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hw/i2c: support multiple masters

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Allow slaves to master the bus by registering a bottom halve. If the bus
is busy, the bottom half is queued up. When a slave has succesfully
mastered the bus, the bottom half is scheduled.

Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
[ clg : - fixed typos in commit log ]
Message-Id: <20220601210831.67259-4-its@irrelevant.dk>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20220630045133.32251-5-me@pjd.dev>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
This commit is contained in:
Klaus Jensen 2022-06-30 09:21:14 +02:00 committed by Cédric Le Goater
parent 0c0f1bee6a
commit 37fa5ca426
2 changed files with 47 additions and 1 deletions
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34
hw/i2c/core.c
View File

@ -13,6 +13,7 @@
#include "migration/vmstate.h"
#include "qapi/error.h"
#include "qemu/module.h"
#include "qemu/main-loop.h"
#include "trace.h"
#define I2C_BROADCAST 0x00
@ -62,6 +63,7 @@ I2CBus *i2c_init_bus(DeviceState *parent, const char *name)
bus = I2C_BUS(qbus_new(TYPE_I2C_BUS, parent, name));
QLIST_INIT(&bus->current_devs);
QSIMPLEQ_INIT(&bus->pending_masters);
vmstate_register(NULL, VMSTATE_INSTANCE_ID_ANY, &vmstate_i2c_bus, bus);
return bus;
}
@ -74,7 +76,7 @@ void i2c_slave_set_address(I2CSlave *dev, uint8_t address)
/* Return nonzero if bus is busy. */
int i2c_bus_busy(I2CBus *bus)
{
return !QLIST_EMPTY(&bus->current_devs);
return !QLIST_EMPTY(&bus->current_devs) || bus->bh;
}
bool i2c_scan_bus(I2CBus *bus, uint8_t address, bool broadcast,
@ -180,6 +182,26 @@ int i2c_start_transfer(I2CBus *bus, uint8_t address, bool is_recv)
: I2C_START_SEND);
}
void i2c_bus_master(I2CBus *bus, QEMUBH *bh)
{
if (i2c_bus_busy(bus)) {
I2CPendingMaster *node = g_new(struct I2CPendingMaster, 1);
node->bh = bh;
QSIMPLEQ_INSERT_TAIL(&bus->pending_masters, node, entry);
return;
}
bus->bh = bh;
qemu_bh_schedule(bus->bh);
}
void i2c_bus_release(I2CBus *bus)
{
bus->bh = NULL;
}
int i2c_start_recv(I2CBus *bus, uint8_t address)
{
return i2c_do_start_transfer(bus, address, I2C_START_RECV);
@ -206,6 +228,16 @@ void i2c_end_transfer(I2CBus *bus)
g_free(node);
}
bus->broadcast = false;
if (!QSIMPLEQ_EMPTY(&bus->pending_masters)) {
I2CPendingMaster *node = QSIMPLEQ_FIRST(&bus->pending_masters);
bus->bh = node->bh;
QSIMPLEQ_REMOVE_HEAD(&bus->pending_masters, entry);
g_free(node);
qemu_bh_schedule(bus->bh);
}
}
int i2c_send(I2CBus *bus, uint8_t data)

14
include/hw/i2c/i2c.h
View File

@ -69,13 +69,25 @@ struct I2CNode {
QLIST_ENTRY(I2CNode) next;
};
typedef struct I2CPendingMaster I2CPendingMaster;
struct I2CPendingMaster {
QEMUBH *bh;
QSIMPLEQ_ENTRY(I2CPendingMaster) entry;
};
typedef QLIST_HEAD(I2CNodeList, I2CNode) I2CNodeList;
typedef QSIMPLEQ_HEAD(I2CPendingMasters, I2CPendingMaster) I2CPendingMasters;
struct I2CBus {
BusState qbus;
I2CNodeList current_devs;
I2CPendingMasters pending_masters;
uint8_t saved_address;
bool broadcast;
/* Set from slave currently mastering the bus. */
QEMUBH *bh;
};
I2CBus *i2c_init_bus(DeviceState *parent, const char *name);
@ -117,6 +129,8 @@ int i2c_start_send(I2CBus *bus, uint8_t address);
void i2c_end_transfer(I2CBus *bus);
void i2c_nack(I2CBus *bus);
void i2c_bus_master(I2CBus *bus, QEMUBH *bh);
void i2c_bus_release(I2CBus *bus);
int i2c_send(I2CBus *bus, uint8_t data);
uint8_t i2c_recv(I2CBus *bus);
bool i2c_scan_bus(I2CBus *bus, uint8_t address, bool broadcast,