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

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Date:   Fri, 9 Mar 2018 23:37:33 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     Martin Kaiser <martin@...ser.cx>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        Fabio Estevam <fabio.estevam@....com>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] clk: imx25: set correct parents for ssi ipg clocks

Hi Martin,

On Thu, Mar 8, 2018 at 1:46 PM, Martin Kaiser <martin@...ser.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@...90000 {
> ...
>             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.