linux-kernel - RE: [PATCH v6 5/6] usb:cdns3 Add Cadence USB3 DRD Driver

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Message-ID: <BYAPR07MB47099815FA4691B6106F80FEDD150@BYAPR07MB4709.namprd07.prod.outlook.com>
Date:   Tue, 4 Jun 2019 08:17:34 +0000
From:   Pawel Laszczak <pawell@...ence.com>
To:     Sekhar Nori <nsekhar@...com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "felipe.balbi@...ux.intel.com" <felipe.balbi@...ux.intel.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>,
        "heikki.krogerus@...ux.intel.com" <heikki.krogerus@...ux.intel.com>,
        "andy.shevchenko@...il.com" <andy.shevchenko@...il.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "rogerq@...com" <rogerq@...com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "jbergsagel@...com" <jbergsagel@...com>, "nm@...com" <nm@...com>,
        Suresh Punnoose <sureshp@...ence.com>,
        "peter.chen@....com" <peter.chen@....com>,
        Rahul Kumar <kurahul@...ence.com>
Subject: RE: [PATCH v6 5/6] usb:cdns3 Add Cadence USB3 DRD Driver

>
>On 10/04/19 1:18 PM, Pawel Laszczak wrote:
>> +static void cdns3_wa1_tray_restore_cycle_bit(struct cdns3_device *priv_dev,
>> +					     struct cdns3_endpoint *priv_ep)
>> +{
>> +	int dma_index;
>> +	u32 doorbell;
>> +
>> +	doorbell = !!(readl(&priv_dev->regs->ep_cmd) & EP_CMD_DRDY);
>
>> +	dma_index = (readl(&priv_dev->regs->ep_traddr) -
>> +		    priv_ep->trb_pool_dma) / TRB_SIZE;
>
>This gets upgraded to 64-bit by 64-bit division whenever dma_addr_t is
>64-bit. That should be avoided. Following diff should fix it.
>But please review the logic itself. You are subtracting a 64 bit entity
>from a 32-bit entity. What is guaranteeing that priv_ep->trb_pool_dma is
>32-bit?
>
>There is one more instance of same issue in cdns3_request_handled().
>
>Thanks,
>Sekhar
>
>[1]
>diff --git a/drivers/usb/cdns3/gadget.c b/drivers/usb/cdns3/gadget.c
>index bfd5dbf40c7e..e73b618501fb 100644
>--- a/drivers/usb/cdns3/gadget.c
>+++ b/drivers/usb/cdns3/gadget.c
>@@ -749,8 +749,8 @@ static void cdns3_wa1_tray_restore_cycle_bit(struct cdns3_device *priv_dev,
> 	u32 doorbell;
>
> 	doorbell = !!(readl(&priv_dev->regs->ep_cmd) & EP_CMD_DRDY);
>-	dma_index = (readl(&priv_dev->regs->ep_traddr) -
>-		    priv_ep->trb_pool_dma) / TRB_SIZE;
>+	dma_index = readl(&priv_dev->regs->ep_traddr) - priv_ep->trb_pool_dma;
>+	dma_index /= TRB_SIZE;

Hi Sekhar,

In the next latest version I added setting dma and coherent mask to 32-bits as suggested by Roger. 
Controller can do only 32-bit access.

DMA address space should be allocated from first 32 bits of address space. Most significant 32-bit 
of priv_ep->trb_pool_dma should be zeroed, so I do not assume any issue in this place.

Have you seen any issue with this on your platform ?

Thanks,
Pawel,