linux-kernel - Re: [PATCH 1/4] phy: Add provision for calibrating phy.

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Message-ID: <CAFp+6iH697pP9UWhYLKJc_S2VZUJQ3y6GDzg78gat=X1kybtiQ@mail.gmail.com>
Date:	Wed, 9 Jul 2014 14:32:35 +0530
From:	Vivek Gautam <gautam.vivek@...sung.com>
To:	Pratyush Anand <pratyush.anand@...com>
Cc:	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-samsung-soc@...r.kernel.org" 
	<linux-samsung-soc@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"kishon@...com" <kishon@...com>,
	"mathias.nyman@...el.com" <mathias.nyman@...el.com>,
	"jwerner@...omium.org" <jwerner@...omium.org>,
	"kgene.kim@...sung.com" <kgene.kim@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/4] phy: Add provision for calibrating phy.

Hi,


On Mon, Jun 9, 2014 at 9:19 AM, Pratyush Anand <pratyush.anand@...com> wrote:
> On Fri, Jun 06, 2014 at 08:12:12PM +0800, Vivek Gautam wrote:
>> Some PHY controllers may need to calibrate certain
>> PHY settings after initialization of the controller and
>> sometimes even after initializing the PHY-consumer too.
>> Add support for the same in order to let consumers do so in need.
>>
>> Signed-off-by: vivek Gautam <gautam.vivek@...sung.com>
>> ---
>>  drivers/phy/phy-core.c  |   36 ++++++++++++++++++++++++++++++++++++
>>  include/linux/phy/phy.h |    7 +++++++
>>  2 files changed, 43 insertions(+)
>>
>> diff --git a/drivers/phy/phy-core.c b/drivers/phy/phy-core.c
>> index 74d4346..92d31a3 100644
>> --- a/drivers/phy/phy-core.c
>> +++ b/drivers/phy/phy-core.c
>> @@ -376,6 +376,42 @@ int phy_power_off(struct phy *phy)
>>  EXPORT_SYMBOL_GPL(phy_power_off);
>>
>>  /**
>> + * phy_calibrate - calibrate a phy post initialization
>> + * @phy: Pointer to 'phy' from consumer
>> + *
>> + * For certain PHYs, it may be needed to calibrate few phy parameters
>> + * post initialization. The need to calibrate may arise after the
>
> For USB you may need to calibrate phy after each new connection. If
> so, why not to use already existing struct usb_phy's notify_connect.

The phy_calibrate will rather be a one time phenomenon.
On exynos atleast the case is : the phy settings for PIPE3 phy on DWC3
controller need to be
configured post hcd reset. so that we don't need to re-configure these
phy settings on every connect.

Moreover *there are certain devices* which need these PHY settings
even to show a connect-status-change.
So, it would rather be not useful to create a 'phy_notify_connect' API
in drivers/phy/ and use the same for this purpose.



-- 
Best Regards
Vivek Gautam
Samsung R&D Institute, Bangalore
India
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