From: Brian Masney bmasney@redhat.com
[ Upstream commit 80cb2b6edd8368f7e1e8bf2f66aabf57aa7de4b7 ]
This driver implements both the determine_rate() and round_rate() clk ops, and the round_rate() clk ops is deprecated. When both are defined, clk_core_determine_round_nolock() from the clk core will only use the determine_rate() clk ops.
The existing scmi_clk_determine_rate() is a noop implementation that lets the firmware round the rate as appropriate. Drop the existing determine_rate implementation and convert the existing round_rate() implementation over to determine_rate().
scmi_clk_determine_rate() was added recently when the clock parent support was added, so it's not expected that this change will regress anything.
Reviewed-by: Sudeep Holla sudeep.holla@arm.com Reviewed-by: Peng Fan peng.fan@nxp.com Tested-by: Peng Fan peng.fan@nxp.com #i.MX95-19x19-EVK Signed-off-by: Brian Masney bmasney@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org ---
LLM Generated explanations, may be completely bogus:
YES The patch restores the SCMI clock driver's ability to return a valid rounded rate when the framework asks for it.
- With the regression-introducing stub in `scmi_clk_determine_rate()` every request fell through without touching `req->rate`, so `clk_core_determine_round_nolock()` would return the caller’s original value whenever both ops were present (`drivers/clk/clk.c:1596-1613`), making `clk_round_rate()` lie about the hardware outcome on platforms that advertise min/max/step limits. - The new implementation in `drivers/clk/clk-scmi.c:57-90` moves the logic that used to live in `.round_rate()` into `.determine_rate()`, clamping to `min_rate`/`max_rate` and quantising by `step_size`, exactly reproducing the behaviour that worked before the noop `determine_rate()` was introduced. - Discrete-rate clocks remain unchanged—the function still bails out early (`drivers/clk/clk-scmi.c:63-71`), matching the old behaviour—and the ops table simply stops advertising the deprecated `.round_rate()` callback (`drivers/clk/clk-scmi.c:299-304`), so risk is minimal and confined to SCMI clocks. - The bug has shipped since the recent parent-support work (first seen in v6.10), so stable kernels carrying that change are returning incorrect values to consumers today.
Because this is a regression fix with low risk and no architectural churn, it is a good candidate for backporting to every stable series that contains the broken noop `determine_rate()`.
drivers/clk/clk-scmi.c | 35 ++++++++++++++++------------------- 1 file changed, 16 insertions(+), 19 deletions(-)
diff --git a/drivers/clk/clk-scmi.c b/drivers/clk/clk-scmi.c index d2408403283fc..78dd2d9c7cabd 100644 --- a/drivers/clk/clk-scmi.c +++ b/drivers/clk/clk-scmi.c @@ -54,8 +54,8 @@ static unsigned long scmi_clk_recalc_rate(struct clk_hw *hw, return rate; }
-static long scmi_clk_round_rate(struct clk_hw *hw, unsigned long rate, - unsigned long *parent_rate) +static int scmi_clk_determine_rate(struct clk_hw *hw, + struct clk_rate_request *req) { u64 fmin, fmax, ftmp; struct scmi_clk *clk = to_scmi_clk(hw); @@ -67,20 +67,27 @@ static long scmi_clk_round_rate(struct clk_hw *hw, unsigned long rate, * running at then. */ if (clk->info->rate_discrete) - return rate; + return 0;
fmin = clk->info->range.min_rate; fmax = clk->info->range.max_rate; - if (rate <= fmin) - return fmin; - else if (rate >= fmax) - return fmax; + if (req->rate <= fmin) { + req->rate = fmin; + + return 0; + } else if (req->rate >= fmax) { + req->rate = fmax;
- ftmp = rate - fmin; + return 0; + } + + ftmp = req->rate - fmin; ftmp += clk->info->range.step_size - 1; /* to round up */ do_div(ftmp, clk->info->range.step_size);
- return ftmp * clk->info->range.step_size + fmin; + req->rate = ftmp * clk->info->range.step_size + fmin; + + return 0; }
static int scmi_clk_set_rate(struct clk_hw *hw, unsigned long rate, @@ -119,15 +126,6 @@ static u8 scmi_clk_get_parent(struct clk_hw *hw) return p_idx; }
-static int scmi_clk_determine_rate(struct clk_hw *hw, struct clk_rate_request *req) -{ - /* - * Suppose all the requested rates are supported, and let firmware - * to handle the left work. - */ - return 0; -} - static int scmi_clk_enable(struct clk_hw *hw) { struct scmi_clk *clk = to_scmi_clk(hw); @@ -300,7 +298,6 @@ scmi_clk_ops_alloc(struct device *dev, unsigned long feats_key)
/* Rate ops */ ops->recalc_rate = scmi_clk_recalc_rate; - ops->round_rate = scmi_clk_round_rate; ops->determine_rate = scmi_clk_determine_rate; if (feats_key & BIT(SCMI_CLK_RATE_CTRL_SUPPORTED)) ops->set_rate = scmi_clk_set_rate;