Re: [PATCH v4 07/10] hw/arm: Hook up FSI module in AST2600

[Ninad Palsule <ninad@linux.ibm.com>]

Hello Cedric,

Thanks for the review.

On 9/11/23 07:43, Cédric Le Goater wrote:
> On 9/9/23 00:28, Ninad Palsule wrote:
>> This patchset introduces IBM's Flexible Service Interface(FSI).
>>
>> Time for some fun with inter-processor buses. FSI allows a service
>> processor access to the internal buses of a host POWER processor to
>> perform configuration or debugging.
>>
>> FSI has long existed in POWER processes and so comes with some baggage,
>> including how it has been integrated into the ASPEED SoC.
>>
>> Working backwards from the POWER processor, the fundamental pieces of
>> interest for the implementation are:
>>
>> 1. The Common FRU Access Macro (CFAM), an address space containing
>>     various "engines" that drive accesses on buses internal and external
>>     to the POWER chip. Examples include the SBEFIFO and I2C masters. The
>>     engines hang off of an internal Local Bus (LBUS) which is described
>>     by the CFAM configuration block.
>>
>> 2. The FSI slave: The slave is the terminal point of the FSI bus for
>>     FSI symbols addressed to it. Slaves can be cascaded off of one
>>     another. The slave's configuration registers appear in address space
>>     of the CFAM to which it is attached.
>>
>> 3. The FSI master: A controller in the platform service processor (e.g.
>>     BMC) driving CFAM engine accesses into the POWER chip. At the
>>     hardware level FSI is a bit-based protocol supporting synchronous 
>> and
>>     DMA-driven accesses of engines in a CFAM.
>>
>> 4. The On-Chip Peripheral Bus (OPB): A low-speed bus typically found in
>>     POWER processors. This now makes an appearance in the ASPEED SoC due
>>     to tight integration of the FSI master IP with the OPB, mainly the
>>     existence of an MMIO-mapping of the CFAM address straight onto a
>>     sub-region of the OPB address space.
>>
>> 5. An APB-to-OPB bridge enabling access to the OPB from the ARM core in
>>     the AST2600. Hardware limitations prevent the OPB from being 
>> directly
>>     mapped into APB, so all accesses are indirect through the bridge.
>>
>> The implementation appears as following in the qemu device tree:
>>
>>      (qemu) info qtree
>>      bus: main-system-bus
>>        type System
>>        ...
>>        dev: aspeed.apb2opb, id ""
>>          gpio-out "sysbus-irq" 1
>>          mmio 000000001e79b000/0000000000001000
>>          bus: opb.1
>>            type opb
>>            dev: fsi.master, id ""
>>              bus: fsi.bus.1
>>                type fsi.bus
>>                dev: cfam.config, id ""
>>                dev: cfam, id ""
>>                  bus: lbus.1
>>                    type lbus
>>                    dev: scratchpad, id ""
>>                      address = 0 (0x0)
>>          bus: opb.0
>>            type opb
>>            dev: fsi.master, id ""
>>              bus: fsi.bus.0
>>                type fsi.bus
>>                dev: cfam.config, id ""
>>                dev: cfam, id ""
>>                  bus: lbus.0
>>                    type lbus
>>                    dev: scratchpad, id ""
>>                      address = 0 (0x0)
>>
>> The LBUS is modelled to maintain the qdev bus hierarchy and to take
>> advantage of the object model to automatically generate the CFAM
>> configuration block. The configuration block presents engines in the
>> order they are attached to the CFAM's LBUS. Engine implementations
>> should subclass the LBusDevice and set the 'config' member of
>> LBusDeviceClass to match the engine's type.
>>
>> CFAM designs offer a lot of flexibility, for instance it is possible for
>> a CFAM to be simultaneously driven from multiple FSI links. The modeling
>> is not so complete; it's assumed that each CFAM is attached to a single
>> FSI slave (as a consequence the CFAM subclasses the FSI slave).
>>
>> As for FSI, its symbols and wire-protocol are not modelled at all. This
>> is not necessary to get FSI off the ground thanks to the mapping of the
>> CFAM address space onto the OPB address space - the models follow this
>> directly and map the CFAM memory region into the OPB's memory region.
>> Future work includes supporting more advanced accesses that drive the
>> FSI master directly rather than indirectly via the CFAM mapping, which
>> will require implementing the FSI state machine and methods for each of
>> the FSI symbols on the slave. Further down the track we can also look at
>> supporting the bitbanged SoftFSI drivers in Linux by extending the FSI
>> slave model to resolve sequences of GPIO IRQs into FSI symbols, and
>> calling the associated symbol method on the slave to map the access onto
>> the CFAM.
>>
>> Testing:
>>      Tested by reading cfam config address 0 on rainier machine type.
>>
>>      root@p10bmc:~# pdbg -a getcfam 0x0
>>      p0: 0x0 = 0xc0022d15
>>
>> Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
>> Signed-off-by: Cédric Le Goater <clg@kaod.org>
>> Signed-off-by: Ninad Palsule <ninad@linux.ibm.com>
>
> you might want to add a specific fsi realize routine if extra devices
> need to be realized at the board level.

yes, we need to handle that once we are ready to add more devices.

