Re: [RFC PATCH 2/4] drivers/bus: Freescale Management Complex (fsl-mc) bus driver

[German Rivera]

Hi Arnd,

Thanks for your comments. My replies inline below.
Please let me know if there is anything else, before post a respin
of the patch series that addresses your comments.

Thanks,

German

On 08/16/2014 09:12 AM, Arnd Bergmann wrote:
> On Friday 15 August 2014 17:13:12 J. German Rivera wrote:
> > +struct fsl_mc_bus *fsl_mc_bus;
> > +EXPORT_SYMBOL(fsl_mc_bus);
>
> This does not look like something that should be exported.
> Or even better, kill this structure entirely and just pass around
> pointers to the fsl_mc_device so you can deal with multiple root
> instances.
Ok. I'll remove this global structure.

> > +static struct kmem_cache *mc_dev_cache;
> > +
> > +/**
> > + * fsl_mc_bus_match - device to driver matching callback
> > + * @dev: the MC object device structure to match against
> > + * @drv: the device driver to search for matching MC object device id
> > + * structures
> > + *
> > + * Returns 1 on success, 0 otherwise.
> > + */
> > +static int fsl_mc_bus_match(struct device *dev, struct device_driver *drv)
> > +{
> > +	const struct fsl_mc_device_match_id *id;
> > +	struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
> > +	struct fsl_mc_driver *mc_drv = to_fsl_mc_driver(drv);
> > +	bool found = false;
> > +
> > +	if (WARN_ON(mc_dev->magic != FSL_MC_DEVICE_MAGIC))
> > +		goto out;
> > +	if (WARN_ON(mc_drv->magic != FSL_MC_DRIVER_MAGIC))
> > +		goto out;
>
> We normally don't do this magic number matching, just remove these
> and rely on the compile-time checks.
Ok. I'll remove all the magic fields and their checking.

> > +struct bus_type fsl_mc_bus_type = {
> > +	.name = "fsl-mc",
> > +	.match = fsl_mc_bus_match,
> > +	.uevent = fsl_mc_bus_uevent,
> > +	.drv_groups = NULL,
> > +	.dev_groups = NULL,
> > +	.bus_groups = NULL,
> > +	.pm = NULL,
> > +};
> > +EXPORT_SYMBOL(fsl_mc_bus_type);
>
> No need to assign NULL members.
Ok. I'll removed them.

> Does it need to be exported to drivers? How about making it
> EXPORT_SYMBOL_GPL if it does?
Yes it needs to be accessed by another driver that will come in
a later patch series. I'll change it to EXPORT_SYMBOL_GPL()

> > +static int dprc_parse_dt_node(struct platform_device *pdev,
> > +			      phys_addr_t *mc_portal_phys_addr,
> > +			      uint32_t *mc_portal_size)
> > +{
> > +	struct resource res;
> > +	struct device_node *pdev_of_node = pdev->dev.of_node;
> > +	int error = -EINVAL;
> > +
> > +	error = of_address_to_resource(pdev_of_node, 0, &res);
> > +	if (error < 0) {
> > +		FSL_MC_ERROR(&pdev->dev,
> > +			     "of_address_to_resource() failed for %s\n",
> > +			     pdev_of_node->full_name);
> > +		goto out;
> > +	}
> > +
> > +	*mc_portal_phys_addr = res.start;
> > +	*mc_portal_size = resource_size(&res);
> > +	error = 0;
> > +out:
> > +	return error;
> > +}
>
> Why not just call of_address_to_resource in the caller?
Done.

> > +/**
> > + * __fsl_mc_driver_register - registers a child device driver with the
> > + * MC bus
> > + *
> > + * This function is implicitly invoked from the registration function of
> > + * fsl_mc device drivers, which is generated by the
> > + * module_fsl_mc_driver() macro.
> > + */
> > +int __fsl_mc_driver_register(struct fsl_mc_driver *mc_driver,
> > +			     struct module *owner)
> > +{
> > +	struct fsl_mc_device *root_mc_dev;
>
> Here the root_mc_dev variable isn't really used for much.
Removed.

> > +static int fsl_mc_device_get_mmio_regions(struct fsl_mc_device *mc_dev,
> > +					  struct fsl_mc_device *container_dev)
> > +{
> > +	int i;
> > +	int error;
> > +	struct fsl_mc_device_region *regions;
> > +	struct dprc_obj_desc *obj_desc = &mc_dev->obj_desc;
> > +	struct device *parent_dev = mc_dev->dev.parent;
> > +
> > +	regions = kmalloc_array(obj_desc->region_count,
> > +				sizeof(regions[0]), GFP_KERNEL);
>
> Better use 'struct resource' for the resources than make your own type.
Ok, I will remove struct fsl_mc_device_region and use struct resource 
instead.

> > +		mc_dev->icid = container_dev->icid;
> > +		mc_dev->dma_mask = 0xffffffff;	/* 32bit */
> > +		mc_dev->dev.dma_mask = &mc_dev->dma_mask;
>
> Is 32-bit DMA a fundamental limit of the bus?
No, there is not 32-bit DMA limitation for this bus.
Also,this dma_mask field is not currently being used. So, I'll remove it.

