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From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Wed, 4 Mar 2020 17:36:46 +0100
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Subject: Re: [PATCH v1 3/3] partitions: Introduce NVIDIA Tegra Partition Table
To:     Stephen Warren <swarren@wwwdotorg.org>,
        Dmitry Osipenko <digetx@gmail.com>
Cc:     Jens Axboe <axboe@kernel.dk>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= <mirq-linux@rere.qmqm.pl>,
        David Heidelberg <david@ixit.cz>,
        Peter Geis <pgwipeout@gmail.com>,
        Nicolas Chauvet <kwizart@gmail.com>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Billy Laws <blaws05@gmail.com>,
        linux-tegra <linux-tegra@vger.kernel.org>,
        linux-block <linux-block@vger.kernel.org>,
        Andrey Danin <danindrey@mail.ru>,
        Gilles Grandou <gilles@grandou.net>,
        Ryan Grachek <ryan@edited.us>,
        "linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Tue, 25 Feb 2020 at 01:20, Stephen Warren <swarren@wwwdotorg.org> wrote:
>
> On 2/24/20 4:18 PM, Dmitry Osipenko wrote:
> > All NVIDIA Tegra devices use a special partition table format for the
> > internal storage partitioning. Most of Tegra devices have GPT partition
> > in addition to TegraPT, but some older Android consumer-grade devices do
> > not or GPT is placed in a wrong sector, and thus, the TegraPT is needed
> > in order to support these devices properly in the upstream kernel. This
> > patch adds support for NVIDIA Tegra Partition Table format that is used
> > at least by all NVIDIA Tegra20 and Tegra30 devices.
>
> > diff --git a/arch/arm/mach-tegra/tegra.c b/arch/arm/mach-tegra/tegra.c
>
> > +static void __init tegra_boot_config_table_init(void)
> > +{
> > +     void __iomem *bct_base;
> > +     u16 pt_addr, pt_size;
> > +
> > +     bct_base = IO_ADDRESS(TEGRA_IRAM_BASE) + TEGRA_IRAM_BCT_OFFSET;
>
> This shouldn't be hard-coded. IIRC, the boot ROM writes a BIT (Boot
> Information Table) to a fixed location in IRAM, and there's some value
> in the BIT that points to where the BCT is in IRAM. In practice, it
> might work out that the BCT is always at the same place in IRAM, but
> this certainly isn't guaranteed. I think there's code in U-Boot which
> extracts the BCT location from the BIT? Yes, see
> arch/arm/mach-tegra/ap.c:get_odmdata().

So, have you considered using the command line partition option,
rather than adding yet another partition scheme to the kernel?

In principle, you would let the boot loader scan for the partitions,
likely from machine specific code in U-boot. Then you append these to
the kernel command line and let block/partitions/cmdline.c scan for
it.

Kind regards
Uffe