Re: [PATCH] clk: imx25: set correct parents for ssi ipg clocks

[Martin Kaiser <martin@kaiser.cx>]

Hi Fabio & Lothar,

Thus wrote Fabio Estevam (festevam@gmail.com):

> On Thu, Mar 8, 2018 at 1:46 PM, Martin Kaiser <martin@kaiser.cx> wrote:

> >> I can get audio to work fine without your patch on a mx25pdk.

> > this is surprising. How come the ssi1_ipg_per clock is not turned off by
> > clk_disable_unused()? Where is it used? Do you have

> > <&clks 55>

> > anywhere in your DT?

> No, I don't. imx25-pdk board operates SSI in slave mode.

> > (My codec chip does not use a dedicated clock line. It takes the bit clock that
> > is the output of SSI. Are you maybe using ssi1_ipg_per for your codec and
> > enable it there?)

> The difference between our boards is that you use SSI in master mode
> and mx25pdk in slave mode.

> > In my first mail, I was wondering about imx25 uart1, where we also have
> > uart1_ipg and uart_ipg_per and the clock seeting is

> >    clk[uart1_ipg] = imx_clk_gate("uart1_ipg", "ipg", ccm(CCM_CGCR2), 14);

> > In this case, both uart1 and uart_ipg_per are listed in the device tree

> >          uart1: serial@43f90000 {
> > ...
> >             clocks = <&clks 120>, <&clks 57>;
> >             clock-names = "ipg", "per";
> >          };

> > Documentation/devicetree/bindings/clock/imx25-clock.txt
> >    uart_ipg_per      57
> >    uart1_ipg      120

> > and the driver enables both clocks explicitly. So they are not unused.


> > Doing something like this is not an option for ssi, this will not work with
> > imx31, 35 etc.

> The solution to this is passing the "baud" clock as Lothar pointed out.

ok, I got your point now.

The ssi1_ipg clock does not depend on ssi1_ipg_per. This is in line with
the clock generation scheme in the reference manual.

And there's configurations where ssi1_ipg should be switched on, but not
ssi1_ipg_per.

I'll look into using the baud clock on my board.

Thanks to both of you for taking the time to explain this.

Best regards,

   Martin