Re: [PATCH v2 04/13] hw/i2c: support multiple masters

[Cédric Le Goater]

Corey,

On 6/29/22 05:36, Peter Delevoryas wrote:
> From: Klaus Jensen <k.jensen@samsung.com>
>
> 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>
> ---

If it is OK with you, I plan to include this I2C extension in the
next Aspeed PR.

Thanks,

C.

>   hw/i2c/core.c        | 34 +++++++++++++++++++++++++++++++++-
>   include/hw/i2c/i2c.h | 14 ++++++++++++++
>   2 files changed, 47 insertions(+), 1 deletion(-)
>
> diff --git a/hw/i2c/core.c b/hw/i2c/core.c
> index d0cb2d32fa..145dce6078 100644
> --- a/hw/i2c/core.c
> +++ b/hw/i2c/core.c
> @@ -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)
> diff --git a/include/hw/i2c/i2c.h b/include/hw/i2c/i2c.h
> index 5ca3b708c0..be8bb8b78a 100644
> --- a/include/hw/i2c/i2c.h
> +++ b/include/hw/i2c/i2c.h
> @@ -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,