Re: [TF-A] [RFC] BL2 MTD frameworks - TF-A

11 Dec 2019

      Hi,
Thanks George and Lionel for your answers.
Following up and closing on this, the approach used in mentioned patch (https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/2283) looks ok provided it should now build on all platforms.
The original concern was about api breakage in the generic code, and that there might exist inconsistencies among platforms (ones depending on a 32b offset, others on 64 bits).
Changing the generic seek api offset parameter from ssize_t to signed long long everywhere as a default makes it better compliant to using larger density storage chips in the long term. This is fine as long as it also still support older lower density chips.
Regards,
Olivier.
________________________________________
From: TF-A tf-a-bounces@lists.trustedfirmware.org on behalf of Lionel DEBIEVE via TF-A tf-a@lists.trustedfirmware.org
Sent: 08 November 2019 18:34
To: tf-a@lists.trustedfirmware.org
Subject: Re: [TF-A] [RFC] BL2 MTD frameworks
Hi,
Just to clarify a little bit more.
There is no link here about a 32/64 bit architecture. The content of
this change is to take care about new memory introduce (mtd devices)
that are not based on size * LBA (where LBA=512) but size * LBA where
(LBA=1) and in such case, the size could exceed the 4GB. It is not
platform dependent and not architecture dependent, it's link to the
connected MTD device only. I'm not sure that a new type is useful except
if you want a type is modified regarding a platform flag such as
USE_LARGE_MTD_DEVICE.
Hope it's more clear.
BR,
Lionel
On 11/5/19 3:20 PM, Gyorgy Szing via TF-A wrote:
...
Hi,
I did not investigated all the details so what stays below may contain mistakes, but still I would like to add some comments.
"using a type for the offset"
The type we use for this purpose seems to be a configuration parameter for the IO layer as it depends on the upper layer being used with the IO library. For example libc uses "long int" to specify the file offset (fseek, ftell), using a different type while running below libc does not seem to be a good idea.
The best option seems to be to define a type like (as Olivier mentioned) lib/zlib does. How we set this configuration parameter during the build is a question. The offset type could be dictated by the platform, the architecture (aarch32 or aarch64) or by the user. Which one is worth to implement needs investigation.
If it is a good idea to use the same name "off_t" as zlib uses (or even the same type) is be questionable. It may give us more flexibility if we use a dedicated name, and the configuration maps the IO type to the one used by the upper layer.
"32 bit backward compatibility"
Another angle worth to consider is the 32/64 bit compatibility. I.e.: newlib can use 64 bit offsets even on 32 bit architectures, and they use some wrappers to maintain binary compatibility with old builds. When built in a compatible manner, functions using the standardized names use 32 bit wide offsets and call the real 64 bit implementation as a wrapper.
To solve compatibility issues we could use a similar pattern. Instead of changing the existing function, we could add a new one (i.e. seek64). Then new 64 bit aware code could use the new function if available, and legacy code could call the old one. Longer term it is an option to deprecate the 32 bit version.
"use stdint.h types"
And a finally: when selecting the type used for off_t (or whatever we are going to call it) please consider using stdint.h types (i.e. int_fast64_t).
/George
-----Original Message-----
From: TF-A tf-a-bounces@lists.trustedfirmware.org On Behalf Of Olivier Deprez via TF-A
Sent: 25 October 2019 14:42
To: tf-a@lists.trustedfirmware.org; Lionel DEBIEVE lionel.debieve@st.com
Subject: Re: [TF-A] [RFC] BL2 MTD frameworks
Hi Lionel,
On https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/2283
I'm extending the discussion to the TF-A ML, to get people's opinion.
The idea is to extend the io_seek offset parameter from ssize_t to unsigned long long.
There are indeed good reasons for that as flash storage density grows over the years.
Now on the change, the struct io_dev_funcs seek  function pointer is generic for the whole codebase / drivers.
So currently the change breaks the builds for at least rcar, stratix10 (did not check others from that point).
An alternative is defining offset as an off_t type which is ssize_t by default, and only unsigned long long based on the platform (using _FILE_OFFSET_BITS=64). This pattern actually already exists in lib/zlib
Other option is to change the generic prototype for all platform drivers (then we ensure all platforms build and supply platform patches).
What do ML people think?
Regards,
Olivier.

From: TF-A tf-a-bounces@lists.trustedfirmware.org on behalf of Lionel DEBIEVE via TF-A tf-a@lists.trustedfirmware.org
Sent: 18 October 2019 17:26
To: tf-a@lists.trustedfirmware.org tf-a@lists.trustedfirmware.org
Subject: [TF-A] [RFC] BL2 MTD frameworks
Hello Maintainers,
I've sent a patch series around MTD framework management into BL2 stage (cf https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/2283).
This patch series will add following frameworks:

a raw NAND framework implementation to support SLC NAND devices. Current implementation is limited to read operations without ECC corrections. Overrides are available to use hardware ECC from controller or low-level drivers. It also supports ONFI detection management but this can also be disabled or overridden by platform specific data.
a SPI-MEM framework (inspired from kernel/u-boot implementation) that encapsulates all SPI operations to SPI low level drivers.
a SPI-NAND framework based on SPI-MEM to support SPI NAND devices. This framework is also limited to the read operation. It uses single command, address and data bus width as legacy but can be overridden by platform.
a SPI-NOR framework based on SPI-MEM to manage SPI NOR devices. It is also limited to read operations using single command, address and data bus width as legacy (override still possible by platform). The framework embeds some specific implementations for manufacturers specific behavior in case of quad mode configuration activation.

This patch series also includes:

a new io_mtd interface to manage a generic access to all these frameworks.
a NAND core driver that accesses independently to raw NAND or SPI-NAND framework. This core driver requires a scratch buffer defined by platform to manage unaligned pages (could be defined to 0 in case of aligned page) and limits access to a single NAND instance management.
a complete integration is available based on STM32MP1 platform.

Tests have been performed with the following devices:
SLC NAND:

Micron MT29F8G08ABACAH4 (ONFI)
Micron MT29F8G16ABACAH4 (ONFI)
Toshiba TH58NVG3S0HTAI0 (Non ONFI)
Toshiba TC58BVG1S3HTAI0 (On die ECC)

SPI NOR:

Macronix MX25L51245G
Cypress/Spansion S25FL512
Micron  n25q512ax3

SPI-NAND:

Micron MT29F2G01ABAGD

Waiting for your comments.
Best regards, Lionel
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