Re: [PATCH v5 05/10] hw/fsi: IBM's On-chip Peripheral Bus

[Daniel P . Berrangé]

On Wed, Oct 11, 2023 at 10:13:34AM -0500, Ninad Palsule wrote:
> This is a part of patchset where IBM's Flexible Service Interface is
> introduced.
> 
> 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.
> 
> 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>
> Reviewed-by: Joel Stanley <joel@jms.id.au>
> ---
> v2:
> - Incorporated review comment by Joel.
> v5:
> - Incorporated review comments by Cedric.
> ---
>  include/hw/fsi/opb.h |  43 ++++++++++
>  hw/fsi/fsi-master.c  |   3 +-
>  hw/fsi/opb.c         | 185 +++++++++++++++++++++++++++++++++++++++++++
>  hw/fsi/Kconfig       |   4 +
>  hw/fsi/meson.build   |   1 +
>  hw/fsi/trace-events  |   2 +
>  6 files changed, 236 insertions(+), 2 deletions(-)
>  create mode 100644 include/hw/fsi/opb.h
>  create mode 100644 hw/fsi/opb.c
> 
> diff --git a/include/hw/fsi/opb.h b/include/hw/fsi/opb.h
> new file mode 100644
> index 0000000000..f8ce00383e
> --- /dev/null
> +++ b/include/hw/fsi/opb.h
> @@ -0,0 +1,43 @@
> +/*
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + * Copyright (C) 2023 IBM Corp.
> + *
> + * IBM On-Chip Peripheral Bus
> + */
> +#ifndef FSI_OPB_H
> +#define FSI_OPB_H
> +
> +#include "exec/memory.h"
> +#include "hw/fsi/fsi-master.h"
> +
> +#define TYPE_OP_BUS "opb"
> +OBJECT_DECLARE_SIMPLE_TYPE(OPBus, OP_BUS)
> +
> +typedef struct OPBus {
> +        /*< private >*/
> +        BusState bus;
> +
> +        /*< public >*/
> +        MemoryRegion mr;
> +        AddressSpace as;
> +
> +        /* Model OPB as dumb enough just to provide an address-space */
> +        /* TODO: Maybe don't store device state in the bus? */
> +        FSIMasterState fsi;
> +} OPBus;
> +
> +typedef struct OPBusClass {
> +        BusClass parent_class;
> +} OPBusClass;
> +
> +uint8_t opb_read8(OPBus *opb, hwaddr addr);
> +uint16_t opb_read16(OPBus *opb, hwaddr addr);
> +uint32_t opb_read32(OPBus *opb, hwaddr addr);
> +void opb_write8(OPBus *opb, hwaddr addr, uint8_t data);
> +void opb_write16(OPBus *opb, hwaddr addr, uint16_t data);
> +void opb_write32(OPBus *opb, hwaddr addr, uint32_t data);
> +
> +void opb_fsi_master_address(OPBus *opb, hwaddr addr);
> +void opb_opb2fsi_address(OPBus *opb, hwaddr addr);
> +
> +#endif /* FSI_OPB_H */
> diff --git a/hw/fsi/fsi-master.c b/hw/fsi/fsi-master.c
> index 8f4ae641c7..ede1a58e98 100644
> --- a/hw/fsi/fsi-master.c
> +++ b/hw/fsi/fsi-master.c
> @@ -11,8 +11,7 @@
>  #include "trace.h"
>  
>  #include "hw/fsi/fsi-master.h"
> -
> -#define TYPE_OP_BUS "opb"
> +#include "hw/fsi/opb.h"
>  
>  #define TO_REG(x)                               ((x) >> 2)
>  
> diff --git a/hw/fsi/opb.c b/hw/fsi/opb.c
> new file mode 100644
> index 0000000000..7ffd7730f7
> --- /dev/null
> +++ b/hw/fsi/opb.c
> @@ -0,0 +1,185 @@
> +/*
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + * Copyright (C) 2023 IBM Corp.
> + *
> + * IBM On-chip Peripheral Bus
> + */
> +
> +#include "qemu/osdep.h"
> +
> +#include "qapi/error.h"
> +#include "qemu/log.h"
> +#include "trace.h"
> +
> +#include "hw/fsi/opb.h"
> +
> +static MemTxResult opb_read(OPBus *opb, hwaddr addr, void *data, size_t len)
> +{
> +    MemTxResult tx;
> +    tx = address_space_read(&opb->as, addr, MEMTXATTRS_UNSPECIFIED, data,
> +                              len);
> +    if (tx) {
> +        qemu_log_mask(LOG_GUEST_ERROR,
> +                      "%s: OPB read failed: 0x%"HWADDR_PRIx" for %lu\n",
> +                      __func__, addr, len);
> +    }
> +    return tx;
> +}

