Re: [PATCH v5 4/5] mmc: sdhci-tegra: Implement alternative_gpt_sector()

[Ulf Hansson <ulf.hansson@linaro.org>]

On Wed, 18 Aug 2021 at 15:35, Thierry Reding <thierry.reding@gmail.com> wrote:
>
> On Wed, Aug 18, 2021 at 11:55:05AM +0200, Ulf Hansson wrote:
> > On Wed, 18 Aug 2021 at 02:57, Dmitry Osipenko <digetx@gmail.com> wrote:
> > >
> > > Tegra20/30/114/124 Android devices place GPT at a non-standard location.
> > > Implement alternative_gpt_sector() callback of the MMC host ops which
> > > specifies that GPT location for the partition scanner.
> > >
> > > Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
> > > ---
> > >  drivers/mmc/host/sdhci-tegra.c | 42 ++++++++++++++++++++++++++++++++++
> > >  1 file changed, 42 insertions(+)
> > >
> > > diff --git a/drivers/mmc/host/sdhci-tegra.c b/drivers/mmc/host/sdhci-tegra.c
> > > index 387ce9cdbd7c..24a713689d5b 100644
> > > --- a/drivers/mmc/host/sdhci-tegra.c
> > > +++ b/drivers/mmc/host/sdhci-tegra.c
> > > @@ -116,6 +116,8 @@
> > >   */
> > >  #define NVQUIRK_HAS_TMCLK                              BIT(10)
> > >
> > > +#define NVQUIRK_HAS_ANDROID_GPT_SECTOR                 BIT(11)
> > > +
> > >  /* SDMMC CQE Base Address for Tegra Host Ver 4.1 and Higher */
> > >  #define SDHCI_TEGRA_CQE_BASE_ADDR                      0xF000
> > >
> > > @@ -1361,6 +1363,7 @@ static const struct sdhci_tegra_soc_data soc_data_tegra20 = {
> > >         .pdata = &sdhci_tegra20_pdata,
> > >         .dma_mask = DMA_BIT_MASK(32),
> > >         .nvquirks = NVQUIRK_FORCE_SDHCI_SPEC_200 |
> > > +                   NVQUIRK_HAS_ANDROID_GPT_SECTOR |
> > >                     NVQUIRK_ENABLE_BLOCK_GAP_DET,
> > >  };
> > >
> > > @@ -1390,6 +1393,7 @@ static const struct sdhci_tegra_soc_data soc_data_tegra30 = {
> > >         .nvquirks = NVQUIRK_ENABLE_SDHCI_SPEC_300 |
> > >                     NVQUIRK_ENABLE_SDR50 |
> > >                     NVQUIRK_ENABLE_SDR104 |
> > > +                   NVQUIRK_HAS_ANDROID_GPT_SECTOR |
> > >                     NVQUIRK_HAS_PADCALIB,
> > >  };
> > >
> > > @@ -1422,6 +1426,7 @@ static const struct sdhci_pltfm_data sdhci_tegra114_pdata = {
> > >  static const struct sdhci_tegra_soc_data soc_data_tegra114 = {
> > >         .pdata = &sdhci_tegra114_pdata,
> > >         .dma_mask = DMA_BIT_MASK(32),
> > > +       .nvquirks = NVQUIRK_HAS_ANDROID_GPT_SECTOR,
> > >  };
> > >
> > >  static const struct sdhci_pltfm_data sdhci_tegra124_pdata = {
> > > @@ -1438,6 +1443,7 @@ static const struct sdhci_pltfm_data sdhci_tegra124_pdata = {
> > >  static const struct sdhci_tegra_soc_data soc_data_tegra124 = {
> > >         .pdata = &sdhci_tegra124_pdata,
> > >         .dma_mask = DMA_BIT_MASK(34),
> > > +       .nvquirks = NVQUIRK_HAS_ANDROID_GPT_SECTOR,
> > >  };
> > >
> > >  static const struct sdhci_ops tegra210_sdhci_ops = {
> > > @@ -1590,6 +1596,38 @@ static int sdhci_tegra_add_host(struct sdhci_host *host)
> > >         return ret;
> > >  }
> > >
> > > +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.

Good point!

Perhaps naming the cap MMC_CAP_TEGRA_GPT would make this more clear.

>
> 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 certainly don't want to legitimize this. But no matter what, that is
exactly what we are doing, anyways.

In summary, I still prefer code to be put in their proper layers, and
there aren't any host specific things going on here, except for
parsing a compatible string.

Kind regards
Uffe