2023-03-31 07:22:20

by Peng Fan (OSS)

Subject: [PATCH] clk: imx: imx6sx: spdif clock rate is too high for asrc

From: Shengjiu Wang <[email protected]>

spdif clock is one of the asrc clock source, which is used
for ideal ratio mode. when set to 98.304MHz, it cause the
divider of asrc input clock and output clock exceed the
maximum value, and asrc driver saturate the value to maximum
value, which will cause the ASRC's performance very bad.
So we need to set spdif clock to a proper rate. which make asrc
divider not exceed maximum value, at least one of divider not
exceed maximum value.
The target is spdif clock rate / output(or input) sample rate
less than 1024(which is maximum divider).

Signed-off-by: Shengjiu Wang <[email protected]>
Signed-off-by: Peng Fan <[email protected]>
---
drivers/clk/imx/clk-imx6sx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/imx/clk-imx6sx.c b/drivers/clk/imx/clk-imx6sx.c
index 7cf86707bc39..3face052527d 100644
--- a/drivers/clk/imx/clk-imx6sx.c
+++ b/drivers/clk/imx/clk-imx6sx.c
@@ -520,7 +520,7 @@ static void __init imx6sx_clocks_init(struct device_node *ccm_node)
clk_set_rate(hws[IMX6SX_CLK_PLL4_AUDIO_DIV]->clk, 393216000);

clk_set_parent(hws[IMX6SX_CLK_SPDIF_SEL]->clk, hws[IMX6SX_CLK_PLL4_AUDIO_DIV]->clk);
- clk_set_rate(hws[IMX6SX_CLK_SPDIF_PODF]->clk, 98304000);
+ clk_set_rate(hws[IMX6SX_CLK_SPDIF_PODF]->clk, 24576000);

clk_set_parent(hws[IMX6SX_CLK_AUDIO_SEL]->clk, hws[IMX6SX_CLK_PLL3_USB_OTG]->clk);
clk_set_rate(hws[IMX6SX_CLK_AUDIO_PODF]->clk, 24000000);
--
2.37.1

2023-03-31 10:38:24

by Fabio Estevam

Subject: Re: [PATCH] clk: imx: imx6sx: spdif clock rate is too high for asrc

On Fri, Mar 31, 2023 at 4:15 AM Peng Fan (OSS) <[email protected]> wrote:
>
> From: Shengjiu Wang <[email protected]>
>
> spdif clock is one of the asrc clock source, which is used
> for ideal ratio mode. when set to 98.304MHz, it cause the
> divider of asrc input clock and output clock exceed the
> maximum value, and asrc driver saturate the value to maximum
> value, which will cause the ASRC's performance very bad.
> So we need to set spdif clock to a proper rate. which make asrc
> divider not exceed maximum value, at least one of divider not
> exceed maximum value.
> The target is spdif clock rate / output(or input) sample rate
> less than 1024(which is maximum divider).

Please add a Fixes tag.