[PATCH v4 0/2] mark spi clocks as critical and enable spi3 clocks

[PATCH v4 0/2] mark spi clocks as critical and enable spi3 clocks

[Andi Shyti]

Hi,

I managed to bring some confusion on these two patches, but
finally I managed to find the right solution (which is similar to
the patch version 2).

The real issue was hidden in the spi bus as reported in the
following patch:

  https://lkml.org/lkml/2016/7/7/81

This patch in principle replaces the clock_ignore_unused flags in
for the spi and enables the spi3 that in the tm2(e) board will be
connected to the IR remote controller.

Changelog:

V1 -> V2
 - the "sclk_spi3" doesn't need to be enabled in boot time as it
  is handled by the spi driver itself.

 - use the CLK_IS_CRITICAL flag for the ioclk

V2 -> V3
 - some more tests has confirmed taht "sclk_spi1,3" need to be
   enabled as critical!

 - added Chanwoo's review in the second commit.

V3 -> V4
 - patch V3 was wrong, back to patch v2.

 - reworded the commit of patch no. 1

Thanks,
Andi

Andi Shyti (2):
  clk: exynos5433: do not use CLK_IGNORE_UNUSED for SPI clocks
  clk: exynos5433: enable sclk_ioclk for SPI3

 drivers/clk/samsung/clk-exynos5433.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

-- 
2.8.1

[PATCH v4 1/2] clk: exynos5433: do not use CLK_IGNORE_UNUSED for SPI clocks

[Andi Shyti]

The CLK_IGNORE_UNUSED flag has to be avoided whenever possible.
Use the CLK_IS_CRITICAL flag instead for critical SPI1 clocks,
which enables the clock line during boot time.

Suggested-by: Tomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
---
 drivers/clk/samsung/clk-exynos5433.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/samsung/clk-exynos5433.c b/drivers/clk/samsung/clk-exynos5433.c
index c3a5318..337387b 100644
--- a/drivers/clk/samsung/clk-exynos5433.c
+++ b/drivers/clk/samsung/clk-exynos5433.c
@@ -1662,7 +1662,7 @@ static struct samsung_gate_clock peric_gate_clks[] __initdata = {
 			ENABLE_SCLK_PERIC, 13, CLK_SET_RATE_PARENT, 0),
 	GATE(CLK_SCLK_IOCLK_SPI1, "sclk_ioclk_spi1", "ioclk_spi1_clk_in",
 			ENABLE_SCLK_PERIC, 12,
-			CLK_IGNORE_UNUSED | CLK_SET_RATE_PARENT, 0),
+			CLK_IS_CRITICAL | CLK_SET_RATE_PARENT, 0),
 	GATE(CLK_SCLK_IOCLK_SPI0, "sclk_ioclk_spi0", "ioclk_spi0_clk_in",
 			ENABLE_SCLK_PERIC, 11, CLK_SET_RATE_PARENT, 0),
 	GATE(CLK_SCLK_IOCLK_I2S1_BCLK, "sclk_ioclk_i2s1_bclk",
@@ -1677,7 +1677,7 @@ static struct samsung_gate_clock peric_gate_clks[] __initdata = {
 	GATE(CLK_SCLK_SPI2, "sclk_spi2", "sclk_spi2_peric", ENABLE_SCLK_PERIC,
 			5, CLK_SET_RATE_PARENT, 0),
 	GATE(CLK_SCLK_SPI1, "sclk_spi1", "sclk_spi1_peric", ENABLE_SCLK_PERIC,
-			4, CLK_IGNORE_UNUSED | CLK_SET_RATE_PARENT, 0),
+			4, CLK_SET_RATE_PARENT, 0),
 	GATE(CLK_SCLK_SPI0, "sclk_spi0", "sclk_spi0_peric", ENABLE_SCLK_PERIC,
 			3, CLK_SET_RATE_PARENT, 0),
 	GATE(CLK_SCLK_UART2, "sclk_uart2", "sclk_uart2_peric",
-- 
2.8.1

Re: [PATCH v4 1/2] clk: exynos5433: do not use CLK_IGNORE_UNUSED for SPI clocks

[Krzysztof Kozlowski]

On 07/07/2016 02:13 PM, Andi Shyti wrote:
> The CLK_IGNORE_UNUSED flag has to be avoided whenever possible.
> Use the CLK_IS_CRITICAL flag instead for critical SPI1 clocks,
> which enables the clock line during boot time.

I don't agree. Both flags should be avoided. Clk is critical does not
solve the problem. It is just a better workaround for lack of proper
clock consumers.

The IOCLK is not a critical clock. It can be disabled (e.g. when SoC is
used on a board without any SPI device connected).

