Re: [RFC PATCH v2 1/5] mfd: qpnp: add support for Qualcomm QPNP PMICs

[Stanimir Varbanov <svarbanov@mm-sol.com>]

Hi,

+Rob

Rob I used your old email, sorry about that.

<snip>

>>>> The Qualcomm QPNP PMIC chips are components used with the
>>>> Snapdragon 800 series SoC family.  This driver exists
>>>> largely as a glue mfd component, it exists to be an owner
>>>> of an SPMI regmap for children devices described in
>>>> device tree.
>>>>
>>>> Signed-off-by: Josh Cartwright <joshc@codeaurora.org>
>>>> Signed-off-by: Stanimir Varbanov <svarbanov@mm-sol.com>
>>>> ---
>>>>  drivers/mfd/Kconfig     |   15 ++++++
>>>>  drivers/mfd/Makefile    |    1 +
>>>>  drivers/mfd/qpnp-spmi.c |  129 +++++++++++++++++++++++++++++++++++++++++++++++
>>>>  3 files changed, 145 insertions(+), 0 deletions(-)
>>>>  create mode 100644 drivers/mfd/qpnp-spmi.c
>>>>
>>>> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
>>>> index ee8204c..258b733 100644
>>>> --- a/drivers/mfd/Kconfig
>>>> +++ b/drivers/mfd/Kconfig
>>>> @@ -524,6 +524,21 @@ config MFD_PM8921_CORE
>>>>  	  Say M here if you want to include support for PM8921 chip as a module.
>>>>  	  This will build a module called "pm8921-core".
>>>>  
>>>> +config MFD_QPNP_SPMI
>>>> +	tristate "Qualcomm QPNP SPMI PMIC"
>>>> +	depends on ARCH_QCOM || COMPILE_TEST
>>>> +	depends on OF
>>>> +	select MFD_CORE
>>>> +	select REGMAP_SPMI
>>>> +	help
>>>> +	  This enables support for the Qualcomm QPNP SPMI PMICs.
>>>> +	  These PMICs are currently used with the Snapdragon 800 series of
>>>> +	  SoCs.  Note, that this will only be useful paired with descriptions
>>>> +	  of the independent functions as children nodes in the device tree.
>>>

<snip>

>>>
>>>> + * This program is distributed in the hope that it will be useful,
>>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>>> + * GNU General Public License for more details.
>>>> + */
>>>> +#include <linux/kernel.h>
>>>> +#include <linux/module.h>
>>>> +#include <linux/spmi.h>
>>>> +#include <linux/regmap.h>
>>>> +#include <linux/of_address.h>
>>>> +#include <linux/slab.h>
>>>> +#include <linux/mfd/core.h>
>>>> +
>>>> +#define QPNP_RESOURCE_SIZE	256
>>>> +
>>>> +static const struct regmap_config qpnp_regmap_config = {
>>>> +	.reg_bits	= 16,
>>>> +	.val_bits	= 8,
>>>> +	.max_register	= 0xffff,
>>>> +};
>>>> +
>>>> +static int qpnp_index_to_resource(struct device_node *np, int index,
>>>> +				  struct resource *res)
>>>> +{
>>>> +	const char *name = NULL;
>>>> +	const __be32 *addrp;
>>>> +	u64 addr;
>>>> +
>>>> +	addrp = of_get_address(np, index, NULL, NULL);
>>>> +	if (!addrp)
>>>> +		return -EINVAL;
>>>> +
>>>> +	addr = of_read_number(addrp, 1);
>>>> +	if (addr == OF_BAD_ADDR)
>>>> +		return -EINVAL;
>>>> +
>>>> +	of_property_read_string_index(np, "reg-names", index, &name);
>>>> +
>>>> +	res->start = addr;
>>>> +	res->end = addr + QPNP_RESOURCE_SIZE - 1;
>>>> +	res->flags = IORESOURCE_REG;
>>>> +	res->name = name ? name : np->name;
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static int qpnp_add_device(struct spmi_device *root, struct device_node *child)
>>>> +{
>>>> +	struct mfd_cell cell = {};
>>>> +	struct resource *res, *r;
>>>> +	int num_resources = 0;
>>>> +	const char *compat;
>>>> +	int ret, i;
>>>> +
>>>> +	compat = of_get_property(child, "compatible", NULL);
>>>> +	if (!compat)
>>>> +		return -ENODEV;
>>>> +
>>>> +	while (of_get_address(child, num_resources, NULL, NULL))
>>>> +		num_resources++;
>>>> +
>>>> +	if (!num_resources)
>>>> +		return -ENODEV;
>>>> +
>>>> +	res = kcalloc(num_resources, sizeof(*res), GFP_KERNEL);
>>>> +	if (!res)
>>>> +		return -ENOMEM;
>>>> +
>>>> +	r = res;
>>>> +	for (i = 0; i < num_resources; i++, r++)
>>>> +		qpnp_index_to_resource(child, i, r);
>>>> +
>>>> +	cell.name = kasprintf(GFP_KERNEL, "%x.%04x.%s", root->usid,
>>>> +			      (u16)res[0].start, child->name);
>>>> +	cell.of_compatible = compat;
>>>> +	cell.num_resources = num_resources;
>>>> +	cell.resources = res;
>>>> +
>>>> +	ret = mfd_add_devices(&root->dev, PLATFORM_DEVID_NONE, &cell, 1,
>>>> +			      NULL, 0, NULL);
>>>> +
>>>> +	kfree(res);
>>>> +	kfree(cell.name);
>>>> +
>>>> +	return ret;
>>>> +}
>>>> +
>>>> +static int qpnp_probe(struct spmi_device *sdev)
>>>> +{
>>>> +	struct device_node *root = sdev->dev.of_node;
>>>> +	struct device_node *child;
>>>> +	struct regmap *regmap;
>>>> +
>>>> +	regmap = devm_regmap_init_spmi_ext(sdev, &qpnp_regmap_config);
>>>> +	if (IS_ERR(regmap))
>>>> +		return PTR_ERR(regmap);
>>>> +
>>>> +	for_each_available_child_of_node(root, child)
>>>> +		qpnp_add_device(sdev, child);
>>>
>>> This entire driver looks like a re-write of of_platform_populate().
>>>
>>> Why?
>>
>> of_platform_populate is not used because the PMIC function resources are
>> non-translatable. You can see that the resources are of type
>> IORESOURCE_REG (qpnp_index_to_resource()) not IORESOURCE_MEM or _IO.
>>
>> The whole point of this mfd driver is to parse devicetree to prepare
>> resources for every child and create platform device for it through
>> mfd_add_devices(). Then the PMIC function driver got its resources and
>> use them as register addresses passed to regmap. These register accesses
>> hits the SPMI controller which is the physical interface between PMIC's
>> and SoC.
> 
> I can't help but think that if this is required, it should be part of
> the core OF code, rather than doing your own thing which looks
> frighteningly like existing framework functionality.

Lee,

does it make sense to have a common of_mfd code for devicetree parsing?
Is that discussed already? I mean presently the mfd_cell resources and
number of resources are passed by the mfd_add_devices users. Is it
possible to have common code which parses devicetree sub-nodes of the
parent device_node and fill resources/create platform devices for them.


Rob, Grant I hope you guys have something to say here?


> 
> Either way, I'm going to need a DT Ack before I accept this.
> 

Sure.

-- 
regards,
Stan