Quoting Gregory CLEMENT (2018-09-22 11:17:06)

Does this include need to come first? Preferably local includes come
after any <linux> ones.

+#include <linux/clk-provider.h>
+#include <linux/clk.h>
+#include <linux/init.h>

Is this used?

+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define AP806_CPU_CLUSTER0             0
+#define AP806_CPU_CLUSTER1             1
+#define AP806_CPUS_PER_CLUSTER         2
+#define APN806_CPU1_MASK               0x1
+
+#define APN806_CLUSTER_NUM_OFFSET      8
+#define APN806_CLUSTER_NUM_MASK                (1 << APN806_CLUSTER_NUM_OFFSET)
+
+#define APN806_MAX_DIVIDER             32
+
+/* AP806 CPU DFS register mapping*/
+#define AP806_CA72MP2_0_PLL_CR_0_REG_OFFSET            0x278
+#define AP806_CA72MP2_0_PLL_CR_1_REG_OFFSET            0x280
+#define AP806_CA72MP2_0_PLL_CR_2_REG_OFFSET            0x284
+#define AP806_CA72MP2_0_PLL_SR_REG_OFFSET              0xC94
+
+#define AP806_CA72MP2_0_PLL_CR_CLUSTER_OFFSET          0x14
+#define AP806_PLL_CR_0_CPU_CLK_DIV_RATIO_OFFSET                0
+#define AP806_PLL_CR_0_CPU_CLK_DIV_RATIO_MASK \
+                       (0x3f << AP806_PLL_CR_0_CPU_CLK_DIV_RATIO_OFFSET)
+#define AP806_PLL_CR_0_CPU_CLK_RELOAD_FORCE_OFFSET     24
+#define AP806_PLL_CR_0_CPU_CLK_RELOAD_FORCE_MASK \
+                       (0x1 << AP806_PLL_CR_0_CPU_CLK_RELOAD_FORCE_OFFSET)
+#define AP806_PLL_CR_0_CPU_CLK_RELOAD_RATIO_OFFSET     16
+#define AP806_CA72MP2_0_PLL_RATIO_STATE                        11
+
+#define to_clk(hw) container_of(hw, struct ap_cpu_clk, hw)
+
+/*
+ * struct ap806_clk: CPU cluster clock controller instance
+ * @cluster: Cluster clock controller index
+ * @clk_name: Cluster clock controller name
+ * @dev : Cluster clock device
+ * @hw: HW specific structure of Cluster clock controller
+ * @pll_cr_base: CA72MP2 Register base (Device Sample at Reset register)
+ */
+struct ap_cpu_clk {
+       int cluster;

unsigned?

+       const char *clk_name;
+       struct device *dev;
+       struct clk_hw hw;
+       struct regmap *pll_cr_base;
+};
+
+static struct clk **cluster_clks;
+static struct clk_onecell_data clk_data;

Can you give these some better names that are ap_cpu specific? Grepping
for clk_data will make lots of hits otherwise because they're so
generic.

+
+static unsigned long ap_cpu_clk_recalc_rate(struct clk_hw *hw,
+                                           unsigned long parent_rate)
+{
+       struct ap_cpu_clk *clk = to_clk(hw);
+       unsigned int cpu_clkdiv_reg = AP806_CA72MP2_0_PLL_CR_0_REG_OFFSET +
+               (clk->cluster * AP806_CA72MP2_0_PLL_CR_CLUSTER_OFFSET);

Nitpick: This is pretty unreadable. Can you just declare the variables
up here and then do the assignment later on in the function and avoid
splitting across many lines?

+       int cpu_clkdiv_ratio;
+
+       regmap_read(clk->pll_cr_base, cpu_clkdiv_reg, &cpu_clkdiv_ratio);
+       cpu_clkdiv_ratio &= AP806_PLL_CR_0_CPU_CLK_DIV_RATIO_MASK;
+       cpu_clkdiv_ratio >>= AP806_PLL_CR_0_CPU_CLK_DIV_RATIO_OFFSET;
+
+       return parent_rate / cpu_clkdiv_ratio;
+}
+
+static int ap_cpu_clk_set_rate(struct clk_hw *hw, unsigned long rate,
+                             unsigned long parent_rate)
+{
+       struct ap_cpu_clk *clk = to_clk(hw);
+       int reg, divider = parent_rate / rate;
+       unsigned int cpu_clkdiv_reg, cpu_force_reg, cpu_ratio_reg;
+
+       cpu_clkdiv_reg = AP806_CA72MP2_0_PLL_CR_0_REG_OFFSET +
+               (clk->cluster * AP806_CA72MP2_0_PLL_CR_CLUSTER_OFFSET);
+       cpu_force_reg = AP806_CA72MP2_0_PLL_CR_1_REG_OFFSET +
+               (clk->cluster * AP806_CA72MP2_0_PLL_CR_CLUSTER_OFFSET);
+       cpu_ratio_reg = AP806_CA72MP2_0_PLL_CR_2_REG_OFFSET +
+               (clk->cluster * AP806_CA72MP2_0_PLL_CR_CLUSTER_OFFSET);
+
+       /* 1. Set CPU divider */
+       regmap_update_bits(clk->pll_cr_base, cpu_clkdiv_reg,
+                          AP806_PLL_CR_0_CPU_CLK_DIV_RATIO_MASK, divider);
+
+       /* 2. Set Reload force */
+       regmap_update_bits(clk->pll_cr_base, cpu_force_reg,
+                          AP806_PLL_CR_0_CPU_CLK_RELOAD_FORCE_MASK,
+                          AP806_PLL_CR_0_CPU_CLK_RELOAD_FORCE_MASK);
+
+       /* 3. Set Reload ratio */
+       regmap_update_bits(clk->pll_cr_base, cpu_ratio_reg,
+                          BIT(AP806_PLL_CR_0_CPU_CLK_RELOAD_RATIO_OFFSET),
+                          BIT(AP806_PLL_CR_0_CPU_CLK_RELOAD_RATIO_OFFSET));
+
+
+       /* 4. Wait for stabilizing CPU Clock */
+       do {
+               regmap_read(clk->pll_cr_base,
+                           AP806_CA72MP2_0_PLL_SR_REG_OFFSET,
+                           &reg);
+       } while (!(reg & BIT(clk->cluster * AP806_CA72MP2_0_PLL_RATIO_STATE)));

Use regmap_read_poll_timeout() API here and give some large timeout
value so that we don't get stuck waiting here forever?

+
+       /* 5. Clear Reload ratio */

I'm not sure we really need these comments. They're just saying what the
code is doing, so they don't add much value.

+       regmap_update_bits(clk->pll_cr_base, cpu_ratio_reg,
+                          BIT(AP806_PLL_CR_0_CPU_CLK_RELOAD_RATIO_OFFSET), 0);
+
+       return 0;
+}
+
+
+static long ap_cpu_clk_round_rate(struct clk_hw *hw, unsigned long rate,
+                                unsigned long *parent_rate)
+{
+       int divider = *parent_rate / rate;
+
+       if (divider > APN806_MAX_DIVIDER)
+               divider = APN806_MAX_DIVIDER;

	divider = min(divider, APN806_MAX_DIVIDER);

+
+       return *parent_rate / divider;
+}
+
+static const struct clk_ops ap_cpu_clk_ops = {
+       .recalc_rate    = ap_cpu_clk_recalc_rate,
+       .round_rate     = ap_cpu_clk_round_rate,
+       .set_rate       = ap_cpu_clk_set_rate,
+};
+
+static int ap_cpu_clock_probe(struct platform_device *pdev)
+{
+       int ret, nclusters = 0, cluster_index = 0;
+       struct device *dev = &pdev->dev;
+       struct device_node *dn, *np = dev->of_node;
+       struct ap_cpu_clk *ap_cpu_clk;
+       struct regmap *regmap;
+
+       regmap = syscon_node_to_regmap(np->parent);

Can we just call dev_get_remap() on pdev->dev.parent?

+       if (IS_ERR(regmap)) {
+               pr_err("cannot get pll_cr_base regmap\n");
+               return PTR_ERR(regmap);
+       }
+
+       /*
+        * AP806 has 4 cpus and DFS for AP806 is controlled per
+        * cluster (2 CPUs per cluster), cpu0 and cpu1 are fixed to
+        * cluster0 while cpu2 and cpu3 are fixed to cluster1 whether
+        * they are enabled or not.  Since cpu0 is the boot cpu, then
+        * cluster0 must exist.  If cpu2 or cpu3 is enabled, cluster1
+        * will exist and the cluster number is 2; otherwise the
+        * cluster number is 1.
+        */
+       nclusters = 1;
+       for_each_node_by_type(dn, "cpu") {

Isn't there some sort of for_each_cpu_node() API that can be used here?

+               int cpu, err;
+
+               err = of_property_read_u32(dn, "reg", &cpu);
+               if (WARN_ON(err))
+                       return err;
+
+               /* If cpu2 or cpu3 is enabled */
+               if ((cpu & APN806_CLUSTER_NUM_MASK)) {
+                       nclusters = 2;
+                       break;
+               }
+       }
+       /*
+        * DFS for AP806 is controlled per cluster (2 CPUs per cluster),
+        * so allocate structs per cluster
+        */
+       ap_cpu_clk = devm_kcalloc(dev, nclusters, sizeof(*ap_cpu_clk),
+                                 GFP_KERNEL);
+       if (WARN_ON(!ap_cpu_clk))
+               return -ENOMEM;
+
+       cluster_clks = devm_kcalloc(dev, nclusters, sizeof(*cluster_clks),
+                                   GFP_KERNEL);
+       if (WARN_ON(!cluster_clks))

Drop the WARN_ON please. If allocation fails we'll already get a large
stack trace and messages.

+               return -ENOMEM;
+
+       for_each_node_by_type(dn, "cpu") {
+               char *clk_name = "cpu-cluster-0";
+               struct clk_init_data init;
+               const char *parent_name;
+               struct clk *clk, *parent;
+               int cpu, err;
+
+               err = of_property_read_u32(dn, "reg", &cpu);
+               if (WARN_ON(err))
+                       return err;
+
+               cluster_index = (cpu & APN806_CLUSTER_NUM_MASK);

Nitpick: Drop useless parenthesis please.

+               cluster_index >>= APN806_CLUSTER_NUM_OFFSET;
+
+               /* Initialize once for one cluster */
+               if (cluster_clks[cluster_index])
+                       continue;
+
+               parent = of_clk_get(np, cluster_index);
+               if (IS_ERR(parent)) {
+                       dev_err(dev, "Could not get the clock parent\n");
+                       return -EINVAL;
+               }
+               parent_name =  __clk_get_name(parent);
+               clk_name[12] += cluster_index;
+               ap_cpu_clk[cluster_index].clk_name =
+                       ap_cp_unique_name(dev, np->parent, clk_name);
+               ap_cpu_clk[cluster_index].cluster = cluster_index;
+               ap_cpu_clk[cluster_index].pll_cr_base = regmap;
+               ap_cpu_clk[cluster_index].hw.init = &init;
+               ap_cpu_clk[cluster_index].dev = dev;
+
+               init.name = ap_cpu_clk[cluster_index].clk_name;
+               init.ops = &ap_cpu_clk_ops;
+               init.num_parents = 1;
+               init.parent_names = &parent_name;
+               init.flags = CLK_GET_RATE_NOCACHE;

Can you add a comment why we need NOCACHE here? It isn't clear why this
is important.

+
+               clk = devm_clk_register(dev, &ap_cpu_clk[cluster_index].hw);

Please use the clk_hw based registration APIs.

+               if (IS_ERR(clk))
+                       return PTR_ERR(clk);
+
+               cluster_clks[cluster_index] = clk;
+       }
+
+       clk_data.clk_num = cluster_index + 1;
+       clk_data.clks = cluster_clks;
+
+       ret = of_clk_add_provider(np, of_clk_src_onecell_get, &clk_data);

And the clk_hw based provider APIs.

+       if (ret)
+               dev_err(dev, "failed to register OF clock provider\n");
+
+       return ret;
+}
+