From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-i2c-owner@vger.kernel.org>
Date: Fri, 29 Jun 2018 09:54:04 +0200
From: Wolfram Sang <wsa@the-dreams.de>
To: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Wolfram Sang <wsa+renesas@sang-engineering.com>,
        Linux I2C <linux-i2c@vger.kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Subject: Re: [PATCH 1/1] i2c: rcar: handle RXDMA HW behaviour on Gen3
Message-ID: <20180629075404.ivnaauv2hdir32ig@ninjato>
References: <20180628204538.866-1-wsa+renesas@sang-engineering.com>
 <20180628204538.866-2-wsa+renesas@sang-engineering.com>
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> > +       /* Gen3 needs a reset before allowing RXDMA once */
> > +       if (priv->devtype =3D=3D I2C_RCAR_GEN3) {
>=20
> So on R-Car Gen3 the device is always reset, even if no reads will be don=
e?
> Or is that something you cannot check for at this point?

You got a point. I copied the behaviour from the BSP to do this as early
as possible. Still, it might be worthwhile to merge this into
rcar_i2c_request_dma() and move the call to it to the front. Will check.

> > +       if (priv->devtype =3D=3D I2C_RCAR_GEN3) {
> > +               priv->rstc =3D devm_reset_control_get_exclusive(&pdev->=
dev, NULL);
> > +               if (!IS_ERR(priv->rstc)) {
> > +                       ret =3D reset_control_status(priv->rstc);
>=20
> Why this call and check? To check if .status() is implemented (it always =
is
> on R-Car Gen3, if CONFIG_RESET_CONTROLLER is enabled), and to avoid the
> timeout in rcar_i2c_do_reset() on every transfer?

Yes. We can save all the hazzle if it is not implemented. And I didn't
want to implicitly assume that it will be implemented anywhere forever.
That could be a very subtle bug later.

Thanks,

   Wolfram


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