[PATCH v3 0/2] mark spi clocks as critical and enable spi3 clocks

[PATCH v3 0/2] mark spi clocks as critical and enable spi3 clocks

[Andi Shyti]

Hi,

This patchset enables spi3 clocks by marking critical clocks as
CLK_IS_CRITICAL and in the meantime replaces the use of
CLK_IGNORE_UNUSED for spi1 clocks.

The sclk needs to be considered critical as well.

The SPI3 in the tm2/tm2e boards will control an irled for remote
controlling.

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.

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 | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

-- 
2.8.1

[PATCH v3 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..1f7c4951 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_IS_CRITICAL | 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

[PATCH v3 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 | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/samsung/clk-exynos5433.c b/drivers/clk/samsung/clk-exynos5433.c
index 1f7c4951..e769c80 100644
--- a/drivers/clk/samsung/clk-exynos5433.c
+++ b/drivers/clk/samsung/clk-exynos5433.c
@@ -1648,11 +1648,12 @@ 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,
-			18, CLK_SET_RATE_PARENT, 0),
+			18, CLK_IS_CRITICAL | CLK_SET_RATE_PARENT, 0),
 	GATE(CLK_SCLK_SCI, "sclk_sci", "div_sclk_sci", ENABLE_SCLK_PERIC,
 			17, 0, 0),
 	GATE(CLK_SCLK_SC_IN, "sclk_sc_in", "div_sclk_sc_in", ENABLE_SCLK_PERIC,
-- 
2.8.1

Re: [PATCH v3 0/2] mark spi clocks as critical and enable spi3 clocks

[Tomasz Figa]

Hi Andi,

2016-06-30 16:15 GMT+09:00 Andi Shyti <andi.shyti@samsung.com>:
> Hi,
>
> This patchset enables spi3 clocks by marking critical clocks as
> CLK_IS_CRITICAL and in the meantime replaces the use of
> CLK_IGNORE_UNUSED for spi1 clocks.
>
> The sclk needs to be considered critical as well.
>
> The SPI3 in the tm2/tm2e boards will control an irled for remote
> controlling.
>
> 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!

This sounds like a DTS and/or SPI and/or clock driver bug then. I'm
pretty much convinced that it might also cause other problems and this
workaround will only mask them making things even more difficult to
debug in the future. Let's not introduce more technical debt.

Best regards,
Tomasz

Re: [PATCH v3 0/2] mark spi clocks as critical and enable spi3 clocks

[Andi Shyti]

Hi Tomasz,

> > This patchset enables spi3 clocks by marking critical clocks as
> > CLK_IS_CRITICAL and in the meantime replaces the use of
> > CLK_IGNORE_UNUSED for spi1 clocks.
> >
> > The sclk needs to be considered critical as well.
> >
> > The SPI3 in the tm2/tm2e boards will control an irled for remote
> > controlling.
> >
> > 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!
> 
> This sounds like a DTS and/or SPI and/or clock driver bug then. I'm
> pretty much convinced that it might also cause other problems and this
> workaround will only mask them making things even more difficult to
> debug in the future. Let's not introduce more technical debt.

In principle I agree, but, the upcoming TM2/TM2e boards will have
the audio codec connected on SPI1 and the ir remote controller on
the SPI3 (others SPI slots are used as well, but we don't have
the drivers ready for them).

I followed for SPI3 the same approach as it was done for SPI1, so
that I see two choices here:

 * reject this patches and cleanup the SPI1 from the "technical
   debt" and not have anything working on spi.

or

 * do for SPI3 the same as it has been done for SPI1 (and as it
   is now) with its "technical debt".

I did quite an extensive testing on these lines and I don't see
any other alternative.

