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From: Thierry Reding <thierry.reding@gmail.com>
To: Dmitry Osipenko <digetx@gmail.com>
Cc: "Ulf Hansson" <ulf.hansson@linaro.org>,
	"Jens Axboe" <axboe@kernel.dk>,
	"Jonathan Hunter" <jonathanh@nvidia.com>,
	"Michał Mirosław" <mirq-linux@rere.qmqm.pl>,
	"David Heidelberg" <david@ixit.cz>,
	"Peter Geis" <pgwipeout@gmail.com>,
	"Adrian Hunter" <adrian.hunter@intel.com>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Davidlohr Bueso" <dave@stgolabs.net>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Ion Agorria" <AG0RRIA@yahoo.com>,
	"Svyatoslav Ryhel" <clamor95@gmail.com>,
	linux-tegra <linux-tegra@vger.kernel.org>,
	linux-block <linux-block@vger.kernel.org>,
	linux-efi <linux-efi@vger.kernel.org>
Subject: Re: [PATCH v5 4/5] mmc: sdhci-tegra: Implement alternative_gpt_sector()
Date: Thu, 19 Aug 2021 10:58:46 +0200	[thread overview]
Message-ID: <YR4dRuhjOBDkNAa7@orome.fritz.box> (raw)
In-Reply-To: <90dcb1e9-30df-e721-5ddc-156ae295636e@gmail.com>

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On Wed, Aug 18, 2021 at 07:15:43PM +0300, Dmitry Osipenko wrote:
> 18.08.2021 16:35, Thierry Reding пишет:
> >>> +static int sdhci_tegra_alternative_gpt_sector(struct mmc_card *card,
> >>> +                                             sector_t *gpt_sector)
> >>> +{
> >>> +       unsigned int boot_sectors_num;
> >>> +
> >>> +       /* filter out unrelated cards */
> >>> +       if (card->ext_csd.rev < 3 ||
> >>> +           !mmc_card_mmc(card) ||
> >>> +           !mmc_card_is_blockaddr(card) ||
> >>> +            mmc_card_is_removable(card->host))
> >>> +               return -ENOENT;
> >>> +
> >>> +       /*
> >>> +        * eMMC storage has two special boot partitions in addition to the
> >>> +        * main one.  NVIDIA's bootloader linearizes eMMC boot0->boot1->main
> >>> +        * accesses, this means that the partition table addresses are shifted
> >>> +        * by the size of boot partitions.  In accordance with the eMMC
> >>> +        * specification, the boot partition size is calculated as follows:
> >>> +        *
> >>> +        *      boot partition size = 128K byte x BOOT_SIZE_MULT
> >>> +        *
> >>> +        * Calculate number of sectors occupied by the both boot partitions.
> >>> +        */
> >>> +       boot_sectors_num = card->ext_csd.raw_boot_mult * SZ_128K /
> >>> +                          SZ_512 * MMC_NUM_BOOT_PARTITION;
> >>> +
> >>> +       /* Defined by NVIDIA and used by Android devices. */
> >>> +       *gpt_sector = card->ext_csd.sectors - boot_sectors_num - 1;
> >>> +
> >>> +       return 0;
> >>> +}
> >> I suggest you move this code into the mmc core/block layer instead (it
> >> better belongs there).
> >>
> >> Additionally, let's add a new host cap, MMC_CAP_ALTERNATIVE_GPT, to
> >> let the core know when it should use the code above.
> > Couldn't a generic "alternative GPT" mean pretty much anything? As far
> > as I know this is very specific to a series of Tegra chips and firmware
> > running on them. On some of these devices you can even replace the OEM
> > firmware by something custom that's less quirky.
> > 
> > I'm not aware of anyone else employing this kind of quirk, so I don't
> > want anyone to get any ideas that this is a good thing. Putting it into
> > the core runs the risk of legitimizing this.
> 
> I also think it's better to keep it internal to Tegra. Ulf, could you
> please clarify why do you want to have it moved into the core? Are you
> aware of any other platforms that want exactly the same quirk? Thierry
> should be correct that it's relevant only to Tegra SoCs.
> 
> Regarding the 'legitimizing', it's not a bad thing to me at all. If we
> want to run more devices with a mainline kernel, then such quirks are
> inevitable.

That's not what I meant. What I meant to say is that putting it into the
core might give somebody else the idea that this is actually a good
thing and therefore they might end up implementing a similar quirk. That
is definitely not something we want to encourage.

Thierry

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  reply	other threads:[~2021-08-19  8:58 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18  0:55 [PATCH v5 0/5] Support EFI partition on NVIDIA Tegra devices Dmitry Osipenko
2021-08-18  0:55 ` [PATCH v5 1/5] block: Add alternative_gpt_sector() operation Dmitry Osipenko
2021-08-18  5:20   ` Christoph Hellwig
2021-08-18  5:41     ` Dmitry Osipenko
2021-08-18  0:55 ` [PATCH v5 2/5] mmc: block: Support " Dmitry Osipenko
2021-08-18  5:28   ` Christoph Hellwig
2021-08-18  5:40     ` Dmitry Osipenko
2021-08-18  0:55 ` [PATCH v5 3/5] mmc: core: Add raw_boot_mult field to mmc_ext_csd Dmitry Osipenko
2021-08-18  0:55 ` [PATCH v5 4/5] mmc: sdhci-tegra: Implement alternative_gpt_sector() Dmitry Osipenko
2021-08-18  5:30   ` Christoph Hellwig
2021-08-18  5:42     ` Dmitry Osipenko
2021-08-18  9:55   ` Ulf Hansson
2021-08-18 13:35     ` Thierry Reding
2021-08-18 16:15       ` Dmitry Osipenko
2021-08-19  8:58         ` Thierry Reding [this message]
2021-08-19 13:20       ` Ulf Hansson
2021-08-19 17:19         ` Thierry Reding
2021-08-20  8:16           ` Ulf Hansson
2021-08-18  0:55 ` [PATCH v5 5/5] partitions/efi: Support non-standard GPT location Dmitry Osipenko
2021-08-18  5:25   ` Christoph Hellwig
2021-08-18  5:41     ` Dmitry Osipenko

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