On Fri, Apr 14, 2023 at 11:54:11AM -0700, Dan Williams wrote:
> Do not assume that a single-target port falls back to a passthrough
> decoder configuration. Scan for decoders and only fallback after probing
> that the HDM decoder capability is not present.
>
> One user visible affect of this bug is the inability to enumerate
> present CXL regions as the decoder settings for the present decoders are
> skipped.
>
> Fixes: d17d0540a0db ("cxl/core/hdm: Add CXL standard decoder enumeration to the core")
> Reported-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> Link: http://lore.kernel.org/r/20230227153128.8164-1-Jonathan.Cameron@xxxxxxxxxx
> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Reviewed-by: Alison Schofield <alison.schofield@xxxxxxxxx>
> ---
> drivers/cxl/core/hdm.c | 5 +++--
> drivers/cxl/port.c | 18 +++++++++++++-----
> 2 files changed, 16 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 6fdf7981ddc7..abe3877cfa63 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -92,8 +92,9 @@ static int map_hdm_decoder_regs(struct cxl_port *port, void __iomem *crb,
>
> cxl_probe_component_regs(&port->dev, crb, &map.component_map);
> if (!map.component_map.hdm_decoder.valid) {
> - dev_err(&port->dev, "HDM decoder registers invalid\n");
> - return -ENXIO;
> + dev_dbg(&port->dev, "HDM decoder registers not implemented\n");
> + /* unique error code to indicate no HDM decoder capability */
> + return -ENODEV;
> }
>
> return cxl_map_component_regs(&port->dev, regs, &map,
> diff --git a/drivers/cxl/port.c b/drivers/cxl/port.c
> index 22a7ab2bae7c..eb57324c4ad4 100644
> --- a/drivers/cxl/port.c
> +++ b/drivers/cxl/port.c
> @@ -66,14 +66,22 @@ static int cxl_switch_port_probe(struct cxl_port *port)
> if (rc < 0)
> return rc;
>
> - if (rc == 1)
> - return devm_cxl_add_passthrough_decoder(port);
> -
> cxlhdm = devm_cxl_setup_hdm(port, NULL);
> - if (IS_ERR(cxlhdm))
> + if (!IS_ERR(cxlhdm))
> + return devm_cxl_enumerate_decoders(cxlhdm, NULL);
> +
> + if (PTR_ERR(cxlhdm) != -ENODEV) {
> + dev_err(&port->dev, "Failed to map HDM decoder capability\n");
> return PTR_ERR(cxlhdm);
> + }
> +
> + if (rc == 1) {
> + dev_dbg(&port->dev, "Fallback to passthrough decoder\n");
> + return devm_cxl_add_passthrough_decoder(port);
> + }
>
> - return devm_cxl_enumerate_decoders(cxlhdm, NULL);
> + dev_err(&port->dev, "HDM decoder capability not found\n");
> + return -ENXIO;
> }
>
> static int cxl_endpoint_port_probe(struct cxl_port *port)
>