Thanks!

~Ninad

>
> Reviewed-by: Cédric Le Goater <clg@kaod.org>
>
> Thanks,
>
> C.
>
>
>> ---
>>   hw/arm/aspeed_ast2600.c     | 19 +++++++++++++++++++
>>   include/hw/arm/aspeed_soc.h |  4 ++++
>>   2 files changed, 23 insertions(+)
>>
>> diff --git a/hw/arm/aspeed_ast2600.c b/hw/arm/aspeed_ast2600.c
>> index a8b3a8065a..010c9cee8a 100644
>> --- a/hw/arm/aspeed_ast2600.c
>> +++ b/hw/arm/aspeed_ast2600.c
>> @@ -75,6 +75,8 @@ static const hwaddr aspeed_soc_ast2600_memmap[] = {
>>       [ASPEED_DEV_UART12]    = 0x1E790600,
>>       [ASPEED_DEV_UART13]    = 0x1E790700,
>>       [ASPEED_DEV_VUART]     = 0x1E787000,
>> +    [ASPEED_DEV_FSI1]      = 0x1E79B000,
>> +    [ASPEED_DEV_FSI2]      = 0x1E79B100,
>>       [ASPEED_DEV_I3C]       = 0x1E7A0000,
>>       [ASPEED_DEV_SDRAM]     = 0x80000000,
>>   };
>> @@ -132,6 +134,8 @@ static const int aspeed_soc_ast2600_irqmap[] = {
>>       [ASPEED_DEV_ETH4]      = 33,
>>       [ASPEED_DEV_KCS]       = 138,   /* 138 -> 142 */
>>       [ASPEED_DEV_DP]        = 62,
>> +    [ASPEED_DEV_FSI1]      = 100,
>> +    [ASPEED_DEV_FSI2]      = 101,
>>       [ASPEED_DEV_I3C]       = 102,   /* 102 -> 107 */
>>   };
>>   @@ -262,6 +266,10 @@ static void aspeed_soc_ast2600_init(Object *obj)
>>       object_initialize_child(obj, "emmc-boot-controller",
>>                               &s->emmc_boot_controller,
>>                               TYPE_UNIMPLEMENTED_DEVICE);
>> +
>> +    for (i = 0; i < ASPEED_FSI_NUM; i++) {
>> +        object_initialize_child(obj, "fsi[*]", &s->fsi[i], 
>> TYPE_ASPEED_APB2OPB);
>> +    }
>>   }
>>     /*
>> @@ -622,6 +630,17 @@ static void 
>> aspeed_soc_ast2600_realize(DeviceState *dev, Error **errp)
>>           return;
>>       }
>>       aspeed_mmio_map(s, SYS_BUS_DEVICE(&s->sbc), 0, 
>> sc->memmap[ASPEED_DEV_SBC]);
>> +
>> +    /* FSI */
>> +    for (i = 0; i < ASPEED_FSI_NUM; i++) {
>> +        if (!sysbus_realize(SYS_BUS_DEVICE(&s->fsi[i]), errp)) {
>> +            return;
>> +        }
>> +        aspeed_mmio_map(s, SYS_BUS_DEVICE(&s->fsi[i]), 0,
>> +                        sc->memmap[ASPEED_DEV_FSI1 + i]);
>> +        sysbus_connect_irq(SYS_BUS_DEVICE(&s->fsi[i]), 0,
>> +                           aspeed_soc_get_irq(s, ASPEED_DEV_FSI1 + i));
>> +    }
>>   }
>>     static void aspeed_soc_ast2600_class_init(ObjectClass *oc, void 
>> *data)
>> diff --git a/include/hw/arm/aspeed_soc.h b/include/hw/arm/aspeed_soc.h
>> index 8adff70072..db3ba3abc7 100644
>> --- a/include/hw/arm/aspeed_soc.h
>> +++ b/include/hw/arm/aspeed_soc.h
>> @@ -36,6 +36,7 @@
>>   #include "hw/misc/aspeed_lpc.h"
>>   #include "hw/misc/unimp.h"
>>   #include "hw/misc/aspeed_peci.h"
>> +#include "hw/fsi/aspeed-apb2opb.h"
>>   #include "hw/char/serial.h"
>>     #define ASPEED_SPIS_NUM  2
>> @@ -96,6 +97,7 @@ struct AspeedSoCState {
>>       UnimplementedDeviceState udc;
>>       UnimplementedDeviceState sgpiom;
>>       UnimplementedDeviceState jtag[ASPEED_JTAG_NUM];
>> +    AspeedAPB2OPBState fsi[2];
>>   };
>>     #define TYPE_ASPEED_SOC "aspeed-soc"
>> @@ -191,6 +193,8 @@ enum {
>>       ASPEED_DEV_SGPIOM,
>>       ASPEED_DEV_JTAG0,
>>       ASPEED_DEV_JTAG1,
>> +    ASPEED_DEV_FSI1,
>> +    ASPEED_DEV_FSI2,
>>   };
>>     #define ASPEED_SOC_SPI_BOOT_ADDR 0x0
>