Re: [PATCH v8 11/11] tools/testing/cxl: Add decoder save/restore support

[Jonathan Cameron <Jonathan.Cameron@huawei.com>]

On Thu, 14 Aug 2025 15:21:51 -0700
Dave Jiang <dave.jiang@intel.com> wrote:

> Record decoder values at init and mock_decoder_commit() time, and
> restore them at the next invocation of mock_init_hdm_decoder(). Add 2
> attributes to the cxl_test "cxl_acpi" device to optionally flush the
> cache of topology decoder values, or disable updating the decoder at
> mock_decoder_reset() time.
> 
> This enables replaying a saved decoder configuration when re-triggering
> a topology scan by re-binding the cxl_acpi driver to "cxl_acpi.0" (the
> cxl_test emulation of an ACPI0017 instance).
> 
>     # modprobe cxl_test
>     # cxl list -RB -b cxl_test -u
>     {
>       "bus":"root3",
>       "provider":"cxl_test",
>       "regions:root3":[
>         {
>           "region":"region5",
>           "resource":"0xf010000000",
>           "size":"512.00 MiB (536.87 MB)",
>           "type":"ram",
>           "interleave_ways":2,
>           "interleave_granularity":4096,
>           "decode_state":"commit"
>         }
>       ]
>     }
>     # echo 1 > /sys/bus/platform/devices/cxl_acpi.0/decoder_registry_reset_disable
>     # echo cxl_acpi.0 > /sys/bus/platform/drivers/cxl_acpi/unbind
>     # cxl list -RB -b cxl_test -u
>     # echo cxl_acpi.0 > /sys/bus/platform/drivers/cxl_acpi/bind
>     # cxl list -RB -b cxl_test -u
>     {
>       "bus":"root3",
>       "provider":"cxl_test",
>       "regions:root3":[
>         {
>           "region":"region5",
>           "resource":"0xf010000000",
>           "size":"512.00 MiB (536.87 MB)",
>           "type":"ram",
>           "interleave_ways":2,
>           "interleave_granularity":4096,
>           "decode_state":"commit"
>         }
>       ]
>     }
> 
> [dj: Added support for delayed dport initialization ]
> 
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Authorship wrong, or a Co-dev missing?  Was expecting to see  a From: Dan...


> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> ---
> - Will have a cxl-replay test script in CXL CLI package
> - This allowed me to test assembly and replay for manually created CXL regions
> ---
>  tools/testing/cxl/test/cxl.c | 300 ++++++++++++++++++++++++++++++++++-
>  1 file changed, 298 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/cxl/test/cxl.c b/tools/testing/cxl/test/cxl.c
> index 2d50193d10fe..e0da2a48d2a8 100644
> --- a/tools/testing/cxl/test/cxl.c
> +++ b/tools/testing/cxl/test/cxl.c
> @@ -47,6 +47,9 @@ struct platform_device *cxl_mem_single[NR_MEM_SINGLE];
>  static struct platform_device *cxl_rch[NR_CXL_RCH];
>  static struct platform_device *cxl_rcd[NR_CXL_RCH];
>  
> +static DEFINE_XARRAY(decoder_registry);
> +static bool decoder_registry_reset_disable;
> +
>  static inline bool is_multi_bridge(struct device *dev)
>  {
>  	int i;
> @@ -671,6 +674,164 @@ static int map_targets(struct device *dev, void *data)
>  	return 0;
>  }
>  
> +static unsigned long cxld_registry_index(struct cxl_decoder *cxld)
> +{
> +	struct cxl_port *port = to_cxl_port(cxld->dev.parent);
> +
> +	/*
> +	 * Upper nibble of a kernel pointer is 0xff, chop that to make

Very unlikely a nibble is 0xff, more likely 0xf unless you x86 folk have
8 bit nibbles :)

> +	 * space for a cxl_decoder id which should be less than 128
> +	 * given decoder count is a 4-bit field.

If it's a 4 bit field, how can it be greater than 15?
Maybe I need more coffee.

> +	 *
> +	 * While @port is reallocated each enumeration, @port->uport_dev
> +	 * is stable.
> +	 */
> +	dev_WARN_ONCE(&port->dev, cxld->id >= 128,
> +		      "decoder id:%d out of range\n", cxld->id);
> +	return (((unsigned long) port->uport_dev) << 4) | cxld->id;
> +}