Thanks,
Andi

Re: [PATCH v3 0/2] mark spi clocks as critical and enable spi3 clocks

[Tomasz Figa]

2016-07-04 13:20 GMT+09:00 Andi Shyti <andi.shyti@samsung.com>:
> Hi Tomasz,
>
>> > This patchset enables spi3 clocks by marking critical clocks as
>> > CLK_IS_CRITICAL and in the meantime replaces the use of
>> > CLK_IGNORE_UNUSED for spi1 clocks.
>> >
>> > The sclk needs to be considered critical as well.
>> >
>> > The SPI3 in the tm2/tm2e boards will control an irled for remote
>> > controlling.
>> >
>> > 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!
>>
>> This sounds like a DTS and/or SPI and/or clock driver bug then. I'm
>> pretty much convinced that it might also cause other problems and this
>> workaround will only mask them making things even more difficult to
>> debug in the future. Let's not introduce more technical debt.
>
> In principle I agree, but, the upcoming TM2/TM2e boards will have
> the audio codec connected on SPI1 and the ir remote controller on
> the SPI3 (others SPI slots are used as well, but we don't have
> the drivers ready for them).
>
> I followed for SPI3 the same approach as it was done for SPI1, so
> that I see two choices here:
>
>  * reject this patches and cleanup the SPI1 from the "technical
>    debt" and not have anything working on spi.

>
> or
>
>  * do for SPI3 the same as it has been done for SPI1 (and as it
>    is now) with its "technical debt".
>
> I did quite an extensive testing on these lines and I don't see
> any other alternative.

The SPI driver is supposed to enable the SPI bus clock whenever
necessary, if it's given the clock correctly and the clock driver has
the clock hierarchy correctly defined. So I see third choice here:

 * Debug why the SPI driver doesn't properly enable the clock, fix the
cause (fixing both SPI1 and SPI3 sclk at the same time) and then
remove the CLK_IGNORE_UNUSED flag from sclk_spi1.

Of course the above doesn't apply to sclk_ioclk clocks, as we already
agreed that they need CLK_IS_CRITICAL due to their nature.

Best regards,
Tomasz

Re: [PATCH v3 1/2] clk: exynos5433: do not use CLK_IGNORE_UNUSED for SPI clocks

[Sylwester Nawrocki]

On 06/30/2016 09:15 AM, Andi Shyti wrote:
> The CLK_IGNORE_UNUSED flag has to be avoided whenever possible.

In general I would rather disagree.

> 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..1f7c4951 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 = {

> @@ -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_IS_CRITICAL | CLK_SET_RATE_PARENT, 0),

As Tomasz pointed out, this should be addressed in the driver/dts,
we shouldn't be patching board configurations into a per-SoC driver.
Other boards may want to keep this clock disabled.

What is an exact problem here, are you perhaps testing suspend to RAM?
I tested my sound support patches on top of v4.7-rc1 and everything
seemed to work well, I didn't notice any issues with the audio codec
which was the only slave on the SPI 1 bus.

Doesn't it help when you specify CLK_SCLK_SPI1 as the second clock
("spi_busclk0") of the spi_1 bus controller instead of
CLK_SCLK_SPI0_PERIC? CLK_SCLK_SPI0_PERIC seem to be parent of
CLK_SCLK_SPI1 so the enable state would be propagated.

Re: [PATCH v3 1/2] clk: exynos5433: do not use CLK_IGNORE_UNUSED for SPI clocks

[Andi Shyti]

Hi Sylwester,

> >  	GATE(CLK_SCLK_SPI1, "sclk_spi1", "sclk_spi1_peric", ENABLE_SCLK_PERIC,
> > -			4, CLK_IGNORE_UNUSED | CLK_SET_RATE_PARENT, 0),
> > +			4, CLK_IS_CRITICAL | CLK_SET_RATE_PARENT, 0),
> 
> As Tomasz pointed out, this should be addressed in the driver/dts,
> we shouldn't be patching board configurations into a per-SoC driver.
> Other boards may want to keep this clock disabled.

The single clock lines are not configured in the exynos5433 dts,
but in the drivers/clk/samsung/clk-exynos5433.c file and it's the
only place where we can set the flags.

> What is an exact problem here, are you perhaps testing suspend to RAM?
> I tested my sound support patches on top of v4.7-rc1 and everything
> seemed to work well, I didn't notice any issues with the audio codec
> which was the only slave on the SPI 1 bus.

Yes, because the audio codec is on SPI1 and its bus line
(spi_busclk0) is CLK_SCLK_SPI1_PERIC while the CLK_SCLK_SPI1 is
set as CLK_IGNORE_UNUSED.

