The algorithm in the ast2500_calc_clock_config() routine suffers from
integer rounding and the requested rate does not get the appropriate
set of Numerator, Denumerator, Post Divider parameters.
This is the case for the D2-PLL clock used by the MAC controllers in
RGMII mode. The requested rated is 250MHz but a 251MHz is assigned.
The easiest way to fix this problem is to introduce an array of clock
settings defining the N, M, P parameters for well known frequencies
used by the Aspeed SoC.
Signed-off-by: Cédric Le Goater <c...@kaod.org>
Reviewed-by: Simon Glass <s...@chromium.org>
---
drivers/clk/aspeed/clk_ast2500.c | 38 ++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)
diff --git a/drivers/clk/aspeed/clk_ast2500.c b/drivers/clk/aspeed/clk_ast2500.c
index 2182320f607f..dbee13a18297 100644
--- a/drivers/clk/aspeed/clk_ast2500.c
+++ b/drivers/clk/aspeed/clk_ast2500.c
@@ -165,6 +165,35 @@ static ulong ast2500_clk_get_rate(struct clk *clk)
return rate;
}
+struct ast2500_clock_config {
+ ulong input_rate;
+ ulong rate;
+ struct ast2500_div_config cfg;
+};
+
+static const struct ast2500_clock_config ast2500_clock_config_defaults[] = {
+ { 24000000, 250000000, { .num = 124, .denum = 1, .post_div = 5 } },
+};
+
+static bool ast2500_get_clock_config_default(ulong input_rate,
+ ulong requested_rate,
+ struct ast2500_div_config *cfg)
+{
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(ast2500_clock_config_defaults); i++) {
+ const struct ast2500_clock_config *default_cfg =
+ &ast2500_clock_config_defaults[i];
+ if (default_cfg->input_rate == input_rate &&
+ default_cfg->rate == requested_rate) {
+ *cfg = default_cfg->cfg;
+ return true;
+ }
+ }
+
+ return false;
+}
+
/*
* @input_rate - the rate of input clock in Hz
* @requested_rate - desired output rate in Hz
@@ -189,6 +218,12 @@ static ulong ast2500_calc_clock_config(ulong input_rate,
ulong requested_rate,
ulong delta = rate_khz;
ulong new_rate_khz = 0;
+ /*
+ * Look for a well known frequency first.
+ */
+ if (ast2500_get_clock_config_default(input_rate, requested_rate, cfg))
+ return requested_rate;
+
for (; it.denum <= max_vals.denum; ++it.denum) {
for (it.post_div = 0; it.post_div <= max_vals.post_div;
++it.post_div) {
@@ -318,6 +353,9 @@ static ulong ast2500_configure_d2pll(struct ast2500_scu
*scu, ulong rate)
/*
* The values and the meaning of the next three
* parameters are undocumented. Taken from Aspeed SDK.
+ *
+ * TODO(c...@kaod.org): the SIP and SIC values depend on the
+ * Numerator value
*/
const u32 d2_pll_ext_param = 0x2c;
const u32 d2_pll_sip = 0x11;
--
2.17.1
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