netdev - Re: [PATCH v2 0/2] net: ethernet: ti: cpsw: delete rx

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Date:	Wed, 8 Jun 2016 17:06:08 +0300
From:	Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
To:	Schuyler Patton <spatton@...com>, mugunthanvnm@...com,
	linux-kernel@...r.kernel.org
Cc:	grygorii.strashko@...com, linux-omap@...r.kernel.org,
	netdev@...r.kernel.org, robh+dt@...nel.org, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, bcousson@...libre.com, tony@...mide.com,
	devicetree@...r.kernel.org
Subject: Re: [PATCH v2 0/2] net: ethernet: ti: cpsw: delete rx_descs property



On 08.06.16 17:01, Ivan Khoronzhuk wrote:
> Hi Schuyer,
>
> On 07.06.16 18:26, Schuyler Patton wrote:
>> Hi,
>>
>> On 06/07/2016 08:59 AM, Ivan Khoronzhuk wrote:
>>> There is no reason in rx_descs property because davinici_cpdma
>>> driver splits pool of descriptors equally between tx and rx channels.
>>> So, this patch series makes driver to use available number of
>>> descriptors for rx channels.
>>
>> I agree with the idea of consolidating how the descriptors are defined because of
>> the two variable components, number and size of the pool can be confusing to
>> end users. I would like to request to change how it is being proposed here.
>>
>> I think the number of descriptors should be left in the device tree source file as
>> is and remove the BD size variable and have the driver calculate the size of the
>> pool necessary to support the descriptor request. From an user perspective it is
>> easier I think to be able to list the number of descriptors necessary vs. the size
>> of the pool.
>>
>> Since the patch series points out how it is used so in the driver so to make that
>> consistent is perhaps change rx_descs to total_descs.
>>
>> Regards,
>> Schuyler
>
> The DT entry for cpsw doesn't have property for size of the pool.
> It contains only BD ram size, if you mean this. The size of the pool is
> software decision. Current version of DT entry contain only rx desc number.
> That is not correct, as it depends on the size of the descriptor, which is also
> h/w parameter. The DT entry has to describe only h/w part and shouldn't contain
> driver implementation details, and I'm looking on it from this perspective.
>
> Besides, rx_descs describes only rx number of descriptors, that are taken from
> the same pool as tx descriptors, and setting rx desc to some new value doesn't
> mean that rest of them are freed for tx. Also, I'm going to send series that
> adds multi channel support to the driver, and in this case, splitting of the
> pool will be more sophisticated than now, after what setting those parameters
> for user (he should do this via device tree) can be even more confusing. But,
should -> shouldn't

> as it's supposed, it's software decision that shouldn't leak to the DT.
>
>
>>>
>>> Based on master branch
>>>
>>> Since v1:
>>> - separate device tree and driver patches
>>> - return number of rx buffers from cpdma driver
>>>
>>> Ivan Khoronzhuk (2):
>>>    net: ethernet: ti: cpsw: remove rx_descs property
>>>    Documentation: DT: cpsw: remove rx_descs property
>>>
>>>   Documentation/devicetree/bindings/net/cpsw.txt |  1 -
>>>   arch/arm/boot/dts/am33xx.dtsi                  |  1 -
>>>   arch/arm/boot/dts/am4372.dtsi                  |  1 -
>>>   arch/arm/boot/dts/dm814x.dtsi                  |  1 -
>>>   arch/arm/boot/dts/dra7.dtsi                    |  1 -
>>>   drivers/net/ethernet/ti/cpsw.c                 | 13 +++----------
>>>   drivers/net/ethernet/ti/cpsw.h                 |  1 -
>>>   drivers/net/ethernet/ti/davinci_cpdma.c        |  6 ++++++
>>>   drivers/net/ethernet/ti/davinci_cpdma.h        |  1 +
>>>   9 files changed, 10 insertions(+), 16 deletions(-)
>>>
>>
>

-- 
Regards,
Ivan Khoronzhuk