Best regards,
Krzysztof

> 
> Suggested-by: Tomasz Figa <tomasz.figa@gmail.com>
> Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
> ---
>  drivers/clk/samsung/clk-exynos5433.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clk/samsung/clk-exynos5433.c b/drivers/clk/samsung/clk-exynos5433.c
> index c3a5318..337387b 100644
> --- a/drivers/clk/samsung/clk-exynos5433.c
> +++ b/drivers/clk/samsung/clk-exynos5433.c
> @@ -1662,7 +1662,7 @@ static struct samsung_gate_clock peric_gate_clks[] __initdata = {
>  			ENABLE_SCLK_PERIC, 13, CLK_SET_RATE_PARENT, 0),
>  	GATE(CLK_SCLK_IOCLK_SPI1, "sclk_ioclk_spi1", "ioclk_spi1_clk_in",
>  			ENABLE_SCLK_PERIC, 12,
> -			CLK_IGNORE_UNUSED | CLK_SET_RATE_PARENT, 0),
> +			CLK_IS_CRITICAL | CLK_SET_RATE_PARENT, 0),
>  	GATE(CLK_SCLK_IOCLK_SPI0, "sclk_ioclk_spi0", "ioclk_spi0_clk_in",
>  			ENABLE_SCLK_PERIC, 11, CLK_SET_RATE_PARENT, 0),
>  	GATE(CLK_SCLK_IOCLK_I2S1_BCLK, "sclk_ioclk_i2s1_bclk",
> @@ -1677,7 +1677,7 @@ static struct samsung_gate_clock peric_gate_clks[] __initdata = {
>  	GATE(CLK_SCLK_SPI2, "sclk_spi2", "sclk_spi2_peric", ENABLE_SCLK_PERIC,
>  			5, CLK_SET_RATE_PARENT, 0),
>  	GATE(CLK_SCLK_SPI1, "sclk_spi1", "sclk_spi1_peric", ENABLE_SCLK_PERIC,
> -			4, CLK_IGNORE_UNUSED | CLK_SET_RATE_PARENT, 0),
> +			4, CLK_SET_RATE_PARENT, 0),
>  	GATE(CLK_SCLK_SPI0, "sclk_spi0", "sclk_spi0_peric", ENABLE_SCLK_PERIC,
>  			3, CLK_SET_RATE_PARENT, 0),
>  	GATE(CLK_SCLK_UART2, "sclk_uart2", "sclk_uart2_peric",
> 

Re: [PATCH v4 1/2] clk: exynos5433: do not use CLK_IGNORE_UNUSED for SPI clocks

[Andi Shyti]

Hi Krzysztof,

> > The CLK_IGNORE_UNUSED flag has to be avoided whenever possible.
> > Use the CLK_IS_CRITICAL flag instead for critical SPI1 clocks,
> > which enables the clock line during boot time.
> 
> I don't agree. Both flags should be avoided. Clk is critical does not
> solve the problem. It is just a better workaround for lack of proper
> clock consumers.
> 
> The IOCLK is not a critical clock. It can be disabled (e.g. when SoC is
> used on a board without any SPI device connected).

As we discussed offline there is no driver which is requesting
this clock. We cannot ask to the spi driver to handle three
clocks because the exynos5433 has its own peculiarities.

If we want this on the spi driver's side, we need to add a new
compatible and check it everytime. To me it looks uglier than
just keep it alive.

Thanks,
Andi

Re: [PATCH v4 1/2] clk: exynos5433: do not use CLK_IGNORE_UNUSED for SPI clocks

[Sylwester Nawrocki]

On 07/07/2016 03:27 PM, Andi Shyti wrote:
>>> > > The CLK_IGNORE_UNUSED flag has to be avoided whenever possible.
>>> > > Use the CLK_IS_CRITICAL flag instead for critical SPI1 clocks,
>>> > > which enables the clock line during boot time.
>> > 
>> > I don't agree. Both flags should be avoided. Clk is critical does not
>> > solve the problem. It is just a better workaround for lack of proper
>> > clock consumers.
>> > 
>> > The IOCLK is not a critical clock. It can be disabled (e.g. when SoC
>> >  is used on a board without any SPI device connected).
>
> As we discussed offline there is no driver which is requesting
> this clock. We cannot ask to the spi driver to handle three
> clocks because the exynos5433 has its own peculiarities.
> 
> If we want this on the spi driver's side, we need to add a new
> compatible and check it everytime. To me it looks uglier than
> just keep it alive.

I took a closer look at what those IOCLK clocks exactly are and
unfortunately I must agree with Krzysztof.  These clock gates are
closely related to the IP blocks and to me proper approach is to
have them listed in DT and controlled by the SPI bus driver.

I checked and there is similar pattern for other IPs like I2S and
other SoCs, e.g. exynos7420.
Additionally parents of those IOCLK_SPI?_CLK clocks are currently
wrongly modelled as fixed rate clocks.  These clocks really don't
have a parent until some clock is fed externally to the SoC's I/O
pin.  But this issue could be addressed later.

I think it is not a big deal to add "samsung-exynos5433-spi"
compatible to the SPI driver along with a new variant data and
a flag like "has_cmu_ioclk" to indicate whether a third clock
should be handled or not. Presumably for now the ioclk clock can
just simply be enabled in probe(), this way it will be enabled
only for SPI controllers actually in use.

