On Wed, 2024-03-20 at 15:28 +0300, Maxim Kiselev wrote:
> Hi Xi, Drew
>
> I have the same problem with SD on my LicheePi 4A.
>
> After some investigations I found how to fix this tuning error.
> Here is the patch that increases tuning loop count from
> 40(MAX_TUNING_LOOP at sdhci.c) to 128.
>
> diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c
> b/drivers/mmc/host/sdhci-of-dwcmshc.c
> index 8d6cfb648096..da8f5820fb69 100644
> --- a/drivers/mmc/host/sdhci-of-dwcmshc.c
> +++ b/drivers/mmc/host/sdhci-of-dwcmshc.c
> @@ -706,6 +706,7 @@ static int th1520_execute_tuning(struct sdhci_host
> *host, u32 opcode)
>
> /* perform tuning */
> sdhci_start_tuning(host);
> + host->tuning_loop_count = 128:
> host->tuning_err = __sdhci_execute_tuning(host, opcode);
> if (host->tuning_err) {
> /* disable auto-tuning upon tuning error */
>
> After that change tuning works fine. The same value of loop count is
> used in RevyOS BSP
> https://github.com/revyos/thead-kernel/blob/c6d4e5df18a17903d012ffd89e67d0ee5ce6cf2d/drivers/mmc/host/sdhci-of-dwcmshc.c#L185
>
> Honestly, it looks a little bit strange for me.
>
> It seems that the tuning algorithm requires to move through
> all the taps of delay line(128 taps?) even if we use THRESHOLD_MODE
> instend LARGEST_WIN_MODE (I mean bit 2 in AT_CTRL_R(0x540) register).
>
> Xi, could you also test my fix on your board?
I'll try it this weekend. Now having some work with "real time
priority" to do :(.
--
Xi Ruoyao <xry111@xxxxxxxxxxx>
School of Aerospace Science and Technology, Xidian University
