Re: [PATCH][next] soc: xilinx: vcu: remove deadcode on null divider check
On Thu, 18 Mar 2021 12:48:06 +, 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 > > 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 > --- > 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.tret...@pengutronix.de 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.tret...@pengutronix.de Michael
Re: [PATCH][next] soc: xilinx: vcu: remove deadcode on null divider check
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 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 --- 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.tret...@pengutronix.de 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); + if (!mux) return; - clk_hw_unregister_divider(divider); + clk_hw_unregister_divider(mux);
Re: [PATCH][next] soc: xilinx: vcu: remove deadcode on null divider check
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 > > > > > > 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 > > > --- > > > 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.tret...@pengutronix.de 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. >
Re: [PATCH][next] soc: xilinx: vcu: remove deadcode on null divider check
On 11/02/2021 07:31, Michael Tretter wrote: > On Wed, 10 Feb 2021 18:49:38 +, Colin King wrote: >> From: Colin Ian King >> >> 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 >> --- >> 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; >> - >> clk_hw_unregister_divider(divider); > > Thanks for pointing this out. There is actually a different bug there. > > There should have been a check for !mux before unregistering the mux: > > mux = clk_hw_get_parent(divider); > clk_hw_unregister_divider(divider); > if (!mux) > return; Ah, that makes sense, I'll send a V2. > > clk_hw_unregister_mux(mux); > > Michael > >> } >> >> -- >> 2.30.0 >> >>
Re: [PATCH][next] soc: xilinx: vcu: remove deadcode on null divider check
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 > > > > 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 > > --- > > 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.tret...@pengutronix.de to > reply Can you elaborate what you find confusing about this code. I would gladly try to clarify and improve the code. 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. Michael > > > clk_hw_unregister_divider(divider); > > } > > >
Re: [PATCH][next] soc: xilinx: vcu: remove deadcode on null divider check
On Wed, 10 Feb 2021 18:49:38 +, Colin King wrote: > From: Colin Ian King > > 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 > --- > 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; > - > clk_hw_unregister_divider(divider); Thanks for pointing this out. There is actually a different bug there. There should have been a check for !mux before unregistering the mux: mux = clk_hw_get_parent(divider); clk_hw_unregister_divider(divider); if (!mux) return; clk_hw_unregister_mux(mux); Michael > } > > -- > 2.30.0 > >
Re: [PATCH][next] soc: xilinx: vcu: remove deadcode on null divider check
Quoting Colin King (2021-02-10 10:49:38) > From: Colin Ian King > > 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 > --- > 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.tret...@pengutronix.de to reply > clk_hw_unregister_divider(divider); > } >
[PATCH][next] soc: xilinx: vcu: remove deadcode on null divider check
From: Colin Ian King 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 --- 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; - clk_hw_unregister_divider(divider); } -- 2.30.0