Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [PATCH v4 3/5] i2c: designware: Add slave definitions | From | Luis Oliveira <> | Date | Thu, 22 Dec 2016 14:59:07 +0000 |
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On 13-Dec-16 14:11, Rob Herring wrote: > Again, please don't top post. And your line wrapping is messed up. > IOW, you can't use Outlook. > > On Tue, Dec 13, 2016 at 4:50 AM, Luis de Oliveira > <Luis.Oliveira@synopsys.com> wrote: >> The controller for i2c-designware cannot be slave/master at the same time and it has to be enabled knowing beforehand if we want it to be slave or master by something outside of the controller itself. >> >> I as looking and I see the use of this I2C_OWN_SLAVE_ADDRESS with the "linux,slave-24c02" slave interface but I am not seeing how it will help me identify a selected i2c-designware block as a "slave" device before instantiation. I'm sorry if I'm not understanding properly. >> I use the "linux,slave-24c02" to instantiate the i2c-designware as a slave with an address so I can do write/read operations, it is how I tested it. > > Something like this: > > of_for_each_child_node(child) { > of_property_read_u32(child, "reg", ®); > if (reg & I2C_OWN_SLAVE_ADDRESS)) > im_a_slave = true; > } > > ...rather than testing "mode" is equal to "slave". > > Rob >
Hi Rob, Andy,
I'm struggling to implement your suggestion @Rob. I checked the tegra124-jetson-tk1.dts that uses that approach but I have some doubts.
My DT is as follows
i2c@0x2000 { compatible = "snps,designware-i2c"; reg = <0x2000 0x100>; clock-frequency = <400000>; clocks = <&i2cclk>; interrupts = <0>;
I could add something like this:
eeprom@64 { compatible = "linux,slave-24c02"; reg = <(I2C_OWN_SLAVE_ADDRESS | 0x64)>; }
But I think this is different form what I was doing before. I have two questions:
- This way the I2C controller is identified as a slave controller or just the subnode eeprom? - This way looks like my slave address will be fixed
In the previous Patch v3 submission @Andy suggested a property that selects mode that I did and it's working. And you @Rob suggested to do it a common property. It is implemented in the DT like:
mode = "slave";
So before I do this changes can you please agree both if you still think this is the best approach?
Thank you both for your time, Luis
>> >> Luis >> >> -----Original Message----- >> From: Rob Herring [mailto:robh@kernel.org] >> Sent: Monday, December 12, 2016 23:16 >> To: Luis de Oliveira <Luis.Oliveira@synopsys.com> >> Cc: wsa@the-dreams.de; mark.rutland@arm.com; jarkko.nikula@linux.intel.com; andriy.shevchenko@linux.intel.com; mika.westerberg@linux.intel.com; linux-i2c@vger.kernel.org; devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; Ramiro.Oliveira@synopsys.com; Joao.Pinto@synopsys.com; CARLOS.PALMINHA@synopsys.com >> Subject: Re: [PATCH v4 3/5] i2c: designware: Add slave definitions >> >> On Mon, Dec 12, 2016 at 12:35 PM, Luis de Oliveira <Luis.Oliveira@synopsys.com> wrote: >>> Hi all, >> >> Please don't top post. >> >>> >>> The slave address could be set by the I2C slave backend so I can't use it to setup the controller. >>> A boolean property was my initial approach then Andy and Wolfram Sang suggested the use of compatible strings and later It was suggested to use a property to select mode but I can do it again if it's the best way. >>> Can you please tell me where should it be documented? >> >> bindings/i2c/i2c.txt. >> >> Actually, looking at this some more, we already have a way to describe the controller being a slave device with the I2C_OWN_SLAVE_ADDRESS flag in the reg property. We should just need a helper to read reg property of each child and check for the bit set. >> >> Rob
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