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

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Message-ID: <Y9J2oPHHNQoU+7m7@ninjato>
Date:   Thu, 26 Jan 2023 13:48:32 +0100
From:   Wolfram Sang <wsa+renesas@...g-engineering.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
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 Geert,

> > +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.

Right, I missed that! This is awesome news because with us dropping H3
ES1 support, this means we can drop all the soc_device_match() handling
now and use compatibles only. There, everybody happy :D

> > +       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 ;-)

You misread the parens, it is: BIT(0) - 1 = 0

I actually wrote a program to print out the calculations to make sure I
got it right. But yeah, ES1 is obsolete now.

I'll send V3 later today.

Thanks everyone,

   Wolfram


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