[PATCH v4 3/5] clk: sunxi-ng: nkm: Support constraints on m/n ratio and parent rate

[Frank Oltmanns]

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.

Reviewed-by: Jernej Skrabec <jernej.skra...@gmail.com>
Signed-off-by: Frank Oltmanns <fr...@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;
 };

-- 
2.44.0