linux-kernel - Re: [PATCH v2 1/5] phy: Add new Exynos USB PHY driver

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Date:	Mon, 28 Oct 2013 21:00:01 +0100
From:	Tomasz Figa <tomasz.figa@...il.com>
To:	Kamil Debski <k.debski@...sung.com>
Cc:	'Kishon Vijay Abraham I' <kishon@...com>,
	linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
	linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm@...r.kernel.org, kyungmin.park@...sung.com,
	Tomasz Figa <t.figa@...sung.com>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	gautam.vivek@...sung.com, mat.krawczuk@...il.com
Subject: Re: [PATCH v2 1/5] phy: Add new Exynos USB PHY driver

Hi Kamil,

On Monday 28 of October 2013 14:52:19 Kamil Debski wrote:
> Hi Kishon,
> 
> Thank you for your review! I will answer your comments below.
[snip]
> > > +
> > > +	switch (drv->cfg->cpu) {
> > > +	case TYPE_EXYNOS4210:
> > 
> > > +	case TYPE_EXYNOS4212:
> > Lets not add such cpu checks inside driver.
> 
> Some SoC have a special register, which switches the OTG lines between
> device and host modes. I understand that it might not be the prettiest
> code. I see this as a good compromise between having a single huge
> driver for all Exynos SoCs and having a multiple drivers for each SoC
> version. PHY IPs in these chips very are similar but have to be handled
> differently. Any other ideas to solve this issue?

Maybe adding a flag in drv->cfg called, for example, .has_mode_switch 
could solve this problem without having to check the SoC type explicitly?

[snip]
> > > +#ifdef CONFIG_PHY_EXYNOS4210_USB
> > 
> > Do we really need this?
> 
> No we don't. The driver can always support all Exynos SoC versions.
> These config options were added for flexibility.
> 
> > > +extern const struct uphy_config exynos4210_uphy_config; #endif
> > > +
> > > +#ifdef CONFIG_PHY_EXYNOS4212_USB
> > 
> > Same here.
> > 
> > > +extern const struct uphy_config exynos4212_uphy_config; #endif
> > > +
> > > +static const struct of_device_id exynos_uphy_of_match[] = { #ifdef
> > > +CONFIG_PHY_EXYNOS4210_USB
> > 
> > #if not needed here.
> 
> If the #ifdef CONFIG_PHY_EXYNOS4210_USB is removed then yes. Otherwise
> it is necessary - exynos4210_uphy_config may be undefined.

I believe this and other ifdefs below are needed, otherwise, with support
for one of the SoCs disabled, the driver could still bind to its 
compatible value.

Best regards,
Tomasz

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