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Subject: Re: [PATCH v4 01/13] phy: usb: EHCI DMA may lose a burst of DMA data
 for 7255xA0 family
To:     Al Cooper <alcooperx@gmail.com>, linux-kernel@vger.kernel.org
Cc:     Kishon Vijay Abraham I <kishon@ti.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@broadcom.com>,
        Srinath Mannam <srinath.mannam@broadcom.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        "moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <linux-arm-kernel@lists.infradead.org>
References: <20200103181811.22939-1-alcooperx@gmail.com>
 <20200103181811.22939-2-alcooperx@gmail.com>
From:   Florian Fainelli <f.fainelli@gmail.com>
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Message-ID: <7f52c9eb-7cd6-db19-f67e-1d8e95621c4c@gmail.com>
Date:   Fri, 3 Jan 2020 10:22:54 -0800
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On 1/3/20 10:17 AM, Al Cooper wrote:
> When the EHCI controller received a 512 byte USB packet that
> had to be broken into 2 256 byte bursts across the SCB bus AND
> there was a following 512 byte USB packet, the second burst of
> data from the first packet was sometimes being lost. If the
> burst size was changed to 128 bytes via the EBR_SCB_SIZE field
> in the USB_CTRL_EBRIDGE register we'd see the 4th 128 byte burst
> of the first packet being lost. This problem became much worse
> if other threads were running that accessed memory, like a memcpy
> test. Setting the EBR_SCB_SIZE to 512, which prevents breaking
> the EHCI USB packet (max size of 512 bytes) into bursts, fixed
> the problem.
> 
> Signed-off-by: Al Cooper <alcooperx@gmail.com>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian