Re: [PATCH 2/3] clk: conf: Support assigned-clock-sscs
From: Dan Carpenter <hidden>
Date: 2025-08-13 05:48:51
Also in:
arm-scmi, linux-clk, lkml
On Tue, Aug 12, 2025 at 08:17:06PM +0800, Peng Fan wrote:
quoted hunk ↗ jump to hunk
Parse the Spread Spectrum Configuration(SSC) from device tree and configure them before using the clock. Each SSC is three u32 elements which means '<modfreq spreaddepth modmethod>', so assigned-clock-sscs is an array of multiple three u32 elements. Signed-off-by: Peng Fan <peng.fan@nxp.com> --- drivers/clk/clk-conf.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 70 insertions(+)diff --git a/drivers/clk/clk-conf.c b/drivers/clk/clk-conf.c index 303a0bb26e54a95655ce094a35b989c97ebc6fd8..81a2c1f8ca4c44df2c54c1e51f800f533c9453b3 100644 --- a/drivers/clk/clk-conf.c +++ b/drivers/clk/clk-conf.c@@ -155,6 +155,72 @@ static int __set_clk_rates(struct device_node *node, bool clk_supplier) return 0; } +static int __set_clk_spread_spectrum(struct device_node *node, bool clk_supplier) +{ + u32 *sscs __free(kfree) = NULL; + u32 elem_size = sizeof(u32) * 3; + struct of_phandle_args clkspec; + int rc, count, index; + struct clk *clk; + + /* modfreq, spreadPercent, modmethod */ + count = of_property_count_elems_of_size(node, "assigned-clock-sscs", elem_size); + if (count > 0) { + sscs = kcalloc(count, elem_size, GFP_KERNEL); + if (!sscs) + return -ENOMEM; + rc = of_property_read_u32_array(node, + "assigned-clock-sscs", + sscs, count * 3); + } else { + return 0; + } + + if (rc) + return rc;
Nit pick: Please, flip these conditions around. count = of_property_count_elems_of_size(node, "assigned-clock-sscs", elem_size); if (count <= 0) return 0; sscs = kcalloc(count, elem_size, GFP_KERNEL); if (!sscs) return -ENOMEM; rc = of_property_read_u32_array(node, "assigned-clock-sscs", sscs, count * 3); if (rc) return rc;
+
+ for (index = 0; index < count; index++) {
+ u32 modfreq_hz = sscs[index * 3], spread_bp = sscs[index * 3 + 1];
+ u32 method = sscs[index * 3 + 2];
This math would be nicer if you created a struct:
struct spread_config {
u32 modfreq_hz;
u32 spread_depth;
u32 method;
};
Then you could use that instead of sscs.
for (i = 0; i < count; i++) {
struct spread_config *conf = &configs[i];
struct clk_hw *hw;
if (!conf->modfreq_hz && !conf->spread_depth && !conf->method)
continue;
+ struct clk_hw *hw;
+
+ if (modfreq_hz || spread_bp || method) {
+ rc = of_parse_phandle_with_args(node, "assigned-clocks",
+ "#clock-cells", index, &clkspec);
+ if (rc < 0) {
+ /* skip empty (null) phandles */
+ if (rc == -ENOENT)
+ continue;
+ else
+ return rc;
+ }
+
+ if (clkspec.np == node && !clk_supplier) {Could you add a comment for this condition? It's strange to me that we don't iterate through the whole array. regards, dan carpenter
+ of_node_put(clkspec.np);
+ return 0;
+ }
+
+ clk = of_clk_get_from_provider(&clkspec);
+ of_node_put(clkspec.np);
+ if (IS_ERR(clk)) {
+ if (PTR_ERR(clk) != -EPROBE_DEFER)
+ pr_warn("clk: couldn't get clock %d for %pOF\n",
+ index, node);
+ return PTR_ERR(clk);
+ }
+
+ hw = __clk_get_hw(clk);
+ rc = clk_hw_set_spread_spectrum(hw, modfreq_hz, spread_bp, method);
+ if (rc < 0)
+ pr_err("clk: couldn't set %s clk spread spectrum %u %u %u: %d\n",
+ __clk_get_name(clk), modfreq_hz, spread_bp, method, rc);
+ clk_put(clk);
+ }
+ }
+
+ return 0;
+}