linux-kernel - Re: [PATCH v2] memory: renesas-rpc-if: Fix PHYCNT.STRTIM setting

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Message-ID: <CAMuHMdXY0c4qKCi057CtJdhUJ+443rtyCjwYyK3qGgwWTZ2a0A@mail.gmail.com>
Date:   Thu, 26 Jan 2023 10:39:50 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc:     linux-renesas-soc@...r.kernel.org,
        Prabhakar <prabhakar.csengg@...il.com>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] memory: renesas-rpc-if: Fix PHYCNT.STRTIM setting

"Hi Wolfram,

On Wed, Jan 18, 2023 at 12:38 PM Wolfram Sang
<wsa+renesas@...g-engineering.com> wrote:
> From: Cong Dang <cong.dang.xn@...esas.com>
>
> According to the datasheets, the Strobe Timing Adjustment bit (STRTIM)
> setting is different on R-Car SoCs, i.e.
>
> R-Car H3 ES1.*  : STRTIM[2:0] is set to 0x0
> R-Car M3 ES1.*  : STRTIM[2:0] is set to 0x6
> other R-Car Gen3: STRTIM[2:0] is set to 0x7
> other R-Car Gen4: STRTIM[3:0] is set to 0xf
>
> To fix this issue, a DT match data was added to specify the setting
> for special use cases.
>
> Signed-off-by: Cong Dang <cong.dang.xn@...esas.com>
> Signed-off-by: Hai Pham  <hai.pham.ud@...esas.com>
> [wsa: rebased, restructured a little, added Gen4 support]
> Signed-off-by: Wolfram Sang <wsa+renesas@...g-engineering.com>
> ---
>
> Change since V1:
>
> * use proper mask when updating STRTIM bits (thanks, Geert!)

Thanks for the update!

> --- a/drivers/memory/renesas-rpc-if.c
> +++ b/drivers/memory/renesas-rpc-if.c

> @@ -163,6 +165,36 @@ static const struct regmap_access_table rpcif_volatile_table = {
>         .n_yes_ranges   = ARRAY_SIZE(rpcif_volatile_ranges),
>  };
>
> +static const struct rpcif_info rpcif_info_r8a7795_es1 = {
> +       .type = RPCIF_RCAR_GEN3,
> +       .strtim = 0,
> +};
> +
> +static const struct rpcif_info rpcif_info_r8a7796_es1 = {
> +       .type = RPCIF_RCAR_GEN3,
> +       .strtim = 6,
> +};
> +
> +static const struct rpcif_info rpcif_info_gen3 = {
> +       .type = RPCIF_RCAR_GEN3,
> +       .strtim = 7,
> +};
> +
> +static const struct rpcif_info rpcif_info_rz_g2l = {
> +       .type = RPCIF_RZ_G2L,
> +       .strtim = 7,
> +};
> +
> +static const struct rpcif_info rpcif_info_gen4 = {
> +       .type = RPCIF_RCAR_GEN4,
> +       .strtim = 15,
> +};
> +
> +static const struct soc_device_attribute rpcif_info_match[]  = {
> +       { .soc_id = "r8a7795", .revision = "ES1.*", .data = &rpcif_info_r8a7795_es1 },
> +       { .soc_id = "r8a7796", .revision = "ES1.*", .data = &rpcif_info_r8a7796_es1 },

As we do have a separate compatible value for R-Car M3-W+ aka R-Car M3-W ES3.0
("renesas,r8a77961-rpc-if"), and there is no R-Car M3-W ES2.x (see the PRR
screwup handling in renesas_soc_init()), you can just match against
"renesas,r8a7796-rpc-if instead.

> +       { /* Sentinel. */ }
> +};
>
>  /*
>   * Custom accessor functions to ensure SM[RW]DR[01] are always accessed with

> @@ -321,12 +360,10 @@ int rpcif_hw_init(struct rpcif *rpc, bool hyperflash)
>         /* DMA Transfer is not supported */
>         regmap_update_bits(rpc->regmap, RPCIF_PHYCNT, RPCIF_PHYCNT_HS, 0);
>
> -       if (rpc->type == RPCIF_RCAR_GEN3)
> -               regmap_update_bits(rpc->regmap, RPCIF_PHYCNT,
> -                                  RPCIF_PHYCNT_STRTIM(7), RPCIF_PHYCNT_STRTIM(7));:q

> -       else if (rpc->type == RPCIF_RCAR_GEN4)
> -               regmap_update_bits(rpc->regmap, RPCIF_PHYCNT,
> -                                  RPCIF_PHYCNT_STRTIM(15), RPCIF_PHYCNT_STRTIM(15));
> +       regmap_update_bits(rpc->regmap, RPCIF_PHYCNT,
> +                          /* create mask with all affected bits set */
> +                          RPCIF_PHYCNT_STRTIM(BIT(fls(rpc->info->strtim)) - 1),

fls(0) = 0, and BIT(-1) is undefined, so this won't work for R-Car
H3 ES1.x.  So I'm afraid you cannot handle this without storing the
actual mask ;-)

However, that issue will be moot as soon as we drop upstream support
for R-Car H3 ES1.x.  I cannot test RPC on R-Car H3 ES1.x anyway, as
the RPC is locked by TF/A, and the firmware cannot be upgraded easily
due to lack of upstream TF/A support for R-Car H3 ES1.x

> +                          RPCIF_PHYCNT_STRTIM(rpc->info->strtim));
>
>         regmap_update_bits(rpc->regmap, RPCIF_PHYOFFSET1, RPCIF_PHYOFFSET1_DDRTMG(3),
>                            RPCIF_PHYOFFSET1_DDRTMG(3));

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds