Re: [Qemu-ppc] [PATCHv2 04/11] libqos: Better handling of PCI legacy IO

[Laurent Vivier]

On 19/10/2016 14:25, David Gibson wrote:
> The usual model for PCI IO with libqos is to use qpci_iomap() to map a
> specific BAR for a PCI device, then perform IOs within that BAR using
> qpci_io_{read,write}*().
> 
> However, certain devices also have legacy PCI IO.  In this case, instead of
> (or as well as) being accessed via PCI BARs, the device can be accessed
> via certain well-known, fixed addresses in PCI IO space.
> 
> Two existing tests use legacy PCI IO, and take different flawed approaches
> to it:
>     * tco-test manually constructs a tco_io_base value instead of calling
>       qpci_iomap(), which assumes internal knowledge of the structure of
>       the value it shouldn't have
>     * ide-test uses direct in*() and out*() calls instead of using
>       qpci_io_*() accessors, meaning it's not portable to non-x86 machine
>       types.
> 
> tco_test uses the libqos PCI code to access the device.  This makes perfect
> sense for the PCI config space accesses.  However for IO, rather than the
> usual PCI approach of mapping a PCI BAR, then accessing that, it instead
> uses the legacy approach of fixed, known addresses in PCI IO space.
> 
> That doesn't work very well with the qpci_io_{read,write} functions because
> we never use qpci_iomap() and so have to make assumptions about the
> internal encoding of the address tokens iomap() returns.
> 
> This patch avoids that, by directly using the bus's pio_{read,write}
> callbacks, which are defined to take addresses within the PCI IO space.
> 
> Signed-off-by: David Gibson <address@hidden>

This patch makes sense but it is not obvious (at least for me) why you
are doing this if I don't read patch 11/11 before...

Reviewed-by: Laurent Vivier <address@hidden>

> ---
>  tests/libqos/pci.c | 5 +++++
>  tests/libqos/pci.h | 1 +
>  2 files changed, 6 insertions(+)
> 
> diff --git a/tests/libqos/pci.c b/tests/libqos/pci.c
> index bf1c532..98a2e56 100644
> --- a/tests/libqos/pci.c
> +++ b/tests/libqos/pci.c
> @@ -350,6 +350,11 @@ void qpci_iounmap(QPCIDevice *dev, void *data)
>      /* FIXME */
>  }
>  
> +void *qpci_legacy_iomap(QPCIDevice *dev, uint16_t addr)
> +{
> +    return (void *)(uintptr_t)addr;
> +}
> +
>  void qpci_plug_device_test(const char *driver, const char *id,
>                             uint8_t slot, const char *opts)
>  {
> diff --git a/tests/libqos/pci.h b/tests/libqos/pci.h
> index f6f916d..b6f855e 100644
> --- a/tests/libqos/pci.h
> +++ b/tests/libqos/pci.h
> @@ -94,6 +94,7 @@ void qpci_io_writel(QPCIDevice *dev, void *data, uint32_t 
> value);
>  
>  void *qpci_iomap(QPCIDevice *dev, int barno, uint64_t *sizeptr);
>  void qpci_iounmap(QPCIDevice *dev, void *data);
> +void *qpci_legacy_iomap(QPCIDevice *dev, uint16_t addr);
>  
>  void qpci_plug_device_test(const char *driver, const char *id,
>                             uint8_t slot, const char *opts);
>