linux-kernel - Re: [PATCH RFT 2/2] i2c: rcar: improve accuracy for R-Car Gen3+

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Message-ID: <ZQlrq68kQNWESkkC@shikoro>
Date:   Tue, 19 Sep 2023 11:36:43 +0200
From:   Wolfram Sang <wsa+renesas@...g-engineering.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     linux-renesas-soc@...r.kernel.org,
        Andi Shyti <andi.shyti@...nel.org>, linux-i2c@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFT 2/2] i2c: rcar: improve accuracy for R-Car Gen3+

Hi Geert,

> > +       u32 scl_gran;
> 
> You may want to store just u16 schd and scld instead, so you don't
> have to calculate them over and over again in rcar_i2c_init().
> They are calculated in rcar_i2c_clock_calculate() (called from .probe())
> anyway to validate ranges.
> 
> That would also avoid the need to come up with a better name for
> scl_gran ;-)

I like that idea! Will do.

> > +               /* Bail out if values don't fit into 16 bit or SMD became too large */
> > +               if (x * RCAR_SCLD_RATIO > 0xffff || RCAR_DEFAULT_SMD > x * RCAR_SCHD_RATIO)
> 
> The second part of the check looks wrong to me, as it would reject
> all the recommended register values for SMD and SCHD in the docs .
> 
> What does "SMD became too large" mean here?

Seems you clarified this on your own.

I will resend this series with the u16 variables and the cosmetic issues
fixed. And figure out how this slipped through my checkpatch hooks...

Thanks for the review!

   Wolfram


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