On Thu, 18 Mar 2021 12:48:06 +0000, Colin Ian King wrote:
> On 11/02/2021 19:05, Stephen Boyd wrote:
> > Quoting Michael Tretter (2021-02-10 23:39:06)
> >> On Wed, 10 Feb 2021 19:28:18 -0800, Stephen Boyd wrote:
> >>> Quoting Colin King (2021-02-10 10:49:38)
> >>>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> >>>>
> >>>> The pointer 'divider' has previously been null checked followed by
> >>>> a return, hence the subsequent null check is redundant deadcode
> >>>> that can be removed. Clean up the code and remove it.
> >>>>
> >>>> Fixes: 9c789deea206 ("soc: xilinx: vcu: implement clock provider for output clocks")
> >>>> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> >>>> ---
> >>>> drivers/clk/xilinx/xlnx_vcu.c | 3 ---
> >>>> 1 file changed, 3 deletions(-)
> >>>>
> >>>> diff --git a/drivers/clk/xilinx/xlnx_vcu.c b/drivers/clk/xilinx/xlnx_vcu.c
> >>>> index d66b1315114e..607936d7a413 100644
> >>>> --- a/drivers/clk/xilinx/xlnx_vcu.c
> >>>> +++ b/drivers/clk/xilinx/xlnx_vcu.c
> >>>> @@ -512,9 +512,6 @@ static void xvcu_clk_hw_unregister_leaf(struct clk_hw *hw)
> >>>>
> >>>> mux = clk_hw_get_parent(divider);
> >>>> clk_hw_unregister_mux(mux);
> >>>> - if (!divider)
> >>>> - return;
> >>>> -
> >>>
> >>> This code is pretty confusing. Waiting for m.tretter@xxxxxxxxxxxxxx to
> >>> reply
> >>
> >> Can you elaborate what you find confusing about this code. I would gladly try
> >> to clarify and improve the code.
> >
> > The fact that pointers are being checked and then bailing out of the
> > function early, vs. doing something if the pointer is non-NULL.
> >
> >>
> >> What happens here is that the driver registers a mux -> divider -> gate chain
> >> for each output clock, but only stores the gate clock. When unregistering the
> >> clocks, the driver starts at the gate and walks up to the mux while
> >> unregistering the clocks.
> >>
>
> OK, so I think I understand this better, should the order of
> unregisteration be as follows:
>
> diff --git a/drivers/clk/xilinx/xlnx_vcu.c b/drivers/clk/xilinx/xlnx_vcu.c
> index d66b1315114e..66bac8421460 100644
> --- a/drivers/clk/xilinx/xlnx_vcu.c
> +++ b/drivers/clk/xilinx/xlnx_vcu.c
> @@ -511,11 +511,11 @@ static void xvcu_clk_hw_unregister_leaf(struct
> clk_hw *hw)
> return;
>
> mux = clk_hw_get_parent(divider);
> - clk_hw_unregister_mux(mux);
> - if (!divider)
> + clk_hw_unregister_mux(divider);
The order is correct, but this must be:
clk_hw_unregister_divider(divider);
> + if (!mux)
> return;
>
> - clk_hw_unregister_divider(divider);
> + clk_hw_unregister_divider(mux);
>
clk_hw_unregister_mux(mux);
Taking the confusion expressed by Stephen into account, I rewrote the entire
function to clarify what is happening in this function. Please take a look
that patch [0] and tell me, if it is now easier to understand.
[0] 20210318144230.3438009-1-m.tretter@xxxxxxxxxxxxxx
Michael
