[U-Boot] [PATCH v2] net/macb: increase RX buffer size for GEM

[Stefan Roese]

Hi Ramon,

On 14.07.19 17:25, Ramon Fried wrote:
> Macb Ethernet controller requires a RX buffer of 128 bytes. It is
> highly sub-optimal for Gigabit-capable GEM that is able to use
> a bigger DMA buffer. Change this constant and associated macros
> with data stored in the private structure.
> RX DMA buffer size has to be multiple of 64 bytes as indicated in
> DMA Configuration Register specification.
> 
> Signed-off-by: Ramon Fried <rfried.dev at gmail.com>

This patch breaks ethernet on my AT91SAM9G25 based board. With this
patch now, tftp does not complete the xfer any more:

=> tftp 21000000 big
ethernet at f802c000: PHY present at 1
ethernet at f802c000: Starting autonegotiation...
ethernet at f802c000: Autonegotiation complete
ethernet at f802c000: link up, 100Mbps full-duplex (lpa: 0xc5e1)
Using ethernet at f802c000 device
TFTP from server 192.168.1.5; our IP address is 192.168.1.249
Filename 'big'.
Load address: 0x21000000
Loading: #T T

With this patch reverted (as well as with v2019.07), tftp works
just fine.

I did not look into the patch yet. Perhaps you have a quick idea
on why this breaks my platform.

BTW: When I disable the dcache (dcache off), tftp also works fine
with this patch. So its definitely something cache / dma related.

Thanks,
Stefan

> ---
> v2: Fix multi-line comment style
>   drivers/net/macb.c | 30 ++++++++++++++++++++++--------
>   1 file changed, 22 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/macb.c b/drivers/net/macb.c
> index c072f99d8f..3c8b9722b3 100644
> --- a/drivers/net/macb.c
> +++ b/drivers/net/macb.c
> @@ -45,10 +45,17 @@
>   
>   DECLARE_GLOBAL_DATA_PTR;
>   
> -#define MACB_RX_BUFFER_SIZE		4096
> -#define MACB_RX_RING_SIZE		(MACB_RX_BUFFER_SIZE / 128)
> +/*
> + * These buffer sizes must be power of 2 and divisible
> + * by RX_BUFFER_MULTIPLE
> + */
> +#define MACB_RX_BUFFER_SIZE		128
> +#define GEM_RX_BUFFER_SIZE		2048
>   #define RX_BUFFER_MULTIPLE		64
> +
> +#define MACB_RX_RING_SIZE		32
>   #define MACB_TX_RING_SIZE		16
> +
>   #define MACB_TX_TIMEOUT		1000
>   #define MACB_AUTONEG_TIMEOUT	5000000
>   
> @@ -95,6 +102,7 @@ struct macb_device {
>   	void			*tx_buffer;
>   	struct macb_dma_desc	*rx_ring;
>   	struct macb_dma_desc	*tx_ring;
> +	size_t			rx_buffer_size;
>   
>   	unsigned long		rx_buffer_dma;
>   	unsigned long		rx_ring_dma;
> @@ -395,15 +403,16 @@ static int _macb_recv(struct macb_device *macb, uchar **packetp)
>   		}
>   
>   		if (status & MACB_BIT(RX_EOF)) {
> -			buffer = macb->rx_buffer + 128 * macb->rx_tail;
> +			buffer = macb->rx_buffer +
> +				macb->rx_buffer_size * macb->rx_tail;
>   			length = status & RXBUF_FRMLEN_MASK;
>   
>   			macb_invalidate_rx_buffer(macb);
>   			if (macb->wrapped) {
>   				unsigned int headlen, taillen;
>   
> -				headlen = 128 * (MACB_RX_RING_SIZE
> -						 - macb->rx_tail);
> +				headlen = macb->rx_buffer_size *
> +					(MACB_RX_RING_SIZE - macb->rx_tail);
>   				taillen = length - headlen;
>   				memcpy((void *)net_rx_packets[0],
>   				       buffer, headlen);
> @@ -701,7 +710,7 @@ static void gmac_configure_dma(struct macb_device *macb)
>   	u32 buffer_size;
>   	u32 dmacfg;
>   
> -	buffer_size = 128 / RX_BUFFER_MULTIPLE;
> +	buffer_size = macb->rx_buffer_size / RX_BUFFER_MULTIPLE;
>   	dmacfg = gem_readl(macb, DMACFG) & ~GEM_BF(RXBS, -1L);
>   	dmacfg |= GEM_BF(RXBS, buffer_size);
>   
> @@ -746,7 +755,7 @@ static int _macb_init(struct macb_device *macb, const char *name)
>   			paddr |= MACB_BIT(RX_WRAP);
>   		macb->rx_ring[i].addr = paddr;
>   		macb->rx_ring[i].ctrl = 0;
> -		paddr += 128;
> +		paddr += macb->rx_buffer_size;
>   	}
>   	macb_flush_ring_desc(macb, RX);
>   	macb_flush_rx_buffer(macb);
> @@ -957,8 +966,13 @@ static void _macb_eth_initialize(struct macb_device *macb)
>   	int id = 0;	/* This is not used by functions we call */
>   	u32 ncfgr;
>   
> +	if (macb_is_gem(macb))
> +		macb->rx_buffer_size = GEM_RX_BUFFER_SIZE;
> +	else
> +		macb->rx_buffer_size = MACB_RX_BUFFER_SIZE;
> +
>   	/* TODO: we need check the rx/tx_ring_dma is dcache line aligned */
> -	macb->rx_buffer = dma_alloc_coherent(MACB_RX_BUFFER_SIZE,
> +	macb->rx_buffer = dma_alloc_coherent(macb->rx_buffer_size * MACB_RX_RING_SIZE,
>   					     &macb->rx_buffer_dma);
>   	macb->rx_ring = dma_alloc_coherent(MACB_RX_DMA_DESC_SIZE,
>   					   &macb->rx_ring_dma);
>