[PATCH v2 1/6] clk: sunxi-ng: nkm: Support constraints on m/n ratio and parent rate

Frank Oltmanns
2024-02-05T15:23:02Z

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 | 21 +++++++++++++++++++++
drivers/clk/sunxi-ng/ccu_nkm.h | 2 ++
2 files changed, 23 insertions(+)

diff --git a/drivers/clk/sunxi-ng/ccu_nkm.c b/drivers/clk/sunxi-ng/ccu_nkm.c
index 853f84398e2b..1168d894d636 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_m_n_ratio && (m > nkm->max_m_n_ratio * n))
+ return false;
+
+ if (nkm->min_parent_m_ratio && (parent < nkm->min_parent_m_ratio * 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,
@@ -31,6 +45,10 @@ static unsigned long ccu_nkm_find_best_with_parent_adj(struct ccu_common *common
unsigned long tmp_rate, tmp_parent;

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) ||
@@ -64,6 +82,9 @@ 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 (!ccu_nkm_is_valid_rate(common, parent, _n, _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..c409212ee40e 100644
--- a/drivers/clk/sunxi-ng/ccu_nkm.h
+++ b/drivers/clk/sunxi-ng/ccu_nkm.h
@@ -27,6 +27,8 @@ struct ccu_nkm {
struct ccu_mux_internal mux;

unsigned int fixed_post_div;
+ unsigned long max_m_n_ratio;
+ unsigned long min_parent_m_ratio;

struct ccu_common common;
};

--
2.43.0