Re: [PATCH v4 1/2] clk: exynos5433: do not use CLK_IGNORE_UNUSED for SPI clocks

[Andi Shyti]

Hi Sylwester,

> >>> > > The CLK_IGNORE_UNUSED flag has to be avoided whenever possible.
> >>> > > Use the CLK_IS_CRITICAL flag instead for critical SPI1 clocks,
> >>> > > which enables the clock line during boot time.
> >> > 
> >> > I don't agree. Both flags should be avoided. Clk is critical does not
> >> > solve the problem. It is just a better workaround for lack of proper
> >> > clock consumers.
> >> > 
> >> > The IOCLK is not a critical clock. It can be disabled (e.g. when SoC
> >> >  is used on a board without any SPI device connected).
> >
> > As we discussed offline there is no driver which is requesting
> > this clock. We cannot ask to the spi driver to handle three
> > clocks because the exynos5433 has its own peculiarities.
> > 
> > If we want this on the spi driver's side, we need to add a new
> > compatible and check it everytime. To me it looks uglier than
> > just keep it alive.
> 
> I took a closer look at what those IOCLK clocks exactly are and
> unfortunately I must agree with Krzysztof.  These clock gates are
> closely related to the IP blocks and to me proper approach is to
> have them listed in DT and controlled by the SPI bus driver.
> 
> I checked and there is similar pattern for other IPs like I2S and
> other SoCs, e.g. exynos7420.
> Additionally parents of those IOCLK_SPI?_CLK clocks are currently
> wrongly modelled as fixed rate clocks.  These clocks really don't
> have a parent until some clock is fed externally to the SoC's I/O
> pin.  But this issue could be addressed later.

yes, it's a weird design :/

> I think it is not a big deal to add "samsung-exynos5433-spi"
> compatible to the SPI driver along with a new variant data and
> a flag like "has_cmu_ioclk" to indicate whether a third clock
> should be handled or not. Presumably for now the ioclk clock can
> just simply be enabled in probe(), this way it will be enabled
> only for SPI controllers actually in use.

OK, I will work on s3c64xx driver side, then.

Thanks,
Andi

[PATCH v4 2/2] clk: exynos5433: enable sclk_ioclk for SPI3

[Andi Shyti]

enable SPI3 critical clocks by using the CLK_IS_CRITICAL flag.
There is no device which is supposed to enable this clock when
needed, therefore, the only way to use the SPI bus is to enable
it in boot time.

Suggested-by: Tomasz Figa <tomasz.figa@gmail.com>
Signed-off-by: Andi Shyti <andi.shyti@samsung.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
---
 drivers/clk/samsung/clk-exynos5433.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/samsung/clk-exynos5433.c b/drivers/clk/samsung/clk-exynos5433.c
index 337387b..fb8d330 100644
--- a/drivers/clk/samsung/clk-exynos5433.c
+++ b/drivers/clk/samsung/clk-exynos5433.c
@@ -1648,7 +1648,8 @@ static struct samsung_gate_clock peric_gate_clks[] __initdata = {
 	GATE(CLK_SCLK_IOCLK_SPI4, "sclk_ioclk_spi4", "ioclk_spi4_clk_in",
 			ENABLE_SCLK_PERIC, 21, CLK_SET_RATE_PARENT, 0),
 	GATE(CLK_SCLK_IOCLK_SPI3, "sclk_ioclk_spi3", "ioclk_spi3_clk_in",
-			ENABLE_SCLK_PERIC, 20, CLK_SET_RATE_PARENT, 0),
+			ENABLE_SCLK_PERIC, 20,
+			CLK_IS_CRITICAL | CLK_SET_RATE_PARENT, 0),
 	GATE(CLK_SCLK_SPI4, "sclk_spi4", "sclk_spi4_peric", ENABLE_SCLK_PERIC,
 			19, CLK_SET_RATE_PARENT, 0),
 	GATE(CLK_SCLK_SPI3, "sclk_spi3", "sclk_spi3_peric", ENABLE_SCLK_PERIC,
-- 
2.8.1

Re: [PATCH v4 0/2] mark spi clocks as critical and enable spi3 clocks

[Sylwester Nawrocki]

On 07/07/2016 02:13 PM, Andi Shyti wrote:
> Andi Shyti (2):
>   clk: exynos5433: do not use CLK_IGNORE_UNUSED for SPI clocks
>   clk: exynos5433: enable sclk_ioclk for SPI3

Applied both patches, thanks.

Re: [PATCH v4 0/2] mark spi clocks as critical and enable spi3 clocks

[Sylwester Nawrocki]

On 07/07/2016 03:18 PM, Sylwester Nawrocki wrote:
> On 07/07/2016 02:13 PM, Andi Shyti wrote:
>> > Andi Shyti (2):
>> >   clk: exynos5433: do not use CLK_IGNORE_UNUSED for SPI clocks
>> >   clk: exynos5433: enable sclk_ioclk for SPI3
>
> Applied both patches, thanks.

Apologies for the confusion, I had to drop these patches for reasons
explained in the other thread. We just need to simply drop
CLK_IGNORE_UNUSED flags and get the driver controlling clocks which
belong to the peripheral IP block.