linux-kernel - Re: [PATCH 02/13] dt-bindings: clock: google,gs101-clock: add PERIC0 clock management unit

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Date: Wed, 27 Dec 2023 12:38:21 +0000
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Peter Griffin <peter.griffin@...aro.org>
Cc: sboyd@...nel.org, conor+dt@...nel.org, andi.shyti@...nel.org,
 alim.akhtar@...sung.com, gregkh@...uxfoundation.org, jirislaby@...nel.org,
 catalin.marinas@....com, will@...nel.org, s.nawrocki@...sung.com,
 tomasz.figa@...il.com, cw00.choi@...sung.com, arnd@...db.de,
 semen.protsenko@...aro.org, andre.draszik@...aro.org, saravanak@...gle.com,
 willmcvicker@...gle.com, linux-arm-kernel@...ts.infradead.org,
 linux-samsung-soc@...r.kernel.org, linux-clk@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-i2c@...r.kernel.org, linux-serial@...r.kernel.org,
 André Draszik <andre.draszik@...aro.org>
Subject: Re: [PATCH 02/13] dt-bindings: clock: google,gs101-clock: add PERIC0
 clock management unit

Hi, Rob,

On 12/21/23 07:20, Tudor Ambarus wrote:
> 
> 
> On 12/20/23 15:07, Rob Herring wrote:
>> On Thu, Dec 14, 2023 at 10:52:32AM +0000, Tudor Ambarus wrote:
>>> Add dt-schema documentation for the Connectivity Peripheral 0 (PERIC0)
>>> clock management unit.
>>>
>>> Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
>>> ---
>>>  .../bindings/clock/google,gs101-clock.yaml    | 25 +++++-
>>>  include/dt-bindings/clock/google,gs101.h      | 86 +++++++++++++++++++
>>>  2 files changed, 109 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/clock/google,gs101-clock.yaml b/Documentation/devicetree/bindings/clock/google,gs101-clock.yaml
>>> index 3eebc03a309b..ba54c13c55bc 100644
>>> --- a/Documentation/devicetree/bindings/clock/google,gs101-clock.yaml
>>> +++ b/Documentation/devicetree/bindings/clock/google,gs101-clock.yaml
>>> @@ -30,14 +30,15 @@ properties:
>>>        - google,gs101-cmu-top
>>>        - google,gs101-cmu-apm
>>>        - google,gs101-cmu-misc
>>> +      - google,gs101-cmu-peric0
>>>  
>>>    clocks:
>>>      minItems: 1
>>> -    maxItems: 2
>>> +    maxItems: 3
>>>  
>>>    clock-names:
>>>      minItems: 1
>>> -    maxItems: 2
>>> +    maxItems: 3
>>>  
>>>    "#clock-cells":
>>>      const: 1
>>> @@ -88,6 +89,26 @@ allOf:
>>>              - const: dout_cmu_misc_bus
>>>              - const: dout_cmu_misc_sss
>>>  
>>> +  - if:
>>> +      properties:
>>> +        compatible:
>>> +          contains:
>>> +            const: google,gs101-cmu-peric0
>>> +
>>> +    then:
>>> +      properties:
>>> +        clocks:
>>> +          items:
>>> +            - description: External reference clock (24.576 MHz)
>>> +            - description: Connectivity Peripheral 0 bus clock (from CMU_TOP)
>>> +            - description: Connectivity Peripheral 0 IP clock (from CMU_TOP)
>>> +
>>> +        clock-names:
>>> +          items:
>>> +            - const: oscclk
>>> +            - const: dout_cmu_peric0_bus
>>> +            - const: dout_cmu_peric0_ip
>>
>> 'bus' and 'ip' are sufficient because naming is local to the module. The 
>> same is true on 'dout_cmu_misc_bus'. As that has not made a release, 
>> please fix all of them.
>>
> 
> Ok, will fix them shortly. Thanks, Rob!

I tried your suggestion at
https://lore.kernel.org/linux-arm-kernel/c6cc6e74-6c3d-439b-8dc1-bc50a88a3d8f@linaro.org/

and we noticed that we'd have to update the clock driver as well.
These CMUs set the DT clock-name of the parent clock in the driver in
struct samsung_cmu_info::clk_name[]. The driver then tries to enable the
parent clock based on the clock-name in exynos_arm64_register_cmu().

In order to enable the parent clock of the CMU the following would be
needed in the driver:

diff --git a/drivers/clk/samsung/clk-gs101.c
b/drivers/clk/samsung/clk-gs101.c
index 68a27b78b00b..e91836ea3a98 100644
--- a/drivers/clk/samsung/clk-gs101.c
+++ b/drivers/clk/samsung/clk-gs101.c
@@ -2476,7 +2476,7 @@ static const struct samsung_cmu_info misc_cmu_info
__initconst = {
        .nr_clk_ids             = CLKS_NR_MISC,
        .clk_regs               = misc_clk_regs,
        .nr_clk_regs            = ARRAY_SIZE(misc_clk_regs),
-       .clk_name               = "dout_cmu_misc_bus",
+       .clk_name               = "bus",
 };

I think I lean towards keeping the name as it was because it's clearer
what are the clock dependencies in the driver. "dout_cmu_misc_bus" is
the clock name used when defining the clock:
DIV(CLK_DOUT_CMU_MISC_BUS, "dout_cmu_misc_bus", "gout_cmu_misc_bus",
    CLK_CON_DIV_CLKCMU_MISC_BUS, 0, 4),
The other exynos clock drivers are using too the driver's clock names
for the clock-names device tree property. For consistency I'd keep it
the same.

If you have a stronger opinion than mine, please tell and I'll happily
update the driver.

Thanks,
ta