Re: [PATCH 17/23] cxl: Cache and pass DVSEC ranges

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

On Fri, 19 Nov 2021 16:02:44 -0800
Ben Widawsky <ben.widawsky@intel.com> wrote:

> CXL 1.1 specification provided a mechanism for mapping an address space
> of a CXL device. That functionality is known as a "range" and can be
> programmed through PCIe DVSEC. In addition to this, the specification
> defines an active bit which a device will expose through the same DVSEC
> to notify system software that memory is initialized and ready.
> 
> While CXL 2.0 introduces a more powerful mechanism called HDM decoders
> that are controlled by MMIO behind a PCIe BAR, the spec does allow the
> 1.1 style mapping to still be present. In such a case, when the CXL
> driver takes over, if it were to enable HDM decoding and there was an
> actively used range, things would likely blow up, in particular if it
> wasn't an identical mapping.
> 
> This patch caches the relevant information which the cxl_mem driver will
> need to make the proper decision and passes it along.
> 
> Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> ---
>  drivers/cxl/cxlmem.h |  19 +++++++
>  drivers/cxl/pci.c    | 126 +++++++++++++++++++++++++++++++++++++++++++
>  drivers/cxl/pci.h    |  13 +++++
>  3 files changed, 158 insertions(+)
> 
> diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
> index 3ef3c652599e..eac5528ccaae 100644
> --- a/drivers/cxl/cxlmem.h
> +++ b/drivers/cxl/cxlmem.h
> @@ -89,6 +89,22 @@ struct cxl_mbox_cmd {
>   */
>  #define CXL_CAPACITY_MULTIPLIER SZ_256M
>  
> +/**
> + * struct cxl_endpoint_dvsec_info - Cached DVSEC info
> + * @mem_enabled: cached value of mem_enabled in the DVSEC, PCIE_DEVICE
> + * @ranges: Number of HDM ranges this device contains.
> + * @range.base: cached value of the range base in the DVSEC, PCIE_DEVICE
> + * @range.size: cached value of the range size in the DVSEC, PCIE_DEVICE
> + */
> +struct cxl_endpoint_dvsec_info {
> +	bool mem_enabled;
> +	int ranges;
> +	struct {
> +		u64 base;
> +		u64 size;
> +	} range[2];

kernel-doc wants documentation for range as well.

> +};