Subject: Re: [RFC PATCH] drivers: ata: Read Rx water mark value from
 device-tree
To: Arnd Bergmann <arnd@arndb.de>, Michal Simek <michal.simek@xilinx.com>
References: <1455974302-7082-1-git-send-email-anuragku@xilinx.com>
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CC: Anurag Kumar Vulisha <anuragku@xilinx.com>, Rob Herring <robh@kernel.org>,
        =?UTF-8?Q?S=c3=b6ren_Brinkmann?= <soren.brinkmann@xilinx.com>,
        "pawel.moll@arm.com" <pawel.moll@arm.com>,
        "mark.rutland@arm.com" <mark.rutland@arm.com>,
        "ijc+devicetree@hellion.org.uk" <ijc+devicetree@hellion.org.uk>,
        "galak@codeaurora.org" <galak@codeaurora.org>,
        "tj@kernel.org" <tj@kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-ide@vger.kernel.org" <linux-ide@vger.kernel.org>,
        Anirudha Sarangi <anirudh@xilinx.com>,
        Srikanth Vemula <svemula@xilinx.com>,
        "Punnaiah Choudary Kalluri" <punnaia@xilinx.com>
From: Michal Simek <michal.simek@xilinx.com>
Message-ID: <56D6D3D0.9030408@xilinx.com>
Date: Wed, 2 Mar 2016 12:51:44 +0100
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On 2.3.2016 12:42, Arnd Bergmann wrote:
> On Wednesday 02 March 2016 10:27:51 Michal Simek wrote:
>>
>> No problem with default value in driver. Something has to be setup.
>> Reset value based on reg spec I was checking is 0x20. Based on our
>> testing we saw some issues that's why 0x40 was setup as default value.
>> There is a need to be able to configure this value for example for
>> testing different values that's why I think module parameter should be
>> the right way to go.
> 
> I don't object to the module parameter, but I don't understand how important
> that kind of testing is to normal users. Who would set it, aside from
> the person writing that driver to come up with the correct default?
> 
>> If this should be DT parameters there should be different ceva IP which
>> allows different fifo size and different watermark level to be setup by
>> user.
>>
>> What do you think? Does it sound reasonable.
> 
> Having a property for the actual hardware fifo size once you get
> different implementations seems like the correct approach, but it's
> moot as long as all implementations are hardwired to 128 entries.

yep right now and we don't know what can happen in future. I just wanted
to point to example where this property can be specified or wired to
particular compatible string.

Anurag: Please make it as module parameter instead of DT parameter.

Thanks,
Michal