netdev - Re: stmmac DT property snps,axi

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Date:   Mon, 12 Dec 2016 14:16:52 +0100
From:   Giuseppe CAVALLARO <peppe.cavallaro@...com>
To:     Alexandre Torgue <alexandre.torgue@...com>,
        Niklas Cassel <niklas.cassel@...s.com>
CC:     <netdev@...r.kernel.org>
Subject: Re: stmmac DT property snps,axi_all

Hello

On 12/9/2016 5:06 PM, Alexandre Torgue wrote:
> Hi Niklas
>
> On 12/09/2016 10:53 AM, Niklas Cassel wrote:
>> On 12/09/2016 10:20 AM, Niklas Cassel wrote:
>>> On 12/08/2016 02:36 PM, Alexandre Torgue wrote:
>>>> Hi Niklas,
>>>>
>>>> On 12/05/2016 05:18 PM, Niklas Cassel wrote:
>>>>> Hello Giuseppe
>>>>>
>>>>>
>>>>> I'm trying to figure out what snps,axi_all is supposed to represent.
>>>>>
>>>>> It appears that the value is saved, but never used in the code.
>>>>>
>>>>> Looking at the register specification, I'm guessing that it represents
>>>>> Address-Aligned Beats, but there is already the property snps,aal
>>>>> for that.
>>>> IMO, it is not useful. Indeed AXI_AAL is a read only bit (in AXI bus
>>>> mode register) and reflects the aal bit in DMA bus register.
>>>> As you know we use "snps,aal" to set aal bit in DMA bus register.
>>>> So "snps,axi_all" entry seems useless. Let's see with Peppe.
>>> Ok, I see. GMAC and GMAC4 is different here.
>>>
>>> For GMAC4 AAL only exists in DMA_SYS_BUS_MODE.
>>> It's not reflected anywhere else.
>>>
>>> The code is correct in the driver.
>>>
>>> If snps,axi_all is just created for a read-only register,
>>> and it is currently never used in the code,
>>> while we have snps,aal, which is correct and works,
>>> I guess it should be ok to remove snps,axi_all.
>>>
>>> I can cook up a patch.
>>>
>>
>> Here we go :)
>>
>> I will send it as a real patch once net-next reopens.
>
> Thanks ;). Just check with Peppe next week (as he added in the past this
> property).

Yes, we can conclude that the axi_all can be safely removed from DT, in
fact on all GMACs the AaL will be set via DMA_BUS_MODE register.

peppe