Re: [PATCH v20 08/12] mmc: renesas_sdhi: Add RZ/G3L SDHI support

[Geert Uytterhoeven]

Hi Biju,

On Mon, 13 Jul 2026 at 19:52, Biju <biju.das.au@xxxxxxxxx> wrote:
> From: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
>
> The RZ/G3L SoC (r9a08g046) has an SDHI controller with several
> differences from existing platforms, requiring dedicated handling.
>
> Utilise the TMIO_MMC_HWADJ flag to identify controllers that carry
> a second hardware adjustment register (SDm_SCC_HWADJ2 at offset 0x010).
> When both TMIO_MMC_TUNING_DELAY and TMIO_MMC_HWADJ are set,
> renesas_sdhi_set_hw_adjustment_delay() additionally programs HWADJ2
> with 0x3FFF at 3.3 V and 0xFF at 1.8 V. A new RZG3L_SDHI_SCC_HWADJ4
> register (offset 0x022) is also cleared at the start of tuning when
> TMIO_MMC_INTERNAL_DIVIDER is set.
>
> Add a new version constant SDHI_VER_RZ_G3L_SDMMC (0xce10) and extend
> renesas_sdhi_sdbuf_width() to handle it alongside the existing Gen3
> variants.
>
> Introduce of_data_rzg3l with RZ/G3L-specific parameters: a wider
> clk_mask of 0x200000200, a max_divider of 2048 (reflecting the 11-bit
> divider), a dedicated rzg3l_scc_taps table, and all relevant tmio_flags,
> including TMIO_MMC_INTERNAL_DIVIDER and TMIO_MMC_HWADJ. Wire it to a
> new of_rzg3l_compatible entry using sdhi_quirks_rzg3l (which sets
> fixed_addr_mode), and register the "renesas,sdhi-r9a08g046" compatible
> string in the OF match table.
>
> Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>

Thanks for your patch!

This causes a division by zero on Armadillo (R-Mobile A1):

    Division by zero in kernel.
    CPU: 0 UID: 0 PID: 22 Comm: kworker/0:2 Not tainted
7.2.0-rc3-armadillo-06338-gd1557670ab0c #976 VOLUNTARY
    Hardware name: Generic R8A7740 (Flattened Device Tree)
    Workqueue: events_freezable mmc_rescan
    Call trace:
     unwind_backtrace from show_stack+0x10/0x14
     show_stack from dump_stack_lvl+0x44/0x74
     dump_stack_lvl from Ldiv0+0x8/0x10
     Ldiv0 from tmio_mmc_set_ios+0x11c/0x1bc
     tmio_mmc_set_ios from mmc_sdio_init_card+0xa40/0xab8
     mmc_sdio_init_card from mmc_attach_sdio+0x90/0x32c
     mmc_attach_sdio from mmc_rescan+0x1d8/0x2a4
     mmc_rescan from process_scheduled_works+0x2bc/0x45c
     process_scheduled_works from worker_thread+0x170/0x214
     worker_thread from kthread+0x114/0x124
     kthread from ret_from_fork+0x14/0x28
    Exception stack(0xe0945fb0 to 0xe0945ff8)
    5fa0:                                     00000000 00000000
00000000 00000000
    5fc0: 00000000 00000000 00000000 00000000 00000000 00000000
00000000 00000000
    5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
    Division by zero in kernel.
    CPU: 0 UID: 0 PID: 22 Comm: kworker/0:2 Not tainted
7.2.0-rc3-armadillo-06338-gd1557670ab0c #976 VOLUNTARY
    Hardware name: Generic R8A7740 (Flattened Device Tree)
    Workqueue: events_freezable mmc_rescan
    Call trace:
     unwind_backtrace from show_stack+0x10/0x14
     show_stack from dump_stack_lvl+0x44/0x74
     dump_stack_lvl from Ldiv0+0x8/0x10
     Ldiv0 from tmio_mmc_set_ios+0x11c/0x1bc
     tmio_mmc_set_ios from sdio_enable_4bit_bus+0x120/0x138
     sdio_enable_4bit_bus from mmc_sdio_init_card+0xa48/0xab8
     mmc_sdio_init_card from mmc_attach_sdio+0x90/0x32c
     mmc_attach_sdio from mmc_rescan+0x1d8/0x2a4
     mmc_rescan from process_scheduled_works+0x2bc/0x45c

> --- a/drivers/mmc/host/renesas_sdhi_core.c
> +++ b/drivers/mmc/host/renesas_sdhi_core.c
> @@ -235,9 +238,18 @@ static void renesas_sdhi_set_clock(struct tmio_mmc_host *host,
>
>         clock = clk & CLK_CTL_DIV_MASK;
>         if (clock != CLK_CTL_DIV_MASK)
> -               host->mmc->actual_clock /= (1 << (ffs(clock) + 1));
> +               host->mmc->actual_clock /= (1 << (ffs(clk) + 1));

Is this change intentional?

    clock = 0, ffs(clock) = 0
    clk = 8388608, ffs(clk) = 24

Later:

    static void tmio_mmc_max_busy_timeout(struct tmio_mmc_host *host)
    {
            unsigned int clk_rate = host->mmc->actual_clock ?: host->mmc->f_max;

            host->mmc->max_busy_timeout = host->get_timeout_cycles(host) /
                                          (clk_rate / MSEC_PER_SEC);

clk_rate = 2, BOOM!

   }

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds