linux-kernel - Re: [PATCH 01/26] cxl/mbox: Flag support for Dynamic Capacity Devices (DCD)

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Date: Wed, 10 Apr 2024 11:15:32 -0700
From: Alison Schofield <alison.schofield@...el.com>
To: ira.weiny@...el.com
Cc: Dave Jiang <dave.jiang@...el.com>, Fan Ni <fan.ni@...sung.com>,
	Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Navneet Singh <navneet.singh@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Vishal Verma <vishal.l.verma@...el.com>,
	linux-btrfs@...r.kernel.org, linux-cxl@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/26] cxl/mbox: Flag support for Dynamic Capacity
 Devices (DCD)

On Sun, Mar 24, 2024 at 04:18:04PM -0700, Ira Weiny wrote:
> From: Navneet Singh <navneet.singh@...el.com>
> 
> Per the CXL 3.1 specification software must check the Command Effects
> Log (CEL) to know if a device supports dynamic capacity (DC).  If the
> device does support DC the specifics of the DC Regions (0-7) are read
> through the mailbox.

Do I need to know this 'If the device...' piece to understand this
patch?  I like that below you say 'Subsequent patches will...'
That seems enough to set the scene.

> 
> Flag DC Device (DCD) commands in a device if they are supported.
Why be vague w 'Flag'. How about 'Add a bitmap of DCD enabled
commands to the driver device state structure.'

> Subsequent patches will key off these bits to configure DCD.
> 
> Signed-off-by: Navneet Singh <navneet.singh@...el.com>
> Co-developed-by: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> ---
> Changes for v1
> [iweiny: update to latest master]
> [iweiny: update commit message]
> [iweiny: Based on the fix:
> 	https://lore.kernel.org/all/20230903-cxl-cel-fix-v1-1-e260c9467be3@intel.com/
> [jonathan: remove unneeded format change]
> [jonathan: don't split security code in mbox.c]
> ---
>  drivers/cxl/core/mbox.c | 33 +++++++++++++++++++++++++++++++++
>  drivers/cxl/cxlmem.h    | 15 +++++++++++++++
>  2 files changed, 48 insertions(+)
> 

snip


>  /* Device enabled poison commands */
>  enum poison_cmd_enabled_bits {
>  	CXL_POISON_ENABLED_LIST,
> @@ -454,6 +463,7 @@ struct cxl_dev_state {
>   *                (CXL 2.0 8.2.9.5.1.1 Identify Memory Device)
>   * @mbox_mutex: Mutex to synchronize mailbox access.
>   * @firmware_version: Firmware version for the memory device.
> + * @dcd_cmds: List of DCD commands implemented by memory device
>   * @enabled_cmds: Hardware commands found enabled in CEL.
>   * @exclusive_cmds: Commands that are kernel-internal only

It's not a 'List' it's a bitmap. How about mimicing 'enabled_cmds' 
description:

* @dcd_cmds: DCD commands found enabled in CEL

>   * @total_bytes: sum of all possible capacities
> @@ -481,6 +491,7 @@ struct cxl_memdev_state {
>  	size_t lsa_size;
>  	struct mutex mbox_mutex; /* Protects device mailbox and firmware */
>  	char firmware_version[0x10];
> +	DECLARE_BITMAP(dcd_cmds, CXL_DCD_ENABLED_MAX);
>  	DECLARE_BITMAP(enabled_cmds, CXL_MEM_COMMAND_ID_MAX);
>  	DECLARE_BITMAP(exclusive_cmds, CXL_MEM_COMMAND_ID_MAX);
>  	u64 total_bytes;
> @@ -551,6 +562,10 @@ enum cxl_opcode {
>  	CXL_MBOX_OP_UNLOCK		= 0x4503,
>  	CXL_MBOX_OP_FREEZE_SECURITY	= 0x4504,
>  	CXL_MBOX_OP_PASSPHRASE_SECURE_ERASE	= 0x4505,
> +	CXL_MBOX_OP_GET_DC_CONFIG	= 0x4800,
> +	CXL_MBOX_OP_GET_DC_EXTENT_LIST	= 0x4801,
> +	CXL_MBOX_OP_ADD_DC_RESPONSE	= 0x4802,
> +	CXL_MBOX_OP_RELEASE_DC		= 0x4803,
>  	CXL_MBOX_OP_MAX			= 0x10000
>  };
>  
> 
> -- 
> 2.44.0
>