From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean-Francois Moine Subject: Re: [PATCH v2 1/2] ASoC: kirkwood: clk: probe defer when clock not yet ready Date: Sat, 21 Sep 2013 19:06:24 +0200 Message-ID: <20130921190624.1435c26b@armhf> References: <20130921120006.47b00fe7@armhf> <20130921104734.GJ12758@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20130921104734.GJ12758-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Russell King - ARM Linux Cc: Liam Girdwood , Mark Brown , Jaroslav Kysela , Takashi Iwai , Grant Likely , Rob Herring , alsa-devel-K7yf7f+aM1XWsZ/bQMPhNw@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Mike Turquette List-Id: devicetree@vger.kernel.org On Sat, 21 Sep 2013 11:47:34 +0100 Russell King - ARM Linux wrote: > On Sat, Sep 21, 2013 at 12:00:06PM +0200, Jean-Francois Moine wrote: > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c > > index a004769..582abc8 100644 > > --- a/drivers/clk/clk.c > > +++ b/drivers/clk/clk.c > > @@ -2181,7 +2181,7 @@ EXPORT_SYMBOL_GPL(of_clk_del_provider); > > struct clk *of_clk_get_from_provider(struct of_phandle_args *clksp= ec) > > { > > struct of_clk_provider *provider; > > - struct clk *clk =3D ERR_PTR(-ENOENT); > > + struct clk *clk =3D ERR_PTR(-EPROBE_DEFER); > > =20 > > /* Check if we have such a provider in our array */ > > mutex_lock(&of_clk_lock); > > diff --git a/drivers/clk/clkdev.c b/drivers/clk/clkdev.c > > index 442a313..f8b28d9 100644 > > --- a/drivers/clk/clkdev.c > > +++ b/drivers/clk/clkdev.c > > @@ -157,8 +157,13 @@ struct clk *clk_get(struct device *dev, const = char *con_id) > > =20 > > if (dev) { > > clk =3D of_clk_get_by_name(dev->of_node, con_id); > > - if (!IS_ERR(clk) && __clk_get(clk)) > > - return clk; > > + if (!IS_ERR(clk)) { > > + if (__clk_get(clk)) > > + return clk; > > + } else { > > + if (PTR_ERR(clk) =3D=3D -EPROBE_DEFER) > > + return clk; > > + } >=20 > Another comment. This is broken - it will never fall through if a > 'dev' is given, because of_clk_get_by_name() will always return an > -EPROBE_DEFER error pointer in that case. >=20 > So this approach is unworkable. > And another comment: >=20 > This whole approach is broken - while Mark is correct that we should > find a way to return -EPROBE_DEFER if a clock is specified, the solut= ion > here does not allow that - it will return -EPROBE_DEFER whenever the > clock is not found _or_ is not specified. >=20 > This has the effect of making the external clock *non*optional for th= e > kirkwood-i2s driver, which is also completely broken. It works fine for me (I tried both cases, with and without the external clock). The scheme is as follows: - kirkwood-i2s kirkwood_i2s_dev_probe() calls: priv->extclk =3D &pdev->dev, "extclk"); - devm_clk_get() calls: clk =3D clk_get(dev, id); - clk_get() does: if (dev) // this is the case clk =3D of_clk_get_by_name(dev->of_node, con_id); - of_clk_get_by_name() does: if (name) // this is the case index =3D of_property_match_string(np, "clock-names", name); Here, if the external clock is declared in the DT, index is >=3D 0. If there is no externel clock in the DT, index is < 0. clk =3D of_clk_get(np, index); if (!IS_ERR(clk)) break; else if (name && index >=3D 0) { pr_err("ERROR: could not get clock %s:%s(%i)\n", np->full_name, name ? name : "", index); =20 return clk; } - If the index is < 0, of_clk_get() immediately returns -EINVAL. So, kirkwood-i2s knows there is no external clock. DONE. - otherwise, if the index is >=3D 0 (the external clock is declared in the DT), of_clk_get() gets the phandle (of_parse_phandle_with_args()) and gets the clock (of_clk_get_from_provider()). This last function returns either the clock (device initialized), a -EPROBE_DEFER error (clock not yet initialized) or some other error (bad DT or clock error). So, kirkwood-i2s knows there is a declared external clock and it acts according to the return code (accept, defer or ignore). DONE. Did I miss something? --=20 Ken ar c'henta=C3=B1 | ** Breizh ha Linux atav! ** Jef | http://moinejf.free.fr/ -- To unsubscribe from this list: send the line "unsubscribe devicetree" i= n the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html