linux-kernel - Re: [RFC 4/8] usb: phy: move TCSR driver into new file

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Date:	Thu, 19 May 2016 14:08:43 -0500
From:	Andy Gross <andy.gross@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Felipe Balbi <balbi@...nel.org>,
	David Brown <david.brown@...aro.org>,
	Peter Chen <Peter.Chen@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Mark Brown <broonie@...nel.org>,
	Bjorn Andersson <bjorn.andersson@...aro.org>,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>,
	linux-soc@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [RFC 4/8] usb: phy: move TCSR driver into new file

On 18 May 2016 at 16:24, Arnd Bergmann <arnd@...db.de> wrote:

<snip>

> +/*
> + * This abstracts the TCSR register area in Qualcomm SoCs, originally
> + * introduced by Tim Bird as part of the phy-msm-usb.ko device driver,
> + * and split out by Arnd Bergmann into a separate file.
> + *
> + * This file shouldn't really exist, since we have no way to detect
> + * if the TCSR actually exists in the hardcoded location, or if it
> + * is compatible with the version that was originally used.
> + *
> + * If the assumptions ever change, we have to come up with a better
> + * solution.
> + */
> +#include <linux/module.h>
> +#include <linux/io.h>
> +
> +/* USB phy selector - in TCSR address range */
> +#define USB2_PHY_SEL         0xfd4ab000
> +
> +/*
> + * qcom_tcsr_phy_sel -- Select secondary PHY via TCSR
> + *
> + * Select the secondary PHY using the TCSR register, if phy-num=1
> + * in the DTS (or phy_number is set in the platform data).  The
> + * SOC has 2 PHYs which can be used with the OTG port, and this
> + * code allows configuring the correct one.
> + *
> + * Note: This resolves the problem I was seeing where I couldn't
> + * get the USB driver working at all on a dragonboard, from cold
> + * boot.  This patch depends on patch 5/14 from Ivan's msm USB
> + * patch set.  It does not use DT for the register address, as
> + * there's no evidence that this address changes between SoC
> + * versions.
> + *             - Tim
> + */
> +int qcom_tcsr_phy_sel(u32 val)
> +{
> +       void __iomem *phy_select;
> +       int ret;
> +
> +       phy_select = ioremap(USB2_PHY_SEL, 4);
> +
> +       if (!phy_select) {
> +               ret = -ENOMEM;
> +               goto out;
> +       }
> +       /* Enable second PHY with the OTG port */
> +       writel(0x1, phy_select);
> +       ret = 0;
> +out:
> +       iounmap(phy_select);
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(qcom_tcsr_phy_sel);

I'd rather do something like what we did for the GSBI.  It needed to
change some phy related bits in the TCSR as well.  We defined the TCSR
as a syscon, with binding documentation under mfd.  If we add a syscon
entry and use it if it is present, we can deal with that pretty
easily.  The offsets change for each soc, and this would also fix that
issue because we can change offset based on tcsr compat.

Regards,

Andy