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

[Srinivas Kandagatla]

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@xxxxxxxxxx>
> > ---
> > Â drivers/soundwire/bus.cÂÂ |Â 2 ++
> > Â drivers/soundwire/bus.hÂÂ |Â 1 +
> > Â drivers/soundwire/slave.c | 52 +++++++++++++++++++++++++++++++++++++++
> > Â 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)
> > ÂÂÂÂÂÂ */
> > ÂÂÂÂÂ if (IS_ENABLED(CONFIG_ACPI) && ACPI_HANDLE(bus->dev))
> > ÂÂÂÂÂÂÂÂÂ ret = sdw_acpi_find_slaves(bus);
> > +ÂÂÂ else if (IS_ENABLED(CONFIG_OF) && bus->dev->of_node)
> > +ÂÂÂÂÂÂÂ ret = sdw_of_find_slaves(bus);
> > ÂÂÂÂÂ else
> > ÂÂÂÂÂÂÂÂÂ 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)
> > Â }
> > Â #endif
> > +int sdw_of_find_slaves(struct sdw_bus *bus);
> > Â void sdw_extract_slave_id(struct sdw_bus *bus,
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ 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 @@
> > Â // Copyright(c) 2015-17 Intel Corporation.
> > Â #include <linux/acpi.h>
> > +#include <linux/of.h>
> > Â #include <linux/soundwire/sdw.h>
> > Â #include <linux/soundwire/sdw_type.h>
> > Â #include "bus.h"
> > @@ -35,6 +36,7 @@ static int sdw_slave_add(struct sdw_bus *bus,
> > ÂÂÂÂÂ slave->dev.release = sdw_slave_release;
> > ÂÂÂÂÂ slave->dev.bus = &sdw_bus_type;
> > +ÂÂÂ slave->dev.of_node = of_node_get(to_of_node(fwnode));
> > ÂÂÂÂÂ slave->bus = bus;
> > ÂÂÂÂÂ slave->status = SDW_SLAVE_UNATTACHED;
> > ÂÂÂÂÂ slave->dev_num = 0;
> > @@ -112,3 +114,53 @@ int sdw_acpi_find_slaves(struct sdw_bus *bus)
> > Â }
> > Â #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)
> > +{
> > +ÂÂÂ struct device *dev = bus->dev;
> > +ÂÂÂ struct device_node *node;
> > +
> > +ÂÂÂ for_each_child_of_node(bus->dev->of_node, node) {
> > +ÂÂÂÂÂÂÂ int link_id, sdw_version, ret, len;
> > +ÂÂÂÂÂÂÂ const char *compat = NULL;
> > +ÂÂÂÂÂÂÂ struct sdw_slave_id id;
> > +ÂÂÂÂÂÂÂ const __be32 *addr;
> > +
> > +ÂÂÂÂÂÂÂ compat = of_get_property(node, "compatible", NULL);
> > +ÂÂÂÂÂÂÂ if (!compat)
> > +ÂÂÂÂÂÂÂÂÂÂÂ continue;
> > +
> > +ÂÂÂÂÂÂÂ ret = sscanf(compat, "sdw%01x%04hx%04hx%02hhx", &sdw_version,
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ &id.mfg_id, &id.part_id, &id.class_id);
> > +
> > +ÂÂÂÂÂÂÂ if (ret != 4) {
> > +ÂÂÂÂÂÂÂÂÂÂÂ dev_err(dev, "Invalid compatible string found %s\n",
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ compat);
> > +ÂÂÂÂÂÂÂÂÂÂÂ continue;
> > +ÂÂÂÂÂÂÂ }
> > +
> > +ÂÂÂÂÂÂÂ addr = of_get_property(node, "reg", &len);
> > +ÂÂÂÂÂÂÂ if (!addr || (len < 2 * sizeof(u32))) {
> > +ÂÂÂÂÂÂÂÂÂÂÂ dev_err(dev, "Invalid Instance and Link ID\n");
> > +ÂÂÂÂÂÂÂÂÂÂÂ continue;
> > +ÂÂÂÂÂÂÂ }
> > +
> > +ÂÂÂÂÂÂÂ id.unique_id = be32_to_cpup(addr++);
> > +ÂÂÂÂÂÂÂ 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
> > +ÂÂÂÂÂÂÂ id.sdw_version = sdw_version;
> > +
> > +ÂÂÂÂÂÂÂ /* Check for link_id match */
> > +ÂÂÂÂÂÂÂ if (link_id != bus->link_id)
> > +ÂÂÂÂÂÂÂÂÂÂÂ continue;
> > +
> > +ÂÂÂÂÂÂÂ sdw_slave_add(bus, &id, of_fwnode_handle(node));
> > +ÂÂÂ }
> > +
> > +ÂÂÂ return 0;
> > +}