[PATCH 2/3] i3c: master: Extend address status bit to 4 and add I3C_ADDR_SLOT_EXT_INIT

Frank Li
2024-10-01T18:16:34Z

Extend the address status bit to 4 and introduce the I3C_ADDR_SLOT_EXT_INIT
macro to indicate that a device prefers a specific address. This is
generally set by the 'assigned-address' in the device tree source (dts)
file.

┌────┬─────────────┬───┬─────────┬───┐
│S/Sr│ 7'h7E RnW=0 │ACK│ ENTDAA │ T ├────┐
└────┴─────────────┴───┴─────────┴───┘ │
┌─────────────────────────────────────────┘
│ ┌──┬─────────────┬───┬─────────────────┬────────────────┬───┬─────────┐
└─►│Sr│7'h7E RnW=1 │ACK│48bit UID BCR DCR│Assign 7bit Addr│PAR│ ACK/NACK│
└──┴─────────────┴───┴─────────────────┴────────────────┴───┴─────────┘

Some master controllers (such as HCI) need to prepare the entire above
transaction before sending it out to the I3C bus. This means that a 7-bit
dynamic address needs to be allocated before knowing the target device's
UID information.

However, some I3C targets want a specific address (called as
"init_dyn_addr"), which is typically specified by the DT's assigned-address
property. (Lower addresses have higher IBI priority, and the target can
adjust this by using the assigned-address property if using DT). The
function i3c_master_add_i3c_dev_locked() will switch to this
"init_dyn_addr" if it is not in use.

Therefore, i3c_bus_get_free_addr() should return a free address that has
not been claimed by any target devices as "init_dyn_addr" (indicated by
I3C_ADDR_SLOT_EXT_INIT). This allows the device with the "init_dyn_addr"
to switch to its "init_dyn_addr" when it hot-joins the I3C bus. Otherwise,
if the "init_dyn_addr" is already in use by another I3C device, the target
device will not be able to switch to its desired address.

If all of above address are already used, i3c_bus_get_free_addr() return
one from the claimed as init_dyn_addr and free address slot. This ensures
support devices as much as possible.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
change from v3 to v4
- rewrite commit message and comment for i3c_bus_get_free_addr()
---
drivers/i3c/master.c | 68 ++++++++++++++++++++++++++++++++++++++++------
include/linux/i3c/master.h | 7 +++--
2 files changed, 64 insertions(+), 11 deletions(-)

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index dcf8d23c5941a..a56cb281e6b6d 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -345,7 +345,7 @@ const struct bus_type i3c_bus_type = {
EXPORT_SYMBOL_GPL(i3c_bus_type);

static enum i3c_addr_slot_status
-i3c_bus_get_addr_slot_status(struct i3c_bus *bus, u16 addr)
+i3c_bus_get_addr_slot_status_ext(struct i3c_bus *bus, u16 addr)
{
unsigned long status;
int bitpos = addr * I3C_ADDR_SLOT_STATUS_BITS;
@@ -356,11 +356,17 @@ i3c_bus_get_addr_slot_status(struct i3c_bus *bus, u16 addr)
status = bus->addrslots[bitpos / BITS_PER_LONG];
status >>= bitpos % BITS_PER_LONG;

- return status & I3C_ADDR_SLOT_STATUS_MASK;
+ return status & I3C_ADDR_SLOT_EXT_STATUS_MASK;
}

-static void i3c_bus_set_addr_slot_status(struct i3c_bus *bus, u16 addr,
- enum i3c_addr_slot_status status)
+static enum i3c_addr_slot_status
+i3c_bus_get_addr_slot_status(struct i3c_bus *bus, u16 addr)
+{
+ return i3c_bus_get_addr_slot_status_ext(bus, addr) & I3C_ADDR_SLOT_STATUS_MASK;
+}
+
+static void i3c_bus_set_addr_slot_status_mask(struct i3c_bus *bus, u16 addr,
+ enum i3c_addr_slot_status status, int mask)
{
int bitpos = addr * I3C_ADDR_SLOT_STATUS_BITS;
unsigned long *ptr;
@@ -369,11 +375,22 @@ static void i3c_bus_set_addr_slot_status(struct i3c_bus *bus, u16 addr,
return;

ptr = bus->addrslots + (bitpos / BITS_PER_LONG);
- *ptr &= ~((unsigned long)I3C_ADDR_SLOT_STATUS_MASK <<
- (bitpos % BITS_PER_LONG));
+ *ptr &= ~((unsigned long)mask << (bitpos % BITS_PER_LONG));
*ptr |= (unsigned long)status << (bitpos % BITS_PER_LONG);
}

