Re: [RESEND PATCH v13 2/8] cxl/mem: Read dynamic capacity configuration from the device

[Davidlohr Bueso <dave@stgolabs.net>]

On 2026-09-08 03:15, Anisa Su wrote:
> From: Ira Weiny <iweiny@kernel.org>
> 
> Devices which support Dynamic Capacity (DC) are configured
> via mailbox commands. CXL r4.0 section 9.13.3 requires the host to 
> issue
> the Get DC Configuration command in order to properly configure DCDs.
> 
> Implement the DC mailbox commands as specified in CXL 4.0 section
> 8.2.10.9.9 (opcodes 48XXh) to read and store the DCD configuration
> information. Disable DCD if an invalid configuration is found.
> 
> Linux has no support for more than one dynamic capacity partition. Read
> all the partitions the device reports but validate only the first, and
> configure it as 'dynamic ram 1'.
> 
> The specification requires that volatile capacity starts at DPA 0 and 
> pmem
> starts at the DPA immediately following it, but DC partitions only need
> to be 256MB aligned according to CXL r4.0 section 8.2.10.9.9.1 Table 
> 8-347.
> So a device could leave a gap between ram/pmem (static) capacity and 
> its first
> DC partition, or between one DC partition and the next.
> 
> However, Linux follows the precedent set by PMEM/RAM partitions and 
> requires the
> first DC partition to begin at the DPA immediately following static
> capacity.
> 
> Based on an original patch by Navneet Singh.
> 
> Signed-off-by: Ira Weiny <iweiny@kernel.org>
> Signed-off-by: Anisa Su <anisa.su@samsung.com>
> Tested-by: Wonjae Lee <wj28.lee@samsung.com>
> Tested-by: Junhee Park <jh9934.park@samsung.com>
> Tested-by: Heesoo Kim <habil.kim@samsung.com>

Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>