll_synth_set_frac_rate(synth,
+ rate,
+ parent_rate);
+
+ v = readl_relaxed(synth->div);
+ v &= ~SYNTH_MAX_DIV_M;
+ v |= post_div_m;
+ v |= SYNTH_LDMDIV1;
+ writel_relaxed(v, synth->div);
+
+ return 0;
+}
+
static struct clk_ops ti_fapll_synt_ops = {
.enable = ti_fapll_synth_enable,
.disable = ti_fapll_synth_disable,
.is_enabled = ti_fapll_synth_is_enabled,
.recalc_rate = ti_fapll_synth_recalc_rate,
+ .round_rate = ti_fapll_synth_round_rate,
+ .set_rate = ti_fapll_synth_set_rate,
};

static struct clk * __init ti_fapll_synth_setup(struct fapll_data *fd,


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