Use a tracepoint rather than an always-on log

> +
> +uint8_t opb_read8(OPBus *opb, hwaddr addr)
> +{
> +    uint8_t data = -1;
> +
> +    (void)opb_read(opb, addr, &data, sizeof(data));
> +
> +    return data;
> +}
> +
> +uint16_t opb_read16(OPBus *opb, hwaddr addr)
> +{
> +    uint16_t data = -1;
> +
> +    (void)opb_read(opb, addr, &data, sizeof(data));
> +
> +    return data;
> +}
> +
> +uint32_t opb_read32(OPBus *opb, hwaddr addr)
> +{
> +    uint32_t data = -1;
> +
> +    (void)opb_read(opb, addr, &data, sizeof(data));
> +
> +    return data;
> +}
> +
> +static void opb_write(OPBus *opb, hwaddr addr, void *data, size_t len)
> +{
> +    MemTxResult tx;
> +    tx = address_space_write(&opb->as, addr, MEMTXATTRS_UNSPECIFIED, data,
> +                               len);
> +    if (tx) {
> +        qemu_log_mask(LOG_GUEST_ERROR,
> +                      "%s: OPB write failed: %"HWADDR_PRIx" for %lu\n",
> +                      __func__, addr, len);
> +    }
> +}

Again tracepoint


> +static void opb_realize(BusState *bus, Error **errp)
> +{
> +    OPBus *opb = OP_BUS(bus);
> +    Error *err = NULL;
> +
> +    memory_region_init_io(&opb->mr, OBJECT(opb), &opb_unimplemented_ops, opb,
> +                          NULL, UINT32_MAX);
> +    address_space_init(&opb->as, &opb->mr, "opb");
> +
> +    object_property_set_bool(OBJECT(&opb->fsi), "realized", true, &err);
> +    if (err) {
> +        error_propagate(errp, err);
> +        return;
> +    }

Redundant local error object

> +    memory_region_add_subregion(&opb->mr, 0x80000000, &opb->fsi.iomem);
> +
> +    /* OPB2FSI region */
> +    /*
> +     * Avoid endianness issues by mapping each slave's memory region 
> directly.
> +     * Manually bridging multiple address-spaces causes endian swapping
> +     * headaches as memory_region_dispatch_read() and
> +     * memory_region_dispatch_write() correct the endianness based on the
> +     * target machine endianness and not relative to the device endianness on
> +     * either side of the bridge.
> +     */
> +    /*
> +     * XXX: This is a bit hairy and will need to be fixed when I sort out the
> +     * bus/slave relationship and any changes to the CFAM modelling (multiple
> +     * slaves, LBUS)
> +     */
> +    memory_region_add_subregion(&opb->mr, 0xa0000000, &opb->fsi.opb2fsi);
> +}
> +

> diff --git a/hw/fsi/trace-events b/hw/fsi/trace-events
> index d7afef0460..ec9bab2fe8 100644
> --- a/hw/fsi/trace-events
> +++ b/hw/fsi/trace-events
> @@ -9,3 +9,5 @@ fsi_slave_read(uint64_t addr, uint32_t size) "@0x%" PRIx64 " 
> size=%d"
>  fsi_slave_write(uint64_t addr, uint32_t size, uint64_t data) "@0x%" PRIx64 " 
> size=%d value=0x%"PRIx64
>  fsi_master_read(uint64_t addr, uint32_t size) "@0x%" PRIx64 " size=%d"
>  fsi_master_write(uint64_t addr, uint32_t size, uint64_t data) "@0x%" PRIx64 
> " size=%d value=0x%"PRIx64
> +opb_unimplemented_read(uint64_t addr, uint32_t size) "@0x%" PRIx64 " size=%d"
> +opb_unimplemented_write(uint64_t addr, uint32_t size, uint64_t data) "@0x%" 
> PRIx64 " size=%d value=0x%"PRIx64

Please consistently use an 'fsi_' prefix for all trace points, as it
makes it possible to enable all tracing for this subsystem using a
wildcard match


With regards,
Daniel
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