linux-kernel - Re: [PATCH v2] stmmac: CSR clock configuration fix

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Message-ID: <2dad580c-7c59-f680-0e99-c4af54fb794b@synopsys.com>
Date:   Fri, 23 Dec 2016 10:09:02 +0000
From:   Joao Pinto <Joao.Pinto@...opsys.com>
To:     Phil Reid <preid@...ctromag.com.au>,
        Joao Pinto <Joao.Pinto@...opsys.com>, <peppe.cavallaro@...com>,
        <davem@...emloft.net>, <seraphin.bonnaffe@...com>
CC:     <hock.leong.kweh@...el.com>, <niklas.cassel@...s.com>,
        <pavel@....cz>, <linux-kernel@...r.kernel.org>,
        <netdev@...r.kernel.org>
Subject: Re: [PATCH v2] stmmac: CSR clock configuration fix


Hello Phil,

Às 1:09 AM de 12/23/2016, Phil Reid escreveu:
> G'day Joao,
> On 23/12/2016 01:06, Joao Pinto wrote:
>> Às 4:57 PM de 12/22/2016, Phil Reid escreveu:
>>> On 22/12/2016 23:47, Joao Pinto wrote:
>>>>
>>>> Hello Phil,
>>>>
>>>> Às 3:42 PM de 12/22/2016, Phil Reid escreveu:
>>>>> G'day Joao,
>>>>>
>>>>> On 22/12/2016 20:38, Joao Pinto wrote:
>>>>>> When testing stmmac with my QoS reference design I checked a problem in the
>>>>>> CSR clock configuration that was impossibilitating the phy discovery, since
>>>>>> every read operation returned 0x0000ffff. This patch fixes the issue.
>>>>>>
>>>>>> Signed-off-by: Joao Pinto <jpinto@...opsys.com>
>>>>>> ---
>>>>>> changes v1->v2 (David Miller)
>>>>>> - DWMAC100 and DWMAC1000 csr clocks masks should also be fixed for the patch
>>>>>> to make sense
>>>>>>
>>>>>>  drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c | 2 +-
>>>>>>  drivers/net/ethernet/stmicro/stmmac/dwmac100_core.c  | 2 +-
>>>>>>  drivers/net/ethernet/stmicro/stmmac/stmmac_mdio.c    | 8 ++++----
>>>>>>  3 files changed, 6 insertions(+), 6 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c
>>>>>> b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c
>>>>>> index b21d03f..94223c8 100644
>>>>>> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c
>>>>>> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac1000_core.c
>>>>>> @@ -539,7 +539,7 @@ struct mac_device_info *dwmac1000_setup(void __iomem
>>>>>> *ioaddr, int mcbins,
>>>>>>      mac->mii.reg_shift = 6;
>>>>>>      mac->mii.reg_mask = 0x000007C0;
>>>>>>      mac->mii.clk_csr_shift = 2;
>>>>>> -    mac->mii.clk_csr_mask = 0xF;
>>>>>> +    mac->mii.clk_csr_mask = GENMASK(4, 2);
>>>>>
>>>>> Should this not be GENMASK(5,2)
>>>>
>>>> According to Universal MAC databook (valid for MAC100 and MAC1000), we have:
>>>>
>>>> Bits: 4:2
>>>> 000 60-100 MHz clk_csr_i/42
>>>> 001 100-150 MHz clk_csr_i/62
>>>> 010 20-35 MHz clk_csr_i/16
>>>> 011 35-60 MHz clk_csr_i/26
>>>> 100 150-250 MHz clk_csr_i/102
>>>> 101 250-300 MHz clk_csr_i/124
>>>> 110, 111 Reserved
>>>>
>>>> So only bits 2, 3 and 4 should be masked.
>>>>
>>>> Thanks.
>>>>
>>> But this is a change in behaviour from what was there isn't.
>>> Previous mask was 4 bits. now it's 3.
>>>
>>> And for example the altera socfgpa implementation in the cyclone V has valid
>>> values
>>> for values 0x8-0xf, using bit 5:2.
>>
>> According to the databook, bit 5 is reserved and RO. When reserved, it is
>> possible to customize. Is that the case? If there is hardware using the 5th bit
>> we can put it GENMASK(5, 2) with no problem.
>>
> I've also checked the Aria 10 documentation and bit 5 is also RW.
> The following options are documented and supported
>     1000: CSR clock/4
>     1001: CSR clock/6
>     1010: CSR clock/8
>     1011: CSR clock/10
>     1100: CSR clock/12
>     1101: CSR clock/14
>     1110: CSR clock/16
>     1111: CSR clock/18
> They do mention that these values will probably be outside the IEEE 802.3
> specified range.
> 
> But there's at least a couple of cores out there where GENMASK(5,2) is valid.
> Can't say if anyone is using that setting thou.

Thanks for checking it! Ok, it seems like they are using the reserved bit 5. No
problem, I am going to change the patch and put the mask from 2 to 5. Thanks for
your help!

Joao

> 
>