Re: Universal Flash Storage Driver Proposal

Hi Jaeyoon

This sounds really cool!

What layering scheme did you have in mind to allow multiple storage devices
per
controller? Will it be a new kind of SIM in the CAM layer, or will it be
SCSI with
a different transport? Is this a full SCSI implementation, or will the CAM
periph
drivers need to restrict the requests they send down for this? We already
have a
number of subsets that we handle in an ad-hoc way, but maybe we need to be
a little
more organized about it.

In the past, I've helped with the MMC and NVMe integration intro CAM, so I
have
an interest....

Warner

On Thu, Jan 16, 2025 at 9:54 PM Jaeyoon Choi <j_yoon.choi@samsung.com>
wrote:

> Hello,
>
> As I mentioned in my previous email to the mailing list last year, I am
> planning
> to start developing a Universal Flash Storage Driver.
> - https://lists.freebsd.org/archives/freebsd-hackers/2024-July/003385.html
> Before I begin working on the driver, I would like to share my development
> plan
> with you.
>
> Universal Flash Storage (UFS) is a storage device for mobile devices which
> aims
> for high performance and low power consumption.
> UFS is currently used in most smartphones and tablets, and I believe there
> is a
> demand for UFS support in FreeBSD.
>
> The Universal Flash Storage Driver is named UFSHCI to avoid confusion with
> the
> UFS filesystem, and is located in the /sys/dev/ufshci folder.
>
> The driver will be developed based on the UFS 4.1 (JESD220G) and UFSHCI 4.1
> (JESD223F) specification documents, which are the latest versions
> available.
> The latest specifications can be found at the following link:
> -
> https://www.jedec.org/standards-documents/focus/flash/universal-flash-storage-ufs
>
> My plan is to first implement a PCIe-based driver and then make it
> compatible
> with various smartphone application processors.
> Since UFS uses SCSI commands, we need to use the SCSI I/O path of the CAM.
>
> Please note that there is currently a UFSHCI driver in development for
> OpenBSD,
> but due to its low spec version (UFSHCI 2.1) and lack of compatibility with
> FreeBSD, I have decided to start from scratch.
>
> The following platforms will be used for testing:
> - QEMU with Emulated UFS device
> - Samsung Galaxy Book S (Intel Lakefield + eUFS)
> - Lenovo Duet3 11ian8 (Intel N100 + eUFS)
>
> After developing the UFSHCI driver, I will continue to work on additional
> features and keep the driver up-to-date with the latest specs.
> The approximate development plan is as follows:
>
> - 2025 1H: Implementation of initialization, basic operations, and single
>            doorbell-based read/write I/O on Intel CPU-based platforms
> - 2025 2H: Implementation of MCQ-based read/write I/O, and implementation
> of
>            additional features such as writebooster
>
> I look forward to receiving your feedback and suggestions.
>
> Best regards,
> Jaeyoon
>
>