Re: Increasing stabilization time in sunxi_mmc_core_init

[Andre Przywara <andre.przywara@arm.com>]

On 21/07/2022 12:03, Da Xue wrote:

Hi Da,

> Users were reporting non-boot on our H5 boards (ALL-H3-CC-H5). u-boot
> gets stuck in SPL with this message for SD/eMMC respectively.
> 
> Trying to boot from MMC1 or Trying to boot from MMC2
> 
> I tested about 20 MicroSD cards from different brands and some were
> happy and some were not. Increasing the udelay to 8-10ms in
> drivers/mmc/sunxi_mmc.c sunxi_mmc_core_init after reset seems to fix
> the issue for the MicroSD cards.

That's interesting, thanks for the report. I don't remember hearing of 
issues with MMC before, at least not in the SPL.
It's a bit odd that waiting after the *controller* reset should affect 
SD cards, and 1ms seems plenty for just the reset.
I just checked and at least the SOFT_RESET and FIFO_RESET bits are self 
clearing. Can you try to use wait_for_bit_le32() to wait for those parts 
to finish? See sun8i_emac_eth_start() for an example.

And since you mentioned it's card related: can you check whether the 
delay is actually needed somewhere else, later? At some point where we 
wait to the card to response, for instance?

I am not against taking this patch, if it fixes problems for you, but 
just want to avoid that it papers over other issues.

Cheers,
Andre

> 
> Author: Da Xue <da@libre.computer>
> Date:   Wed Jul 20 19:11:55 2022 -0400
> 
>      sunxi: raise stabilization time for mmc from 1ms to 8ms
> 
> diff --git a/drivers/mmc/sunxi_mmc.c b/drivers/mmc/sunxi_mmc.c
> index 1bb7b6d0e9..499e057725 100644
> --- a/drivers/mmc/sunxi_mmc.c
> +++ b/drivers/mmc/sunxi_mmc.c
> @@ -297,7 +297,7 @@ static int sunxi_mmc_core_init(struct mmc *mmc)
> 
>          /* Reset controller */
>          writel(SUNXI_MMC_GCTRL_RESET, &priv->reg->gctrl);
> -       udelay(1000);
> +       udelay(8000);
> 
>          return 0;
>   }
> 
> I don't know the implications of this change so I am seeking feedback.
> Are other boards having this issue as well or is it specific to our
> hardware?
> 
> Best,
> Da
>