Re: [RFC PATCH 5/8] cxl: create emulated cxl_hdm for devices that do not have HDM decoders

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

On Wed, 30 Nov 2022 16:12:43 -0700
Dave Jiang <dave.jiang@intel.com> wrote:

> CXL rev3 spec 8.1.3
> RCDs may not have HDM register blocks. Create a fake HDM with information
> from the CXL PCIe DVSEC registers. The decoder count will be set to the
> HDM count retrieved from the DVSEC cap register.
> 
> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
One comment inline that probably doesn't matter about setting
the target_count = 1.
If you need it to be 0 (which isn't normally a valid option) then
perhaps a comment on why.

> ---
>  drivers/cxl/core/hdm.c |   27 ++++++++++++++++++++++++++-
>  drivers/cxl/core/pci.c |    9 ++++++---
>  drivers/cxl/cxl.h      |    3 ++-
>  drivers/cxl/cxlmem.h   |    1 +
>  drivers/cxl/port.c     |    2 +-
>  5 files changed, 36 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index 9773a5efaefd..3a9e9b854587 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -96,11 +96,31 @@ static void __iomem *map_hdm_decoder_regs(struct cxl_port *port,
>  	return crb + map.hdm_decoder.offset;
>  }
>  
> +static struct cxl_hdm *devm_cxl_setup_emulated_hdm(struct cxl_port *port,
> +						   struct cxl_endpoint_dvsec_info *info)
> +{
> +	struct device *dev = &port->dev;
> +	struct cxl_hdm *cxlhdm;
> +
> +	if (!info->mem_enabled)
> +		return ERR_PTR(-ENODEV);
> +
> +	cxlhdm = devm_kzalloc(dev, sizeof(*cxlhdm), GFP_KERNEL);
> +	if (!cxlhdm)
> +		return ERR_PTR(-ENOMEM);
> +
> +	cxlhdm->port = port;
> +	cxlhdm->decoder_count = info->ranges;

Whilst I assume target_count isn't used, perhaps better to set it here
for consistency as 0 isn't a valid value for the HDM decoder related field.


> +	dev_set_drvdata(&port->dev, cxlhdm);

blank line here preferred.

> +	return cxlhdm;
> +}
> +