> > +
> > +static const struct of_device_id fsl_mc_bus_match_table[] = {
> > +	{.compatible = "fsl,qoriq-mc",},
> > +	{},
> > +};
>
> Please add a binding documentation for this device in Documentation/device-tree/
Yes, this is being added in the 'ARM64: Add support for FSL's LS2085A 
SoC' patch series, already posted for review.

> > +#define FSL_MC_MAGIC(_a, _b, _c, _d) \
> > +	(((uint32_t)(_a) << 24) | \
> > +	((uint32_t)(_b) << 16) | \
> > +	((uint32_t)(_c) << 8)  | \
> > +	(uint32_t)(_d))
>
> Can be dropped once you remove all the magic number matching
Done.

> > +/**
> > + * struct fsl_mc_device_region - MC object device MMIO region
> > + * @addr: base physical address
> > + * @size: size of the region in bytes
> > + */
> > +struct fsl_mc_device_region {
> > +	phys_addr_t paddr;
> > +	uint32_t size;
> > +};
>
> Can be removed when you move to 'struct resource'
Done.

> > +/**
> > + * struct fsl_mc_device - MC object device object
> > + * @magic: marker to verify identity of this structure
>
> remove
Removed all 'magic' fields

> > + * @flags: MC object device flags
> > + * @icid: Isolation context ID for the device
> > + * @mc_handle: MC handle for the corresponding MC object opened
> > + * @mc_io: Pointer to MC IO object assigned to this device or
> > + * NULL if none.
> > + * @driver: Pointer to the MC object device driver for this device
>
> Use container_of(&this->dev.driver, ...) instead
Removed redundant driver field.

> > + * @container: Pointer to the DPRC device that contains this MC object device
>
> Why are there two devices for this? Should this just use dev->parent instead?
You are right. Removed the container field. We can get the parent DPRC 
of a given dev, from its dev.parent field.

> > + * @dev_node: Node in the container's child list
>
> Same here: just use the device model's list management instead if you can,
> or explain why this is needed.
We still need to keep a per-bus list of child devices (devices contained 
in a given DPRC object). Unless I'm missing something,
I think the device model's list management links together all the 
devices of the same bus type. We are trying to follow a similar approach 
to the pci_dev/pci_bus structs.

> > + * @obj_desc: MC description of the DPAA device
> > + * @num_regions: Number of MMIO regions for this MC object device
>
> Doesn't actually exist?
No. Removed.

> > +#define FSL_MC_ERROR(_dev, _fmt, ...) \
> > +	do {								\
> > +		if ((_dev) != NULL)					\
> > +			dev_err(_dev, "%s:" __stringify(__LINE__) " "   \
> > +				_fmt, __func__, ##__VA_ARGS__);		\
> > +		else							\
> > +			pr_err("%s:" __stringify(__LINE__) " " _fmt,	\
> > +			       __func__, ##__VA_ARGS__);		\
> > +	} while (0)
>
> just use dev_err() directly, it handles the !_dev case already
Done.

> > +/**
> > + * struct fsl_mc_bus - Management Complex (MC) bus object
> > + * @magic: marker to verify identity of this structure
> > + * @pdev: platform device for this MC bus object
> > + * @root_mc_dev: pointer to root MC object device for this MC bus.
> > + */
> > +struct fsl_mc_bus {
> > +#	define FSL_MC_BUS_MAGIC   FSL_MC_MAGIC('L', 'B', 'U', 'S')
> > +	uint32_t magic;
> > +	struct platform_device *pdev;
> > +	struct fsl_mc_device *root_mc_dev;
> > +};
>
> pdev should be root_mc_dev->dev->parent, and magic seems pointless, so
> no need for this structure at all.
Agreed. This is redundant. Removed.

> > +/**
> > + * struct fsl_mc_dprc - Data Path Resource Container (DPRC) object
> > + * @magic: marker to verify identity of this structure
> > + * @mc_dev: pointer to MC object device object for this DPRC
> > + * @mutex: mutex to serialize access to the container.
> > + * @child_device_count: have the count of devices in this DPRC
> > + * @child_list:	anchor node of list of child devices on this DPRC
> > + */
> > +struct fsl_mc_dprc {
> > +#	define FSL_MC_DPRC_MAGIC   FSL_MC_MAGIC('D', 'P', 'R', 'C')
> > +	uint32_t magic;
> > +	struct fsl_mc_device *mc_dev;
> > +	struct mutex mutex;	/* serializes access to fields below */
> > +	uint16_t child_device_count;	/* Count of devices in this DPRC */
> > +	struct list_head child_list;
> > +};
>
> It's not clear what this represents to me. mc_dev presumably already
> has a list of children, so why not just use a pointer to mc_dev
> and remove this structure entirely?
This structure represents the per-bus (per DPRC object) information.
It is kind of the equivalent to 'struct pci_bus' in the PCI world.
I have renamed this struct to 'struct fsl_mc_bus'.

> 	Arnd
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