linux-kernel - Re: [PATCH v8 4/4] riscv: dts: thead: Enable LicheePi 4A eMMC and microSD

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Date: Wed, 20 Mar 2024 20:52:13 +0800
From: Xi Ruoyao <xry111@...111.site>
To: Maxim Kiselev <bigunclemax@...il.com>
Cc: Albert Ou <aou@...s.berkeley.edu>, Conor Dooley <conor@...nel.org>, 
 devicetree@...r.kernel.org, dfustini@...libre.com, guoren@...nel.org, 
 jkridner@...gleboard.org, jszhang@...nel.org, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@...aro.org>, open list
 <linux-kernel@...r.kernel.org>,  linux-riscv@...ts.infradead.org, Palmer
 Dabbelt <palmer@...belt.com>, Paul Walmsley <paul.walmsley@...ive.com>,
 robertcnelson@...gleboard.org, Rob Herring <robh+dt@...nel.org>, 
 wefu@...hat.com
Subject: Re: [PATCH v8 4/4] riscv: dts: thead: Enable LicheePi 4A eMMC and
 microSD

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@...111.site>
School of Aerospace Science and Technology, Xidian University