> Doesn't it help when you specify CLK_SCLK_SPI1 as the second clock
> ("spi_busclk0") of the spi_1 bus controller instead of
> CLK_SCLK_SPI0_PERIC? CLK_SCLK_SPI0_PERIC seem to be parent of
> CLK_SCLK_SPI1 so the enable state would be propagated.

nope! :(

For some reasons, if you set in the DTS as spi_busclk0 the
CLK_SCLK_SPI1 from cmu_peric you get a synchronus abort in the
s3c64xx_spi_config (the first read performed on the device).

Andi

Re: [PATCH v3 1/2] clk: exynos5433: do not use CLK_IGNORE_UNUSED for SPI clocks

[Sylwester Nawrocki]

On 07/04/2016 12:26 PM, Andi Shyti wrote:
 
> The single clock lines are not configured in the exynos5433 dts,
> but in the drivers/clk/samsung/clk-exynos5433.c file and it's the
> only place where we can set the flags.

I meant we could amend which clocks are specified at the SPI bus device
DT nodes and change handling of clocks in the spi-s3c64xx driver to model
everything properly and get it all working.
 
>> What is an exact problem here, are you perhaps testing suspend to RAM?
>> I tested my sound support patches on top of v4.7-rc1 and everything
>> seemed to work well, I didn't notice any issues with the audio codec
>> which was the only slave on the SPI 1 bus.
> 
> Yes, because the audio codec is on SPI1 and its bus line
> (spi_busclk0) is CLK_SCLK_SPI1_PERIC while the CLK_SCLK_SPI1 is
> set as CLK_IGNORE_UNUSED.

That's true, looking at a downstream kernel I see that there is just plain 
div clock specified for spi_busclk0 (DIVsclk_spi1_b), i.e. SCLK_SPI1_PERIC 
and SCLK_SPI1 don't get disabled in s3c64xx_spi_config().
It seems SCLK_SPI1 in CMU_PERIC need to be kept enabled while accessing 
the SPI controller's registers.

>> Doesn't it help when you specify CLK_SCLK_SPI1 as the second clock
>> ("spi_busclk0") of the spi_1 bus controller instead of
>> CLK_SCLK_SPI0_PERIC? CLK_SCLK_SPI0_PERIC seem to be parent of
>> CLK_SCLK_SPI1 so the enable state would be propagated.
> 
> nope! :(
> 
> For some reasons, if you set in the DTS as spi_busclk0 the
> CLK_SCLK_SPI1 from cmu_peric you get a synchronus abort in the
> s3c64xx_spi_config (the first read performed on the device).

Indeed, I also observed that, after removing CLK_IGNORE_UNUSED from 
the CLK_SCLK_SPI1 clock. 

After discussion with Krzysztof and Andrzej I came up with a patch as below 
where there is no aborts, the sound works and clocks are not kept always 
enabled:

root@localhost:~# cat /sys/kernel/debug/clk/clk_summary | grep spi1
 ioclk_spi1_clk_in                        0            0    50000000          0 0  
    sclk_ioclk_spi1                       0            0    50000000          0 0  
          pclk_isp_spi1                   0            0     6000000          0 0  
    mout_sclk_isp_spi1_user               0            0    24000000          0 0  
       sclk_isp_spi1                      0            0    24000000          0 0  
    mout_sclk_spi1                        0            0    24000000          0 0  
       div_sclk_spi1_a                    0            0     3000000          0 0  
          div_sclk_spi1_b                 0            0     3000000          0 0  
             sclk_spi1_peric              0            0     3000000          0 0  
                sclk_spi1                 0            0     3000000          0 0  
    mout_sclk_isp_spi1                    0            0    24000000          0 0  
       div_sclk_isp_spi1_a                0            0     3000000          0 0  
          div_sclk_isp_spi1_b             0            0       25000          0 0  
             sclk_isp_spi1_cam1           0            0       25000          0 0  
                      pclk_spi1           0            0    66666667          0 0  

I'm not yet 100% sure if it is a correct approach, the downstream kernel uses
"global-per-IP" gate clocks (ENABLE_IP_PERIC? registers), that gate all clocks 
to a given IP block and those clocks are not defined in mainline at all, but 
it seems we just need to amend the SPI controller driver to not be disabling
sdd->src_clk clock before accessing registers. 
Or maybe to pass only DIVsclk_spi?_b as spi_busclk0 in DT nodes and add 
SCLK_SPI0 from CMU_PERIC as a third SPI device clock for exynos5433.

