On Fri, Jun 24, 2022 at 6:52 AM Francesco Dolcini francesco.dolcini@toradex.com wrote:
Set CLK01 and CLK02 to 24MHz and enable it in CCM_CCOSR register.
This clock is used by both the audio codec (CLKO1) and by the CSI camera (CLKO2) and is expected to be 24MHz.
Despite the wrong 16.5MHz there was no real issue because of the wrong frequency since Linux reconfigures the clocks afterward, however this was triggering an issue with noise coming from the SGTL5000 audio codec.
The problem is that the SGTL5000 does not have a reset pin and after it is configured if the input MCLK clock is disabled it produces a constant noise on its output, this was happening on software reboot.
Forcing the clock to be enabled in U-Boot prevent the problem by making sure that the clock is always available, without this change as soon as Linux was changing the clock tree (setting clk_out_sel=1 without setting clko2_en=1) the noise would start till the actual clock was enabled (clko2_en=1) during the SGTL5000 driver probe.
Signed-off-by: Francesco Dolcini francesco.dolcini@toradex.com
Reviewed-by: Fabio Estevam festevam@denx.de