linux-kernel - Re: [PATCH v4 3/4] usb: ehci: Add new EHCI driver for Broadcom STB SoC's

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Message-ID: <Pine.LNX.4.44L0.2004291500390.19187-100000@netrider.rowland.org>
Date:   Wed, 29 Apr 2020 15:08:47 -0400 (EDT)
From:   Alan Stern <stern@...land.harvard.edu>
To:     Al Cooper <alcooperx@...il.com>
cc:     linux-kernel@...r.kernel.org,
        <bcm-kernel-feedback-list@...adcom.com>,
        <devicetree@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        <linux-usb@...r.kernel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Rob Herring <robh+dt@...nel.org>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v4 3/4] usb: ehci: Add new EHCI driver for Broadcom STB
 SoC's

On Wed, 29 Apr 2020, Al Cooper wrote:

> Add a new EHCI driver for Broadcom STB SoC's. A new EHCI driver
> was created instead of adding support to the existing ehci platform
> driver because of the code required to workaround bugs in the EHCI
> controller.
> 
> Signed-off-by: Al Cooper <alcooperx@...il.com>
> ---

...

> +static int __maybe_unused ehci_brcm_resume(struct device *dev)
> +{
> +	struct usb_hcd *hcd = dev_get_drvdata(dev);
> +	struct ehci_hcd *ehci = hcd_to_ehci(hcd);
> +	struct brcm_priv *priv = hcd_to_ehci_priv(hcd);
> +	int err;
> +
> +	err = clk_prepare_enable(priv->clk);
> +	if (err)
> +		return err;
> +	/*
> +	 * SWLINUX-1705: Avoid OUT packet underflows during high memory
> +	 *   bus usage
> +	 * port_status[0x0f] = Broadcom-proprietary USB_EHCI_INSNREG00
> +	 * @ 0x90
> +	 */
> +	ehci_writel(ehci, 0x00800040, &ehci->regs->port_status[0x10]);
> +	ehci_writel(ehci, 0x00000001, &ehci->regs->port_status[0x12]);
> +
> +	ehci_resume(hcd, false);
> +	return 0;
> +}

One extra thing that came to my attention recently...  Like all other
platform drivers, this has to set the runtime PM status of the
controller at the end of a system resume.  See

	https://marc.info/?l=linux-usb&m=158773611612885&w=2

for an example.

Alan Stern