Re: [alsa-devel] [RESEND PATCH v4 2/4] soundwire: core: add device tree support for slave devices

[Srinivas Kandagatla <srinivas.kandagatla@linaro.org>]

On 23/08/2019 16:44, Pierre-Louis Bossart wrote:
> 
> 
> On 8/22/19 6:37 PM, Srinivas Kandagatla wrote:
>> This patch adds support to parsing device tree based
>> SoundWire slave devices.
>>
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
>> ---
>>   drivers/soundwire/bus.c   |  2 ++
>>   drivers/soundwire/bus.h   |  1 +
>>   drivers/soundwire/slave.c | 52 +++++++++++++++++++++++++++++++++++++++
>>   3 files changed, 55 insertions(+)
>>
>> diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
>> index 49f64b2115b9..c2eaeb5c38ed 100644
>> --- a/drivers/soundwire/bus.c
>> +++ b/drivers/soundwire/bus.c
>> @@ -77,6 +77,8 @@ int sdw_add_bus_master(struct sdw_bus *bus)
>>        */
>>       if (IS_ENABLED(CONFIG_ACPI) && ACPI_HANDLE(bus->dev))
>>           ret = sdw_acpi_find_slaves(bus);
>> +    else if (IS_ENABLED(CONFIG_OF) && bus->dev->of_node)
>> +        ret = sdw_of_find_slaves(bus);
>>       else
>>           ret = -ENOTSUPP; /* No ACPI/DT so error out */
>> diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h
>> index 3048ca153f22..ee46befedbd1 100644
>> --- a/drivers/soundwire/bus.h
>> +++ b/drivers/soundwire/bus.h
>> @@ -15,6 +15,7 @@ static inline int sdw_acpi_find_slaves(struct 
>> sdw_bus *bus)
>>   }
>>   #endif
>> +int sdw_of_find_slaves(struct sdw_bus *bus);
>>   void sdw_extract_slave_id(struct sdw_bus *bus,
>>                 u64 addr, struct sdw_slave_id *id);
>> diff --git a/drivers/soundwire/slave.c b/drivers/soundwire/slave.c
>> index f39a5815e25d..3ef265d2ee89 100644
>> --- a/drivers/soundwire/slave.c
>> +++ b/drivers/soundwire/slave.c
>> @@ -2,6 +2,7 @@
>>   // Copyright(c) 2015-17 Intel Corporation.
>>   #include <linux/acpi.h>
>> +#include <linux/of.h>
>>   #include <linux/soundwire/sdw.h>
>>   #include <linux/soundwire/sdw_type.h>
>>   #include "bus.h"
>> @@ -35,6 +36,7 @@ static int sdw_slave_add(struct sdw_bus *bus,
>>       slave->dev.release = sdw_slave_release;
>>       slave->dev.bus = &sdw_bus_type;
>> +    slave->dev.of_node = of_node_get(to_of_node(fwnode));
>>       slave->bus = bus;
>>       slave->status = SDW_SLAVE_UNATTACHED;
>>       slave->dev_num = 0;
>> @@ -112,3 +114,53 @@ int sdw_acpi_find_slaves(struct sdw_bus *bus)
>>   }
>>   #endif
>> +
>> +/*
>> + * sdw_of_find_slaves() - Find Slave devices in master device tree node
>> + * @bus: SDW bus instance
>> + *
>> + * Scans Master DT node for SDW child Slave devices and registers it.
>> + */
>> +int sdw_of_find_slaves(struct sdw_bus *bus)
>> +{
>> +    struct device *dev = bus->dev;
>> +    struct device_node *node;
>> +
>> +    for_each_child_of_node(bus->dev->of_node, node) {
>> +        int link_id, sdw_version, ret, len;
>> +        const char *compat = NULL;
>> +        struct sdw_slave_id id;
>> +        const __be32 *addr;
>> +
>> +        compat = of_get_property(node, "compatible", NULL);
>> +        if (!compat)
>> +            continue;
>> +
>> +        ret = sscanf(compat, "sdw%01x%04hx%04hx%02hhx", &sdw_version,
>> +                 &id.mfg_id, &id.part_id, &id.class_id);
>> +
>> +        if (ret != 4) {
>> +            dev_err(dev, "Invalid compatible string found %s\n",
>> +                compat);
>> +            continue;
>> +        }
>> +
>> +        addr = of_get_property(node, "reg", &len);
>> +        if (!addr || (len < 2 * sizeof(u32))) {
>> +            dev_err(dev, "Invalid Instance and Link ID\n");
>> +            continue;
>> +        }
>> +
>> +        id.unique_id = be32_to_cpup(addr++);
>> +        link_id = be32_to_cpup(addr);
> 
> So here the link ID is obviously not in the address, so you are not 
> using the MIPI spec as we discussed initially?

No, Rob rejected that approach (https://lkml.org/lkml/2019/8/22/490) 
with the fact that compatible string should be constant for each instance.

--srini
> 
>> +        id.sdw_version = sdw_version;
>> +
>> +        /* Check for link_id match */
>> +        if (link_id != bus->link_id)
>> +            continue;
>> +
>> +        sdw_slave_add(bus, &id, of_fwnode_handle(node));
>> +    }
>> +
>> +    return 0;
>> +}
>>