[PATCH] ARM: dts: bcm283x: increase dwc2's RX FIFO size

[Stefan Wahren]

Hi Pavel,

Am 13.11.20 um 08:18 schrieb Pavel Hofman:
> The previous version of the dwc2 overlay set the RX FIFO size to
> 256 4-byte words. This is not enough for 1024 bytes of the largest
> isochronous high speed packet allowed, because it doesn't take into
> account extra space needed by dwc2.
>
> RX FIFO's size is calculated based on the following (in 4byte words):
> - 13 locations for SETUP packets
>   5*n + 8 for Slave and Buffer DMA mode where n is number of control
>   endpoints which is 1 on the bcm283x core
>
> - 1 location for Global OUT NAK
>
> - 2 * 257 locations for status information and the received packet.
>   Typically two spaces are recommended so that when the previous packet
>   is being transferred to AHB, the USB can receive the subsequent
>   packet.
>
> - 10 * 1 location for transfer complete status for last packet of each
>   endpoint. The bcm283x core has 5 IN and 5 OUT EPs
>
> - 10 * 1 additional location for EPDisable status for each endpoint
>
> - 5 * 2 additional locations are recommended for each OUT endpoint
>
> Total is 558 locations.
>
> Signed-off-by: Phil Elwell <phil at raspberrypi.com>
> Signed-off-by: Pavel Hofman <pavel.hofman at ivitera.com>
> ---
>  arch/arm/boot/dts/bcm283x-rpi-usb-otg.dtsi        | 2 +-
>  arch/arm/boot/dts/bcm283x-rpi-usb-peripheral.dtsi | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/boot/dts/bcm283x-rpi-usb-otg.dtsi
> b/arch/arm/boot/dts/bcm283x-rpi-usb-otg.dtsi
> index e2fd961..20322de 100644
> --- a/arch/arm/boot/dts/bcm283x-rpi-usb-otg.dtsi
> +++ b/arch/arm/boot/dts/bcm283x-rpi-usb-otg.dtsi
> @@ -1,7 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0
>  &usb {
>  	dr_mode = "otg";
> -	g-rx-fifo-size = <256>;
> +	g-rx-fifo-size = <558>;
>  	g-np-tx-fifo-size = <32>;
>  	/*
>  	 * According to dwc2 the sum of all device EP
> diff --git a/arch/arm/boot/dts/bcm283x-rpi-usb-peripheral.dtsi
> b/arch/arm/boot/dts/bcm283x-rpi-usb-peripheral.dtsi
> index 0ff0e9e..1409d1b 100644
> --- a/arch/arm/boot/dts/bcm283x-rpi-usb-peripheral.dtsi
> +++ b/arch/arm/boot/dts/bcm283x-rpi-usb-peripheral.dtsi
> @@ -1,7 +1,7 @@
>  // SPDX-License-Identifier: GPL-2.0
>  &usb {
>  	dr_mode = "peripheral";
> -	g-rx-fifo-size = <256>;
> +	g-rx-fifo-size = <558>;

sorry for being late at the party, but this change introduce a
regression on Raspberry Pi 4 B:

dwc2 fe980000.usb: dwc2_check_param_tx_fifo_sizes: Invalid parameter
g-tx-fifo-size, setting to default average

I known you didn't change the tx fifo size, but there are complex
constrains regarding the total fifo size.

Are you able to test this with a mainline kernel (not Raspberry Pi
kernel) and send a fix for this?

>  	g-np-tx-fifo-size = <32>;
>  	g-tx-fifo-size = <256 256 512 512 512 768 768>;
>  };