Re: [PATCH v13 2/4] clk: scmi: reject SSC configuration out of the OEM field range

[Peng Fan <peng.fan@oss.nxp.com>]

On Thu, Sep 03, 2026 at 05:32:14PM +0200, Dario Binacchi wrote:
>The i.MX SCMI OEM extension stores the spread in an 8-bit field, in
>tenths of a percent, and the modulation frequency in a 16-bit field.
>
>FIELD_PREP() silently truncates values that do not fit in the target
>field. Moreover, the conversion from permyriad to tenths of a percent
>turns values below 10 permyriad into zero, which is then passed to the
>firmware as no spread at all.
>
>Reject these cases with a warning instead of silently programming a
>configuration different from the requested one.
>
>Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
>
>---
>
>Changes in v13:
> - New patch
>
> drivers/clk/clk-scmi-oem.c | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/clk/clk-scmi-oem.c b/drivers/clk/clk-scmi-oem.c
>index c1ebbdc6bbc5..4dac608edd4c 100644
>--- a/drivers/clk/clk-scmi-oem.c
>+++ b/drivers/clk/clk-scmi-oem.c
>@@ -35,6 +35,7 @@ scmi_clk_imx_set_spread_spectrum(struct clk_hw *hw,
> 				 const struct clk_spread_spectrum *ss_conf)
> {
> 	struct scmi_clk *clk = to_scmi_clk(hw);
>+	u32 spread_pm = ss_conf->spread_bp / 10;
> 	int ret;
> 	u32 val;
> 
>@@ -44,7 +45,19 @@ scmi_clk_imx_set_spread_spectrum(struct clk_hw *hw,
> 	 * extConfigValue[24]    - Enable/Disable
> 	 * extConfigValue[31:25] - Reserved
> 	 */
>-	val = FIELD_PREP(SCMI_CLOCK_IMX_SS_PERCENTAGE_MASK, ss_conf->spread_bp / 10);
>+	if (!spread_pm || spread_pm > FIELD_MAX(SCMI_CLOCK_IMX_SS_PERCENTAGE_MASK)) {
>+		dev_warn(clk->dev, "%s: spread (%u permyriad) out of range\n",
>+			 clk_hw_get_name(hw), ss_conf->spread_bp);
>+		return -EINVAL;

sashiko's comments is valid.

And patch 1 & 3 have fixes tag. Patch 2 and 4 are new patches.
If you would like patch 1 & 3 to be accepted in this 7.13, better post them
as separate patchset. Then CLK maintainer may pick them up for this release.

Regards
Peng

>+	}
>+
>+	if (ss_conf->modfreq_hz > FIELD_MAX(SCMI_CLOCK_IMX_SS_MOD_FREQ_MASK)) {
>+		dev_warn(clk->dev, "%s: modulation frequency (%u Hz) out of range\n",
>+			 clk_hw_get_name(hw), ss_conf->modfreq_hz);
>+		return -EINVAL;
>+	}
>+
>+	val = FIELD_PREP(SCMI_CLOCK_IMX_SS_PERCENTAGE_MASK, spread_pm);
> 	val |= FIELD_PREP(SCMI_CLOCK_IMX_SS_MOD_FREQ_MASK, ss_conf->modfreq_hz);
> 	if (ss_conf->method != CLK_SPREAD_NO)
> 		val |= SCMI_CLOCK_IMX_SS_ENABLE_MASK;
>-- 
>2.43.0
>
>