[PATCH] clock_imx8mq: Added 66 MHz support for QSPI

[Fabio Estevam]

Hi Kwon,

On Wed, Jun 23, 2021 at 10:13 PM Kwon Tae-young <tykwon at m2i.co.kr> wrote:
>
> At the current clock setting, the maximum clock for QSPI is 25 MHz.
> In my case I use M-RAM which supports up to 100 MHz for QSPI, and with
> this change the QSPI can be clocked up to 66 MHz.
>
> Signed-off-by: Kwon Tae-young <tykwon at m2i.co.kr>
> ---
>  arch/arm/mach-imx/imx8m/clock_imx8mq.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/mach-imx/imx8m/clock_imx8mq.c b/arch/arm/mach-imx/imx8m/clock_imx8mq.c
> index 8fecc60ecb..47b4a8f01f 100644
> --- a/arch/arm/mach-imx/imx8m/clock_imx8mq.c
> +++ b/arch/arm/mach-imx/imx8m/clock_imx8mq.c
> @@ -473,11 +473,11 @@ int set_clk_qspi(void)
>  {
>         /*
>          * set qspi root
> -        * sys pll1 100M
> +        * sys pll1 266M
>          */
>         clock_enable(CCGR_QSPI, 0);
>         clock_set_target_val(QSPI_CLK_ROOT, CLK_ROOT_ON |
> -                            CLK_ROOT_SOURCE_SEL(7));
> +                            CLK_ROOT_SOURCE_SEL(5));

It seems there is 'divide-by 4' being set somewhere.

What if you use CLK_ROOT_SOURCE_SEL(1) instead?

This selects SYS_PLL1_400MHz as the QSPI parent clock and should give
you the 100MHz QSPI clock
that you need.