[PATCH 4/6] mmc: host: sdhci-esdhc-imx.c: correct the auto-tuning setting for sdio device

[Ulf Hansson]

On Mon, 16 Aug 2021 at 15:00, <haibo.chen at nxp.com> wrote:
>
> From: Haibo Chen <haibo.chen at nxp.com>
>
> USDHC contain auto tuning circuit, this circuit will work automatically after
> the tuning procedurae, it can increase/decrease the delay cell according to
> the outside environment change (like temperature).
>
> Unfortunately, this auto tuning circuit can not handle the async sdio device
> interrupt correctly. When sdio device use 4 data line, async sdio interrupt
> will use DAT[1], if we enable auto tuning circuit check 4 data lines, include
> the DAT[1], this circuit will detect this interrupt, take this as a data on
> DAT[1], and adjust the delay cell wrongly.
>
> This is the hardware design limitation, to avoid this, when sdio device enable
> async interrupt, auto tuning circuit only check DAT[0] and CMD lines.

SDIO irqs are being enabled/disabled dynamically in runtime by the mmc
core via the host ops ->enable_sdio_irq().

Rather than forcing the autotuning circuit to stay unused statically,
perhaps an option would be to disable it when the SDIO irqs becomes
enabled? Or maybe that becomes too complicated?

>
> Signed-off-by: Haibo Chen <haibo.chen at nxp.com>
> ---
>  drivers/mmc/host/sdhci-esdhc-imx.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index f18d169bc8ff..ab84c29777e5 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -226,6 +226,7 @@ struct esdhc_platform_data {
>         unsigned int tuning_step;       /* The delay cell steps in tuning procedure */
>         unsigned int tuning_start_tap;  /* The start delay cell point in tuning procedure */
>         unsigned int strobe_dll_delay_target;   /* The delay cell for strobe pad (read clock) */
> +       bool sdio_async_interrupt_enabled;      /* sdio device enable the async interrupt */
>  };
>
>  struct esdhc_soc_data {
> @@ -416,6 +417,8 @@ static inline void esdhc_wait_for_card_clock_gate_off(struct sdhci_host *host)
>  /* Enable the auto tuning circuit to check the CMD line and BUS line */
>  static inline void usdhc_auto_tuning_mode_sel(struct sdhci_host *host)
>  {
> +       struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +       struct pltfm_imx_data *imx_data = sdhci_pltfm_priv(pltfm_host);
>         u32 buswidth, auto_tune_buswidth;
>
>         buswidth = USDHC_GET_BUSWIDTH(readl(host->ioaddr + SDHCI_HOST_CONTROL));
> @@ -432,6 +435,18 @@ static inline void usdhc_auto_tuning_mode_sel(struct sdhci_host *host)
>                 break;
>         }
>
> +       /*
> +        * If sdio device use async interrupt, it will use DAT[1] to signal
> +        * the device's interrupt asynchronous when use 4 data lines.
> +        * Then hardware auto tuning circuit MUST NOT check the DAT[1] line,
> +        * otherwise auto tuning will be impacted by this async interrupt,
> +        * and change the delay cell incorrectly, which then cause data/cmd
> +        * errors.
> +        * This is the hardware auto tuning circuit limitation.
> +        */
> +       if (imx_data->boarddata.sdio_async_interrupt_enabled)
> +               auto_tune_buswidth = ESDHC_VEND_SPEC2_AUTO_TUNE_1BIT_EN;
> +
>         esdhc_clrset_le(host, ESDHC_VEND_SPEC2_AUTO_TUNE_MODE_MASK,
>                         auto_tune_buswidth | ESDHC_VEND_SPEC2_AUTO_TUNE_CMD_EN,
>                         ESDHC_VEND_SPEC2);
> @@ -1531,6 +1546,9 @@ sdhci_esdhc_imx_probe_dt(struct platform_device *pdev,
>         if (of_property_read_u32(np, "fsl,delay-line", &boarddata->delay_line))
>                 boarddata->delay_line = 0;
>
> +       if (of_property_read_bool(np, "fsl,sdio-async-interrupt-enabled"))

As stated on the DT patch, I think you can use the "cap-sdio-irq" instead.

> +               boarddata->sdio_async_interrupt_enabled = true;
> +
>         mmc_of_parse_voltage(host->mmc, &host->ocr_mask);
>
>         if (esdhc_is_usdhc(imx_data) && !IS_ERR(imx_data->pinctrl)) {
> --
> 2.17.1
>

Kind regards
Uffe