linux-kernel - Re: [PATCH v2 1/5] phy: berlin-sata: Move PHY

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Message-ID: <544E8FDB.109@gmail.com>
Date:	Mon, 27 Oct 2014 19:32:59 +0100
From:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
To:	Kishon Vijay Abraham I <kishon@...com>, balbi@...com
CC:	Antoine Ténart 
	<antoine.tenart@...e-electrons.com>, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/5] phy: berlin-sata: Move PHY_BASE into private data
 struct

On 10/27/2014 01:27 PM, Kishon Vijay Abraham I wrote:
> On Saturday 25 October 2014 01:55 AM, Felipe Balbi wrote:
>> On Fri, Oct 24, 2014 at 10:14:55PM +0200, Sebastian Hesselbarth wrote:
>>> On 21.10.2014 11:40, Sebastian Hesselbarth wrote:
>>>> On 10/21/2014 11:33 AM, Kishon Vijay Abraham I wrote:
>>>>> On Tuesday 21 October 2014 02:37 PM, Sebastian Hesselbarth wrote:
>>>>>> Currently, Berlin SATA PHY driver assumes PHY_BASE address being
>>>>>> constant. While this PHY_BASE is correct for BG2Q, older BG2 PHY_BASE
>>>>>> is different. Prepare the driver for BG2 support by moving the phy_base
>>>>>> into private driver data.
>>>>>>
>>>>>> Acked-by: Antoine Ténart <antoine.tenart@...e-electrons.com>
>>>>>> Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
>>>> ...
>>>>>> ---
>>>>>>   drivers/phy/phy-berlin-sata.c | 42
>>>>>> ++++++++++++++++++++++++++++--------------
>>>>>>   1 file changed, 28 insertions(+), 14 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/phy/phy-berlin-sata.c
>>>>>> b/drivers/phy/phy-berlin-sata.c
>>>>>> index 69ced52d72aa..9682b0f66177 100644
>>>>>> --- a/drivers/phy/phy-berlin-sata.c
>>>>>> +++ b/drivers/phy/phy-berlin-sata.c
>>>>>> @@ -30,7 +30,7 @@
>>>>>>   #define MBUS_WRITE_REQUEST_SIZE_128    (BIT(2) << 16)
>>>>>>   #define MBUS_READ_REQUEST_SIZE_128    (BIT(2) << 19)
>>>>>>
>>>>>> -#define PHY_BASE        0x200
>>>>>> +#define BG2Q_PHY_BASE        0x200
>>>> [...]
>>>>>> +static u32 bg2q_sata_phy_base = BG2Q_PHY_BASE;
>>>>>> +
>>>>>> +static const struct of_device_id phy_berlin_sata_of_match[] = {
>>>>>> +    {
>>>>>> +        .compatible = "marvell,berlin2q-sata-phy",
>>>>>> +        .data = &bg2q_sata_phy_base,
>>>>>
>>>>> Can't the base directly come from dt?
>>>>
>>>> You are suggesting a "marvell,phy-base-address" property, right?
>>>> I have no strong opinion about it, I accept your call (or DT maintainer
>>>> ones).
>>>
>>> I still have the DT patches for BG2Q queued up for v3.19 (I missed the
>>> arm-soc merge window for v3.18). That means, there has been no release
>>> with the phy binding used and I can rework a little more.
>>>
>>> Can you please confirm that you want a DT property for the phy base address,
>>> e.g. marvell,phy-base-address = <{0x200,0x80}> ?
>>>
>>> If so, I'd also rename the compatible from berlin2q-sata-phy to more
>>> generic berlin-sata-phy.
>>
>> I think what Kishon is asking, is why this 0x200 offset isn't already on
>> reg. so that instead of, e.g.:
>>
>> 	reg = <0x40000000 0x1000>;
>>
>> you would have:
>>
>> 	reg = <0x40000200 0x1000>;
>
> I had something similar to what Sebastian suggested in mind. I think phy_base
> is used for a different reason and can't be directly used in 'reg'.

Kishon,

thanks for the clarification. While the extra marvell,phy-base-address
property basically works and I agree with it, I may have some
_potential_ draw-backs:

The Marvell BSP code (which I have no clue _why_ it does what it does
or if it is required) has some magic writes to "improve" serial signal
quality. I left them out as my HDD was detected with and without them.

Now, if we find that they are required, we have to find a way to make
the PHY driver know about the PHY revision. We'd usually add a
different compatible and deal with it accordingly.

So, not adding the compatible now _may_ just postpone a follow-up patch
for the different PHY setup of BG2 and render the new phy_base property
basically useless.

If you are just unhappy with the "static u32 bg2q_sata_phy_base"
assigned to of_device_id.data, I can convert that to Felipe's proposal.

Sebastian
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