+static void i3c_bus_set_addr_slot_status(struct i3c_bus *bus, u16 addr,
+ enum i3c_addr_slot_status status)
+{
+ i3c_bus_set_addr_slot_status_mask(bus, addr, status, I3C_ADDR_SLOT_STATUS_MASK);
+}
+
+static void i3c_bus_set_addr_slot_status_ext(struct i3c_bus *bus, u16 addr,
+ enum i3c_addr_slot_status status)
+{
+ i3c_bus_set_addr_slot_status_mask(bus, addr, status, I3C_ADDR_SLOT_EXT_STATUS_MASK);
+}
+
static bool i3c_bus_dev_addr_is_avail(struct i3c_bus *bus, u8 addr)
{
enum i3c_addr_slot_status status;
@@ -383,11 +400,44 @@ static bool i3c_bus_dev_addr_is_avail(struct i3c_bus *bus, u8 addr)
return status == I3C_ADDR_SLOT_FREE;
}

+/*
+ * ┌────┬─────────────┬───┬─────────┬───┐
+ * │S/Sr│ 7'h7E RnW=0 │ACK│ ENTDAA │ T ├────┐
+ * └────┴─────────────┴───┴─────────┴───┘ │
+ * ┌─────────────────────────────────────────┘
+ * │ ┌──┬─────────────┬───┬─────────────────┬────────────────┬───┬─────────┐
+ * └─►│Sr│7'h7E RnW=1 │ACK│48bit UID BCR DCR│Assign 7bit Addr│PAR│ ACK/NACK│
+ * └──┴─────────────┴───┴─────────────────┴────────────────┴───┴─────────┘
+ * Some master controllers (such as HCI) need to prepare the entire above transaction before
+ * sending it out to the I3C bus. This means that a 7-bit dynamic address needs to be allocated
+ * before knowing the target device's UID information.
+ *
+ * However, some I3C targets want a specific address (called as "init_dyn_addr"), which is
+ * typically specified by the DT's assigned-address property. (Lower addresses have higher IBI
+ * priority, and the target can adjust this by using the assigned-address property if using DT).
+ * The function i3c_master_add_i3c_dev_locked() will switch to this "init_dyn_addr" if it is not
+ * in use.
+ *
+ * Therefore, i3c_bus_get_free_addr() should return a free address that has not been claimed by any
+ * target devices as "init_dyn_addr". This allows the device with the "init_dyn_addr" to switch to
+ * its "init_dyn_addr" when it hot-joins the I3C bus. Otherwise, if the "init_dyn_addr" is already
+ * in use by another I3C device, the target device will not be able to switch to its desired
+ * address.
+ *
+ * If all of above address are already used, i3c_bus_get_free_addr() return one from the claimed as
+ * init_dyn_addr and free address slot. This ensures support devices as much as possible.
+ */
static int i3c_bus_get_free_addr(struct i3c_bus *bus, u8 start_addr)
{
enum i3c_addr_slot_status status;
u8 addr;

+ for (addr = start_addr; addr < I3C_MAX_ADDR; addr++) {
+ status = i3c_bus_get_addr_slot_status_ext(bus, addr);
+ if (status == I3C_ADDR_SLOT_FREE)
+ return addr;
+ }
+
for (addr = start_addr; addr < I3C_MAX_ADDR; addr++) {
status = i3c_bus_get_addr_slot_status(bus, addr);
if (status == I3C_ADDR_SLOT_FREE)
@@ -1918,9 +1968,9 @@ static int i3c_master_bus_init(struct i3c_master_controller *master)
goto err_rstdaa;
}

- i3c_bus_set_addr_slot_status(&master->bus,
- i3cboardinfo->init_dyn_addr,
- I3C_ADDR_SLOT_I3C_DEV);
+ i3c_bus_set_addr_slot_status_ext(&master->bus,
+ i3cboardinfo->init_dyn_addr,
+ I3C_ADDR_SLOT_I3C_DEV | I3C_ADDR_SLOT_EXT_INIT);

/*
* Only try to create/attach devices that have a static
diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
index 2100547b2d8d2..57ad6044ac856 100644
--- a/include/linux/i3c/master.h
+++ b/include/linux/i3c/master.h
@@ -298,7 +298,8 @@ enum i3c_open_drain_speed {
* @I3C_ADDR_SLOT_I2C_DEV: address is assigned to an I2C device
* @I3C_ADDR_SLOT_I3C_DEV: address is assigned to an I3C device
* @I3C_ADDR_SLOT_STATUS_MASK: address slot mask
- *
+ * @I3C_ADDR_SLOT_EXT_INIT: the bitmask represents addresses that are preferred by some devices,
+ * such as the "assigned-address" property in a device tree source (DTS).
* On an I3C bus, addresses are assigned dynamically, and we need to know which
* addresses are free to use and which ones are already assigned.
*
@@ -311,9 +312,11 @@ enum i3c_addr_slot_status {
I3C_ADDR_SLOT_I2C_DEV,
I3C_ADDR_SLOT_I3C_DEV,
I3C_ADDR_SLOT_STATUS_MASK = 3,
+ I3C_ADDR_SLOT_EXT_STATUS_MASK = 7,
+ I3C_ADDR_SLOT_EXT_INIT = BIT(2),
};

-#define I3C_ADDR_SLOT_STATUS_BITS 2
+#define I3C_ADDR_SLOT_STATUS_BITS 4

/**
* struct i3c_bus - I3C bus object

--
2.34.1