Re: [PATCH v4 01/13] phy: usb: EHCI DMA may lose a burst of DMA data for 7255xA0 family

From: Florian Fainelli
Date: Fri Jan 03 2020 - 13:22:59 EST

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@xxxxxxxxx>

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