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Re: [PATCH v3 5/13] mmc: sunxi: Mask DATA0 when updating the clock

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  Re: [PATCH v3 5/13] mmc: sunxi: Mask DATA0 when updating the clock Ulf Hansson <ulf.hansson@linaro.org> - 2017-01-24 09:20 +0100
    Re: [PATCH v3 5/13] mmc: sunxi: Mask DATA0 when updating the clock Maxime Ripard <maxime.ripard@free-electrons.com> - 2017-01-25 10:20 +0100

#1565615 — Re: [PATCH v3 5/13] mmc: sunxi: Mask DATA0 when updating the clock

On 16 January 2017 at 17:56, Maxime Ripard
<maxime.ripard@free-electrons.com> wrote:
> The A64 MMC controllers need DATA0 to be masked while updating the clock,
> otherwise any subsequent command will result in a timeout.

Could you elaborate on what mask DATA0 really means? I don't follow.

Kind regards
Uffe

>
> Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
> ---
>  drivers/mmc/host/sunxi-mmc.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
> index 51d6388a194e..6bbe61397b7c 100644
> --- a/drivers/mmc/host/sunxi-mmc.c
> +++ b/drivers/mmc/host/sunxi-mmc.c
> @@ -101,6 +101,7 @@
>         (SDXC_SOFT_RESET | SDXC_FIFO_RESET | SDXC_DMA_RESET)
>
>  /* clock control bits */
> +#define SDXC_MASK_DATA0                        BIT(31)
>  #define SDXC_CARD_CLOCK_ON             BIT(16)
>  #define SDXC_LOW_POWER_ON              BIT(17)
>
> @@ -254,6 +255,9 @@ struct sunxi_mmc_cfg {
>         /* does the IP block support autocalibration? */
>         bool can_calibrate;
>
> +       /* Does DATA0 needs to be masked while the clock is updated */
> +       bool mask_data0;
> +
>         bool needs_new_timings;
>  };
>
> @@ -657,10 +661,12 @@ static int sunxi_mmc_oclk_onoff(struct sunxi_mmc_host *host, u32 oclk_en)
>         u32 rval;
>
>         rval = mmc_readl(host, REG_CLKCR);
> -       rval &= ~(SDXC_CARD_CLOCK_ON | SDXC_LOW_POWER_ON);
> +       rval &= ~(SDXC_CARD_CLOCK_ON | SDXC_LOW_POWER_ON | SDXC_MASK_DATA0);
>
>         if (oclk_en)
>                 rval |= SDXC_CARD_CLOCK_ON;
> +       if (host->cfg->mask_data0)
> +               rval |= SDXC_MASK_DATA0;
>
>         mmc_writel(host, REG_CLKCR, rval);
>
> @@ -680,6 +686,11 @@ static int sunxi_mmc_oclk_onoff(struct sunxi_mmc_host *host, u32 oclk_en)
>                 return -EIO;
>         }
>
> +       if (host->cfg->mask_data0) {
> +               rval = mmc_readl(host, REG_CLKCR);
> +               mmc_writel(host, REG_CLKCR, rval & ~SDXC_MASK_DATA0);
> +       }
> +
>         return 0;
>  }
>
> @@ -1081,6 +1092,7 @@ static const struct sunxi_mmc_cfg sun50i_a64_cfg = {
>         .idma_des_size_bits = 16,
>         .clk_delays = NULL,
>         .can_calibrate = true,
> +       .mask_data0 = true,
>         .needs_new_timings = true,
>  };
>
> --
> git-series 0.8.11

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#1566400

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On Tue, Jan 24, 2017 at 09:18:46AM +0100, Ulf Hansson wrote:
> On 16 January 2017 at 17:56, Maxime Ripard
> <maxime.ripard@free-electrons.com> wrote:
> > The A64 MMC controllers need DATA0 to be masked while updating the clock,
> > otherwise any subsequent command will result in a timeout.
> 
> Could you elaborate on what mask DATA0 really means? I don't follow.

To be honest, I don't really know :)

This is how it's called both in the vendor tree and the datasheet. I
*think* it might be the first data line on the bus, but I'm not sure
exactly why that would cause any issue when updating the clock.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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