linux-kernel - Re: [PATCH v3 7/7] usb: musb: jz4740: Disable pullup at init

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Date:   Tue, 10 Dec 2019 13:52:30 -0600
From:   Bin Liu <b-liu@...com>
To:     Paul Cercueil <paul@...pouillou.net>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>, <od@...c.me>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 7/7] usb: musb: jz4740: Disable pullup at init

Hi,

On Tue, Dec 10, 2019 at 06:11:10PM +0100, Paul Cercueil wrote:
> The pullup may be already enabled before the driver is initialized.
> It has to be disabled at init time, as we cannot guarantee that a gadget
> driver will be bound to the UDC.
> 
> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
> 
> Notes:
>     v3: New patch
> 
>  drivers/usb/musb/jz4740.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/usb/musb/jz4740.c b/drivers/usb/musb/jz4740.c
> index f948eca654f3..1af9e4053312 100644
> --- a/drivers/usb/musb/jz4740.c
> +++ b/drivers/usb/musb/jz4740.c
> @@ -75,6 +75,7 @@ static const struct musb_hdrc_config jz4740_musb_config = {
>  static int jz4740_musb_init(struct musb *musb)
>  {
>  	struct device *dev = musb->controller->parent;
> +	u8 power;
>  	int err;
>  
>  	if (dev->of_node)
> @@ -97,6 +98,14 @@ static int jz4740_musb_init(struct musb *musb)
>  	musb->isr = jz4740_musb_interrupt;
>  	musb->dma_share_usb_irq = true;
>  
> +	/*
> +	 * If the SoC booted from USB the pullup might still be set.
> +	 * Disable it until a gadget is bound.
> +	 */
> +	power = musb_readb(musb->mregs, MUSB_POWER);
> +	power &= ~MUSB_POWER_SOFTCONN;
> +	musb_writeb(musb->mregs, MUSB_POWER, power);
> +
>  	return 0;
>  }

It is preferred the glue drivers don't touch the controller core
registers if possible. Please try the following patch instead.

-Bin.

------------- >8 ------------
t a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
index 683b719c5026..2f9105e8ea38 100644
--- a/drivers/usb/musb/musb_core.c
+++ b/drivers/usb/musb/musb_core.c
@@ -2317,6 +2317,9 @@ musb_init_controller(struct device *dev, int nIrq, void __iomem *ctrl)
        musb_disable_interrupts(musb);
        musb_writeb(musb->mregs, MUSB_DEVCTL, 0);

+       /* MUSB_POWER_SOFTCONN might be already set, jz4740 does this. */
+       musb_writeb(musb->mregs, MUSB_POWER, 0);
+
        /* Init IRQ workqueue before request_irq */
        INIT_DELAYED_WORK(&musb->irq_work, musb_irq_work);
        INIT_DELAYED_WORK(&musb->deassert_reset_work, musb_deassert_reset);