Re: [PATCH V10 7/7] dma: qcom_hidma: add support for object hierarchy

Sinan Kaya
2015-12-30T15:28:30Z

On 12/19/2015 1:37 PM, Andy Shevchenko wrote:
> On Thu, Dec 17, 2015 at 7:01 PM, Sinan Kaya <okaya@codeaurora.org> wrote:
>> In order to create a relationship model between the channels and the
>> management object, we are adding support for object hierarchy to the
>> drivers. This patch simplifies the userspace application development.
>> We will not have to traverse different firmware paths based on device
>> tree or ACPI baed kernels.
>>
>> No matter what flavor of kernel is used, objects will be represented as
>> platform devices.
>>
>> The new layout is as follows:
>>
>> hidmam_10: hidma-mgmt@0x5A000000 {
>> compatible = "qcom,hidma-mgmt-1.0";
>> ...
>>
>> hidma_10: hidma@0x5a010000 {
>> compatible = "qcom,hidma-1.0";
>> ...
>> }
>> }
>>
>> The hidma_mgmt_init detects each instance of the hidma-mgmt-1.0 objects
>> in device tree and calls into the channel driver to create platform devices
>> for each child of the management object.
>>
>> Signed-off-by: Sinan Kaya <okaya@codeaurora.org>
>
>
>> +What: /sys/devices/platform/hidma-*/chid
>> + /sys/devices/platform/QCOM8061:*/chid
>> +Date: Dec 2015
>> +KernelVersion: 4.4
>> +Contact: "Sinan Kaya <okaya@cudeaurora.org>"
>> +Description:
>> + Contains the ID of the channel within the HIDMA instance.
>> + It is used to associate a given HIDMA channel with the
>> + priority and weight calls in the management interface.
>
>> -module_platform_driver(hidma_mgmt_driver);
>> +#ifdef CONFIG_OF
>> +static int object_counter;
>> +
>> +static int __init hidma_mgmt_of_populate_channels(struct device_node *np)
>> +{
>> + struct platform_device *pdev_parent = of_find_device_by_node(np);
>> + struct platform_device_info pdevinfo;
>> + struct of_phandle_args out_irq;
>> + struct device_node *child;
>> + struct resource *res;
>> + const __be32 *cell;
>
> Always BE ?

Yes, as Timur indicated device tree is big endian all the time.
>
>> + int ret = 0, size, i, num;
>> + u64 addr, addr_size;
>
> resource_size_t

These values are read from the device tree blob using of_read_number function. of_read_number
returns a u64.
>
>> +
>> + for_each_available_child_of_node(np, child) {
>> + int iter = 0;
>> +
>> + cell = of_get_property(child, "reg", &size);
>> + if (!cell) {
>> + ret = -EINVAL;
>> + goto out;
>> + }
>> +
>> + size /= (sizeof(*cell));
>
> Redundant parens. I think it might be good to use common sense for
> operator precedence, here is a radical example of ignoring it. And
> this is not the first case.

Removed. Note that I copied most of this function from another driver.

>
>> + num = size /
>> + (of_n_addr_cells(child) + of_n_size_cells(child)) + 1;
>> +
>> + /* allocate a resource array */
>> + res = kcalloc(num, sizeof(*res), GFP_KERNEL);
>> + if (!res) {
>> + ret = -ENOMEM;
>> + goto out;
>> + }
>> +
>> + /* read each reg value */
>> + i = 0;
>> + while (i < size) {
>> + addr = of_read_number(&cell[i],
>> + of_n_addr_cells(child));
>> + i += of_n_addr_cells(child);
>> +
>> + addr_size = of_read_number(&cell[i],
>> + of_n_size_cells(child));
>> + i += of_n_size_cells(child);
>> +
>> + res[iter].start = addr;
>> + res[iter].end = res[iter].start + addr_size - 1;
>> + res[iter].flags = IORESOURCE_MEM;
>
> res->start = …
> …
> res++;

ok

>
>> + iter++;
>> + }
>> +
>> + ret = of_irq_parse_one(child, 0, &out_irq);
>> + if (ret)
>> + goto out;
>> +
>> + res[iter].start = irq_create_of_mapping(&out_irq);
>> + res[iter].name = "hidma event irq";
>> + res[iter].flags = IORESOURCE_IRQ;
>
> Ditto.
ok

>
>> +
>> + pdevinfo.fwnode = &child->fwnode;
>> + pdevinfo.parent = pdev_parent ? &pdev_parent->dev : NULL;
>> + pdevinfo.name = child->name;
>> + pdevinfo.id = object_counter++;
>> + pdevinfo.res = res;
>> + pdevinfo.num_res = num;
>> + pdevinfo.data = NULL;
>> + pdevinfo.size_data = 0;
>> + pdevinfo.dma_mask = DMA_BIT_MASK(64);
>> + platform_device_register_full(&pdevinfo);
>> +
>> + kfree(res);
>> + res = NULL;
>> + }
>> +out:
>
>> + kfree(res);
>
>
>> +
>> + return ret;
>> +}
>> +#endif
>> +
>> +static int __init hidma_mgmt_init(void)
>> +{
>> +#ifdef CONFIG_OF
>> + struct device_node *child;
>> +
>> + for (child = of_find_matching_node(NULL, hidma_mgmt_match); child;
>> + child = of_find_matching_node(child, hidma_mgmt_match)) {
>> + /* device tree based firmware here */
>> + hidma_mgmt_of_populate_channels(child);
>> + of_node_put(child);
>> + }
>
> And why this is can't be done in probe of parent node driver?

The populate function creates platform objects using platform_device_register_full function above.
The hidma device driver later probes the object during object enumeration phase.

I tried moving platform_device_register_full into the probe context. The objects got generated but hidma
device driver didn't probe the object. I suppose we are required to create the objects before the probing starts.

I copied this pattern from another driver.

>
>> +#endif
>> + platform_driver_register(&hidma_mgmt_driver);
>> +
>> + return 0;
>> +}
>> +module_init(hidma_mgmt_init);
>

--
Sinan Kaya