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Message-ID: <2d3d529e006a6fbef6fe4a8a20b3eb23fa476ff7.camel@xry111.site>
Subject: Re: [PATCH v8 4/4] riscv: dts: thead: Enable LicheePi 4A eMMC and
 microSD
From: Xi Ruoyao <xry111@xry111.site>
To: Maxim Kiselev <bigunclemax@gmail.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>, Conor Dooley <conor@kernel.org>, 
 devicetree@vger.kernel.org, dfustini@baylibre.com, guoren@kernel.org, 
 jkridner@beagleboard.org, jszhang@kernel.org, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@linaro.org>, open list
 <linux-kernel@vger.kernel.org>,  linux-riscv@lists.infradead.org, Palmer
 Dabbelt <palmer@dabbelt.com>, Paul Walmsley <paul.walmsley@sifive.com>,
 robertcnelson@beagleboard.org, Rob Herring <robh+dt@kernel.org>, 
 wefu@redhat.com
Date: Wed, 20 Mar 2024 20:52:13 +0800
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	<CALHCpMhc1F5Ue7U_gsDXREHUZRVQJNYRCJxYxoNqbN=-39jf7A@mail.gmail.com>
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On Wed, 2024-03-20 at 15:28 +0300, Maxim Kiselev wrote:
> Hi Xi, Drew
>=20
> I have the same problem with SD on my LicheePi 4A.
>=20
> 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.
>=20
> 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)
>=20
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 /* perform tuning */
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 sdhci_start_tuning(host);
> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 host->tuning_loop_count =3D 128:
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 host->tuning_err =3D __sdhci_e=
xecute_tuning(host, opcode);
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (host->tuning_err) {
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 /* disable auto-tuning upon tuning error */
>=20
> After that change tuning works fine. The same value of loop count is
> used in RevyOS BSP
> https://github.com/revyos/thead-kernel/blob/c6d4e5df18a17903d012ffd89e67d=
0ee5ce6cf2d/drivers/mmc/host/sdhci-of-dwcmshc.c#L185
>=20
> Honestly, it looks a little bit strange for me.
>=20
> 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).
>=20
> 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 :(.

--=20
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University