Hi Greg,
On 17.09.23 21:13, Greg Kroah-Hartman wrote:
5.15-stable review patch. If anyone has any objections, please let me know.
From: Ahmad Fatoum a.fatoum@pengutronix.de
commit 72d00e560d10665e6139c9431956a87ded6e9880 upstream.
Since commit b09c68dc57c9 ("clk: imx: pll14xx: Support dynamic rates"), the driver has the ability to dynamically compute PLL parameters to approximate the requested rates. This is not always used, because the logic is as follows:
- Check if the target rate is hardcoded in the frequency table
- Check if varying only kdiv is possible, so switch over is glitch free
- Compute rate dynamically by iterating over pdiv range
If we skip the frequency table for the 1443x PLL, we find that the computed values differ to the hardcoded ones. This can be valid if the hardcoded values guarantee for example an earlier lock-in or if the divisors are chosen, so that other important rates are more likely to be reached glitch-free.
For rates (393216000 and 361267200, this doesn't seem to be the case: They are only approximated by existing parameters (393215995 and 361267196 Hz, respectively) and they aren't reachable glitch-free from other hardcoded frequencies. Dropping them from the table allows us to lock-in to these frequencies exactly.
This is immediately noticeable because they are the assigned-clock-rates for IMX8MN_AUDIO_PLL1 and IMX8MN_AUDIO_PLL2, respectively and a look into clk_summary so far showed that they were a few Hz short of the target:
imx8mn-board:~# grep audio_pll[12]_out /sys/kernel/debug/clk/clk_summary audio_pll2_out 0 0 0 361267196 0 0 50000 N audio_pll1_out 1 1 0 393215995 0 0 50000 Y
and afterwards:
imx8mn-board:~# grep audio_pll[12]_out /sys/kernel/debug/clk/clk_summary audio_pll2_out 0 0 0 361267200 0 0 50000 N audio_pll1_out 1 1 0 393216000 0 0 50000 Y
This change is equivalent to adding following hardcoded values:
/* rate mdiv pdiv sdiv kdiv */ PLL_1443X_RATE(393216000, 655, 5, 3, 23593), PLL_1443X_RATE(361267200, 497, 33, 0, -16882),
Fixes: 053a4ffe2988 ("clk: imx: imx8mm: fix audio pll setting") Cc: stable@vger.kernel.org # v5.18+
Patch is only correct for v5.18 onward. Please drop for v5.15.
Is there another syntax that we should've used instead that your tools pick up?
Thanks, Ahmad
Signed-off-by: Ahmad Fatoum a.fatoum@pengutronix.de Signed-off-by: Marco Felsch m.felsch@pengutronix.de Link: https://lore.kernel.org/r/20230807084744.1184791-2-m.felsch@pengutronix.de Signed-off-by: Abel Vesa abel.vesa@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
drivers/clk/imx/clk-pll14xx.c | 2 -- 1 file changed, 2 deletions(-)
--- a/drivers/clk/imx/clk-pll14xx.c +++ b/drivers/clk/imx/clk-pll14xx.c @@ -60,8 +60,6 @@ static const struct imx_pll14xx_rate_tab PLL_1443X_RATE(650000000U, 325, 3, 2, 0), PLL_1443X_RATE(594000000U, 198, 2, 2, 0), PLL_1443X_RATE(519750000U, 173, 2, 2, 16384),
- PLL_1443X_RATE(393216000U, 262, 2, 3, 9437),
- PLL_1443X_RATE(361267200U, 361, 3, 3, 17511),
}; struct imx_pll14xx_clk imx_1443x_pll = {