Hi Maxime,
On 4/25/23 09:48, Maxime Ripard wrote:
Hi Dinh,
On Mon, Apr 24, 2023 at 01:32:28PM -0500, Dinh Nguyen wrote:
On 4/4/23 05:11, Maxime Ripard wrote:
The SoCFGPA gate clock implements a mux with a set_parent hook, but
doesn't provide a determine_rate implementation.
This is a bit odd, since set_parent() is there to, as its name implies,
change the parent of a clock. However, the most likely candidate to
trigger that parent change is a call to clk_set_rate(), with
determine_rate() figuring out which parent is the best suited for a
given rate.
The other trigger would be a call to clk_set_parent(), but it's far less
used, and it doesn't look like there's any obvious user for that clock.
So, the set_parent hook is effectively unused, possibly because of an
oversight. However, it could also be an explicit decision by the
original author to avoid any reparenting but through an explicit call to
clk_set_parent().
The latter case would be equivalent to setting the flag
CLK_SET_RATE_NO_REPARENT, together with setting our determine_rate hook
to __clk_mux_determine_rate(). Indeed, if no determine_rate
implementation is provided, clk_round_rate() (through
clk_core_round_rate_nolock()) will call itself on the parent if
CLK_SET_RATE_PARENT is set, and will not change the clock rate
otherwise. __clk_mux_determine_rate() has the exact same behavior when
CLK_SET_RATE_NO_REPARENT is set.
And if it was an oversight, then we are at least explicit about our
behavior now and it can be further refined down the line.
Signed-off-by: Maxime Ripard <maxime@xxxxxxxxxx>
---
drivers/clk/socfpga/clk-gate.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/clk/socfpga/clk-gate.c b/drivers/clk/socfpga/clk-gate.c
index 32ccda960f28..cbba8462a09e 100644
--- a/drivers/clk/socfpga/clk-gate.c
+++ b/drivers/clk/socfpga/clk-gate.c
@@ -110,6 +110,7 @@ static unsigned long socfpga_clk_recalc_rate(struct clk_hw *hwclk,
static struct clk_ops gateclk_ops = {
.recalc_rate = socfpga_clk_recalc_rate,
+ .determine_rate = __clk_mux_determine_rate,
.get_parent = socfpga_clk_get_parent,
.set_parent = socfpga_clk_set_parent,
};
@@ -166,7 +167,7 @@ void __init socfpga_gate_init(struct device_node *node)
init.name = clk_name;
init.ops = ops;
- init.flags = 0;
+ init.flags = CLK_SET_RATE_NO_REPARENT;
init.num_parents = of_clk_parent_fill(node, parent_name, SOCFPGA_MAX_PARENTS);
if (init.num_parents < 2) {
This patch broke SoCFPGA boot serial port. The characters are mangled.
Do you have any other access to that board? If so, could you dump
clk_summary in debugfs with and without that patch?
That dump from the clk_summary are identical for both cases.
