[PATCH 1/5] clk: sunxi-ng: nkm: Support constraints on m/n ratio and parent rate

Frank Oltmanns
2023-12-18T13:36:52Z

The Allwinner A64 manual lists the following constraints for the
PLL-MIPI clock:
- M/N >= 3
- (PLL_VIDEO0)/M >= 24MHz

The PLL-MIPI clock is implemented as ccu_nkm. Therefore, add support for
these constraints.

Signed-off-by: Frank Oltmanns <frank@oltmanns.dev>
---
drivers/clk/sunxi-ng/ccu_nkm.c | 23 +++++++++++++++++++++++
drivers/clk/sunxi-ng/ccu_nkm.h | 8 ++++++++
2 files changed, 31 insertions(+)

diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c
index eed64547ad42..2af5c1ebd527 100644
--- a/drivers/clk/sunxi-ng/ccu_nkm.c
+++ b/drivers/clk/sunxi-ng/ccu_nkm.c
@@ -16,6 +16,20 @@ struct _ccu_nkm {
unsigned long m, min_m, max_m;
};

+static bool ccu_nkm_is_valid_rate(struct ccu_common *common, unsigned long parent,
+ unsigned long n, unsigned long m)
+{
+ struct ccu_nkm *nkm = container_of(common, struct ccu_nkm, common);
+
+ if (nkm->max_mn_ratio && (m > nkm->max_mn_ratio * n))
+ return false;
+
+ if (nkm->parent_wo_nk && (parent < nkm->parent_wo_nk * m))
+ return false;
+
+ return true;
+}
+
static unsigned long ccu_nkm_find_best_with_parent_adj(struct ccu_common *common,
struct clk_hw *parent_hw,
unsigned long *parent, unsigned long rate,
@@ -32,6 +46,9 @@ static unsigned long ccu_nkm_find_best_with_parent_adj(struct ccu_common *common

tmp_parent = clk_hw_round_rate(parent_hw, rate * _m / (_n * _k));

+ if (!ccu_nkm_is_valid_rate(common, tmp_parent, _n, _m))
+ continue;
+
tmp_rate = tmp_parent * _n * _k / _m;

if (ccu_is_better_rate(common, rate, tmp_rate, best_rate) ||
@@ -65,6 +82,12 @@ static unsigned long ccu_nkm_find_best(unsigned long parent, unsigned long rate,
for (_k = nkm->min_k; _k <= nkm->max_k; _k++) {
for (_n = nkm->min_n; _n <= nkm->max_n; _n++) {
for (_m = nkm->min_m; _m <= nkm->max_m; _m++) {
+ if ((common->reg == 0x040) && (_m > 3 * _n))
+ break;
+
+ if ((common->reg == 0x040) && (parent < 24000000 * _m))
+ continue;
+
unsigned long tmp_rate;

tmp_rate = parent * _n * _k / _m;
diff --git a/drivers/clk/sunxi-ng/ccu_nkm.h b/drivers/clk/sunxi-ng/ccu_nkm.h
index 6601defb3f38..d3d3eaf55faf 100644
--- a/drivers/clk/sunxi-ng/ccu_nkm.h
+++ b/drivers/clk/sunxi-ng/ccu_nkm.h
@@ -16,6 +16,12 @@
* struct ccu_nkm - Definition of an N-K-M clock
*
* Clocks based on the formula parent * N * K / M
+ *
+ * @max_mn_ratio: Maximum value for M / N.
+ * @parent_wo_nk: The minimum rate the parent must provide after applying the divisor,
+ * but without applying the multipliers, i.e. the contstraint
+ * (parent rate)/M >= parent_wo_nk
+ * must be fulfilled.
*/
struct ccu_nkm {
u32 enable;
@@ -27,6 +33,8 @@ struct ccu_nkm {
struct ccu_mux_internal mux;

unsigned int fixed_post_div;
+ unsigned long max_mn_ratio;
+ unsigned long parent_wo_nk;

struct ccu_common common;
};

--
2.43.0