linux-kernel - Re: [PATCH v6 2/5] dt-bindings: clock: Add AST2500/AST2600 HACE reset definition

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Date:   Wed, 29 Jun 2022 20:32:48 -0700
From:   Dhananjay Phadke <dphadke@...ux.microsoft.com>
To:     Neal Liu <neal_liu@...eedtech.com>,
        Corentin Labbe <clabbe.montjoie@...il.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Randy Dunlap <rdunlap@...radead.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>,
        Dhananjay Phadke <dhphadke@...rosoft.com>,
        Johnny Huang <johnny_huang@...eedtech.com>
Cc:     "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        BMC-SW <BMC-SW@...eedtech.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v6 2/5] dt-bindings: clock: Add AST2500/AST2600 HACE reset
 definition

On 6/29/2022 8:17 PM, Neal Liu wrote:
[...]
>> On 6/29/2022 2:44 AM, Neal Liu wrote:
>>> Add HACE reset bit definition for AST2500/AST2600.
>>>
>>> Signed-off-by: Neal Liu <neal_liu@...eedtech.com>
>>> Signed-off-by: Johnny Huang <johnny_huang@...eedtech.com>
>>> ---
>>>    include/dt-bindings/clock/aspeed-clock.h  | 1 +
>>>    include/dt-bindings/clock/ast2600-clock.h | 1 +
>>>    2 files changed, 2 insertions(+)
>>>
>>> diff --git a/include/dt-bindings/clock/aspeed-clock.h
>>> b/include/dt-bindings/clock/aspeed-clock.h
>>> index 9ff4f6e4558c..06d568382c77 100644
>>> --- a/include/dt-bindings/clock/aspeed-clock.h
>>> +++ b/include/dt-bindings/clock/aspeed-clock.h
>>> @@ -52,5 +52,6 @@
>>>    #define ASPEED_RESET_I2C		7
>>>    #define ASPEED_RESET_AHB		8
>>>    #define ASPEED_RESET_CRT1		9
>>> +#define ASPEED_RESET_HACE		10
>>
>> NAK.
>>
>> I replied to older v5 of this patch, but this v6 also looks incorrect as per HW
>> manual.
>>
>> https://lore.kernel.org/linux-arm-kernel/20220629032008.1579899-1-neal_liu
>> @aspeedtech.com/T/#m000bd3388b3e41117aa0eef10bf6f8a6a3a85cce
>>
>> For both AST2400 and AST2500:
>> SCU04[10] = PECI.
>>
>> It will be best to refactor/split aspeed-clock.h into separate files.
> 
> Hi, based on @Krzysztof mentioned, change these define is not allowed due to breaking ABI.
> So another way is to define a new value(interface), and we can change driver's implementation.
> I know this is not intuitive to hardware register's value, it also confused me at the first time.
> 
> 

This is not SW ABI issue. Each controller in the device-tree needs
correct clock and reset paths. aspeed-clock.h is shared between g4 and 
g5 dtsi. Not sure how you picked bit 10 for HACE, it's for resetting
PECI controller.

See drivers/clk/clk-aspeed.c, which BTW is duplicating same stuff.
         [ASPEED_RESET_MIC]      = 18,
         [ASPEED_RESET_PWM]      =  9,
         [ASPEED_RESET_PECI]     = 10,

FWIW, the reset bit for HACE and MIC are interchanged for AST2400 and 
AST2500 (at least as per HW datasheet).

So this is really fixing what's apparently already broken.

Regards,
Dhananjay