SOC: Zedboard: Driver question

[amit mehta]

On Thu, Jun 12, 2014 at 4:52 PM, priyaranjan <priyaranjan45678 at gmail.com> wrote:
>
>
>
> On Thu, Jun 12, 2014 at 7:09 PM, amit mehta <gmate.amit at gmail.com> wrote:
>>
>> We are working on a school project in which we are trying to develop a
>> audio mixer
>> on Zedboard (Development board from Digilent). We have developed the IP
>> and have
>> integrated it with the overall hardware using Programmable logic. This
>> board has ARM
>> core. We have a Digilent pre-configured Linux source which we
>> cross-compiled
>> for ARM board, device tree blob and bootloader for Zync(BOOT.BIN). The
>> system
>> boots fine with Linux, but now to expose the recently added hardware
>> implementation
>> of audio mixer, we are trying to develop the driver using the platform
>> driver API.
>> Currently, In our reconfigurable hardware, we have 2 channels and a mixer
>> and we
>> want to access those individually as some file nodes under /proc FS. The
>> sample
>> code is shown below:
>>
>> <snip from myiir.c>
>> /* device match table to match with device node in device tree
>>  * These are the list of devices that we want to expose as platform device
>>  */
>> static const struct of_device_id myiir_of_match[] __devinitconst = {
>>         {.compatible = "dglnt,myiir-audio-ch0"},
>>         {.compatible = "dglnt,myiir-audio-ch1"},
>>         {.compatible = "dglnt,myiir-audio-mix0"},
>>         {},
>> };
>>
>> MODULE_DEVICE_TABLE(of, myiir_of_match);
>>
>> /* platform driver structure for myiir driver */
>> static struct platform_driver myiir_driver = {
>>         .driver = {
>>                 .name = DRIVER_NAME,
>>                 .owner = THIS_MODULE,
>>                 .of_match_table = myiir_of_match},
>>         .probe = myiir_probe,
>>         .remove = __devexit_p(myiir_remove),
>>         .shutdown = __devexit_p(myiir_shutdown)
>> };
>>
>> /* Register myiir platform driver */
>> module_platform_driver(myiir_driver);
>> <myiir.c>
>>
>> Now, inside the probe routine (myiir_probe), can we create proc
>> entries by calling
>> create_proc for each of these nodes and setting the appropriate read and
>> write
>> methods(file_operations) ?
>
>
>
> Yes, I feel this is fine, the proc entries to be created in probe,
> Initialize all data structures as required in probe.
>
Thank you for this confirmation. I've one more query regarding the
IO addresses. The CAD tool from Xilinx shows the base addresses
of our custom IP, which we have put into the device tree blob(also
shown in the attached screeshot) and in our driver, we are requesting
the memory region and after calling the ioremap, we access those
IO addresses, but is there are need to write the register addresses
in the device tree file in a particular order(asceding/descending) ?
<snip from device tree file>
                myiir-aud-ch0 {
                        compatible = "dglnt,myiir-audio-ch0";
                        reg = <0x74200000 0x10000>;
                };
                myiir-aud-ch1 {
                        compatible = "dglnt,myiir-audio-ch1";
                        reg = <0x74220000 0x10000>;
                };
                myiir-aud-mix0 {
                        compatible = "dglnt,myiir-audio-mix0";
                        reg = <0x68600000 0x10000>;
                };
<snip from device tree file>
The sequence of operation in probe routine is:

platform_get_resource(pdev, IORESOURCE_MEM, 0);
remap_size = res->end - res->start + 1;
request_mem_region(res->start, remap_size, pdev->name);
base_addr = ioremap(res->start, remap_size);

Thanks,
Kumar
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