[PATCH 5/5] dma: ti: k3-udma: invalidate prepared buffers before pushing to recv ring

[Sverdlin, Alexander]

Hello Matthias,

On Fri, 2024-04-26 at 10:02 +0200, Matthias Schiffer wrote:
> Buffers must not have an unclean cache before being used for DMA - a
> pending write-back may corrupt the next dev-to-mem transfer otherwise.
> 
> This was consistently noticeable during long TFTP transfers, when an ARP
> request is answered by U-Boot in the middle of the transfer:
> 
> As U-Boot's arp_receive() reuses the receive buffer to prepare its
> reply packet, the beginning of one of the next incoming TFTP packets
> is overwritten by the ARP reply. The corrupted packet is ignored, but
> the TFTP transfer stalls for a few seconds until a timeout is detected
> and a retransmit is triggered.
> 
> Signed-off-by: Matthias Schiffer <matthias.schiffer at ew.tq-group.com>

thanks for the series! I've tested it on a custom AM625-based board
issuing a a couple of pings:

am65_cpsw_nuss ethernet at 8000000: K3 CPSW: nuss_ver: 0x6BA01103 cpsw_ver: 0x6BA81103 ale_ver: 0x00290105 Ports:2
Net:   eth0: ethernet at 8000000port@1
Autobooting in 3 seconds, press "<Esc><Esc>" to stop
U-Boot# ping 192.168.251.10
ti-udma dma-controller at 485c0000: k3_dmaring Ring probed rings:150, sci-dev-id:30
ti-udma dma-controller at 485c0000: dma-ring-reset-quirk: disabled
am65_cpsw_nuss_port ethernet at 8000000port@1: K3 CPSW: rflow_id_base: 19
link up on port 1, speed 100, full duplex
Using ethernet at 8000000port@1 device
host 192.168.251.10 is alive
U-Boot# ping 192.168.251.10
am65_cpsw_nuss_port ethernet at 8000000port@1: K3 CPSW: rflow_id_base: 19
link up on port 1, speed 100, full duplex
Using ethernet at 8000000port@1 device
host 192.168.251.10 is alive

This sequence looks exactly the same with your patches and without.
Therefore for the whole series:

Tested-by: Alexander Sverdlin <alexander.sverdlin at siemens.com>

> ---
>  drivers/dma/ti/k3-udma.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c
> index 4e6f7f570c5..8f6d396653e 100644
> --- a/drivers/dma/ti/k3-udma.c
> +++ b/drivers/dma/ti/k3-udma.c
> @@ -2678,6 +2678,9 @@ int udma_prepare_rcv_buf(struct dma *dma, void *dst, size_t size)
>         cppi5_hdesc_set_pktlen(desc_rx, size);
>         cppi5_hdesc_attach_buf(desc_rx, dma_dst, size, dma_dst, size);
>  
> +       invalidate_dcache_range((unsigned long)dma_dst,
> +                               (unsigned long)(dma_dst + size));
> +
>         flush_dcache_range((unsigned long)desc_rx,
>                            ALIGN((unsigned long)desc_rx + uc->config.hdesc_size,
>                                  ARCH_DMA_MINALIGN));

-- 
Alexander Sverdlin
Siemens AG
www.siemens.com