-----------8<------------
diff --git a/arch/arm64/boot/dts/exynos/exynos5433.dtsi b/arch/arm64/boot/dts/exynos/exynos5433.dtsi
index 8e124fc..f444c66 100644
--- a/arch/arm64/boot/dts/exynos/exynos5433.dtsi
+++ b/arch/arm64/boot/dts/exynos/exynos5433.dtsi
@@ -617,8 +617,13 @@
                        dma-names = "tx", "rx";
                        #address-cells = <1>;
                        #size-cells = <0>;
+#if 0
                        clocks = <&cmu_peric CLK_PCLK_SPI1>,
                                 <&cmu_top CLK_SCLK_SPI1_PERIC>;
+#else
+                       clocks = <&cmu_peric CLK_PCLK_SPI1>,
+                                <&cmu_peric CLK_SCLK_SPI1>;
+#endif
                        clock-names = "spi", "spi_busclk0";
                        samsung,spi-src-clk = <0>;
                        pinctrl-names = "default";
diff --git a/drivers/clk/samsung/clk-exynos5433.c b/drivers/clk/samsung/clk-exynos5433.c
index e3cc935..61d5643 100644
--- a/drivers/clk/samsung/clk-exynos5433.c
+++ b/drivers/clk/samsung/clk-exynos5433.c
@@ -1675,7 +1675,7 @@ 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",
diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c
index 5a76a50..2cb965c 100644
--- a/drivers/spi/spi-s3c64xx.c
+++ b/drivers/spi/spi-s3c64xx.c
@@ -578,7 +578,7 @@ static void s3c64xx_spi_config(struct s3c64xx_spi_driver_data *sdd)
 
        /* Disable Clock */
        if (sdd->port_conf->clk_from_cmu) {
-               clk_disable_unprepare(sdd->src_clk);
+               /* clk_disable_unprepare(sdd->src_clk); */
        } else {
                val = readl(regs + S3C64XX_SPI_CLK_CFG);
                val &= ~S3C64XX_SPI_ENCLK_ENABLE;
@@ -626,7 +626,7 @@ static void s3c64xx_spi_config(struct s3c64xx_spi_driver_data *sdd)
                /* There is half-multiplier before the SPI */
                clk_set_rate(sdd->src_clk, sdd->cur_speed * 2);
                /* Enable Clock */
-               clk_prepare_enable(sdd->src_clk);
+               /* clk_prepare_enable(sdd->src_clk); */
        } else {
                /* Configure Clock */
                val = readl(regs + S3C64XX_SPI_CLK_CFG);
-----------8<------------

Re: [PATCH v3 1/2] clk: exynos5433: do not use CLK_IGNORE_UNUSED for SPI clocks

[Andi Shyti]

Hi Sylwester,

> +#if 0
>                         clocks = <&cmu_peric CLK_PCLK_SPI1>,
>                                  <&cmu_top CLK_SCLK_SPI1_PERIC>;
> +#else
> +                       clocks = <&cmu_peric CLK_PCLK_SPI1>,
> +                                <&cmu_peric CLK_SCLK_SPI1>;
> +#endif

Yes, that's how it should be, indeed.

>         /* Disable Clock */
>         if (sdd->port_conf->clk_from_cmu) {
> -               clk_disable_unprepare(sdd->src_clk);
> +               /* clk_disable_unprepare(sdd->src_clk); */
>         } else {
>                 val = readl(regs + S3C64XX_SPI_CLK_CFG);
>                 val &= ~S3C64XX_SPI_ENCLK_ENABLE;
> @@ -626,7 +626,7 @@ static void s3c64xx_spi_config(struct s3c64xx_spi_driver_data *sdd)
>                 /* There is half-multiplier before the SPI */
>                 clk_set_rate(sdd->src_clk, sdd->cur_speed * 2);
>                 /* Enable Clock */
> -               clk_prepare_enable(sdd->src_clk);
> +               /* clk_prepare_enable(sdd->src_clk); */
>         } else {
>                 /* Configure Clock */
>                 val = readl(regs + S3C64XX_SPI_CLK_CFG);

I don't see anything wrong on the above. We could make it as:

@@ -596,9 +597,7 @@ static void s3c64xx_spi_config(struct s3c64xx_spi_driver_data *sdd)
        u32 val;
 
        /* Disable Clock */
-       if (sdd->port_conf->clk_from_cmu) {
-               clk_disable_unprepare(sdd->src_clk);
-       } else {
+       if (!sdd->port_conf->clk_from_cmu) {
                val = readl(regs + S3C64XX_SPI_CLK_CFG);
                val &= ~S3C64XX_SPI_ENCLK_ENABLE;
                writel(val, regs + S3C64XX_SPI_CLK_CFG);
@@ -640,13 +639,7 @@ static void s3c64xx_spi_config(struct s3c64xx_spi_driver_data *sdd)
 
        writel(val, regs + S3C64XX_SPI_MODE_CFG);
 
-       if (sdd->port_conf->clk_from_cmu) {
-               /* Configure Clock */
-               /* There is half-multiplier before the SPI */
-               clk_set_rate(sdd->src_clk, sdd->cur_speed * 2);
-               /* Enable Clock */
-               clk_prepare_enable(sdd->src_clk);
-       } else {
+       if (!sdd->port_conf->clk_from_cmu) {
                /* Configure Clock */
                val = readl(regs + S3C64XX_SPI_CLK_CFG);
                val &= ~S3C64XX_SPI_PSR_MASK;

> I meant we could amend which clocks are specified at the SPI bus device
> DT nodes and change handling of clocks in the spi-s3c64xx driver to model
> everything properly and get it all working.

I think that if the clock comes from the cmu it's not necessary
to disable it. I would like to avoid adding DTS properties
because we have the clock disabling inherited from old code which
it might not be required at all (in our tests, indeed it works).

Thanks,
Andi

Re: [PATCH v3 1/2] clk: exynos5433: do not use CLK_IGNORE_UNUSED for SPI clocks

[Sylwester Nawrocki]

On 07/06/2016 06:51 AM, Andi Shyti wrote:
> 
> I don't see anything wrong on the above. We could make it as:

> @@ -640,13 +639,7 @@ static void s3c64xx_spi_config(struct s3c64xx_spi_driver_data *sdd)
>  
>         writel(val, regs + S3C64XX_SPI_MODE_CFG);
>  
> -       if (sdd->port_conf->clk_from_cmu) {
> -               /* Configure Clock */
> -               /* There is half-multiplier before the SPI */
> -               clk_set_rate(sdd->src_clk, sdd->cur_speed * 2);
> -               /* Enable Clock */
> -               clk_prepare_enable(sdd->src_clk);

clk_set_rate() call needs to stay, we can only remove clk_prepare_enable().

> -       } else {
> +       if (!sdd->port_conf->clk_from_cmu) {
>                 /* Configure Clock */
>                 val = readl(regs + S3C64XX_SPI_CLK_CFG);
>                 val &= ~S3C64XX_SPI_PSR_MASK;
> 
>> I meant we could amend which clocks are specified at the SPI bus device
>> DT nodes and change handling of clocks in the spi-s3c64xx driver to model
>> everything properly and get it all working.
> 
> I think that if the clock comes from the cmu it's not necessary
> to disable it. I would like to avoid adding DTS properties
> because we have the clock disabling inherited from old code which
> it might not be required at all (in our tests, indeed it works).

OK, anyway we already need to amend exynos5433.dtsi file to change
the "spi_busclk0" clock specifier.

I agree we can get rid of the clock gating in s3c64xx_spi_config() 
function, it should not do any harm and will help in getting rid 
of the bus access exceptions.

In general PCLK should be enough for accessing register of the controller,
one hypothesis is that automatic clock gating may be disabling PCLK
when it sees SCLK inactive.

I tested on exynos4412 trats2 board a large firmware file upload over 
SPI and didn't notice any bad side effects with above 
clk_disable_unprepare()/clk_prepare_enable() calls commented out.