[PATCH] Fix alignment issues with DMA TX on BCM4331

[Larry Finger]

On 08/12/2011 05:27 AM, David Woodhouse wrote:
> When the TX descriptor ring is not aligned to 8KiB on BCM4331, we have
> to write the full address to the TXINDEX register or the DMA engine gets
> confused after the first time we wrap round to slot zero.
>
> [ 7438.538945] Poked TX with address fe0 for slot 254
> [ 7438.539077] Acking gen reason 20000000
> [ 7438.539177] irq xmitstat 20fc1001 0000007f
> [ 7438.607861] Poked TX with address 0 for slot 0
> [ 7438.608567] Acking gen reason 20000000
> [ 7438.608668] irq xmitstat 20fe1001 00000080
> [ 7438.608709] irq xmitstat 20000011 00000080
> [ 7438.608724] b43-phy2 debug: Out of order TX status report on DMA ring 1. Expected 256, but got 0
> [ 7438.608739] irq xmitstat 20020011 00000080
> [ 7438.608750] b43-phy2 debug: Out of order TX status report on DMA ring 1. Expected 256, but got 2
> [ 7438.608765] irq xmitstat 20040011 00000080
>
> We write 0xff0 to the TXADDRLO register to see if the DMA engine is
> capable of unaligned operation. If it *is*, then it'll have this problem
> and we have to write the full address to TXINDEX. Comments in brcmsmac
> indicate that the low 13 bits are required.
>
> If we're doing this, we *also* have to write to TXCTL to enable the DMA
> engine *after* setting up the ring address.
>
> Signed-off-by: David Woodhouse<David.Woodhouse at intel.com>
> --
> I've made that change to the initialisation order of TXCTL vs.
> TXADDR{HI,LO} unconditional; is there a reason not to?
>
> diff --git a/drivers/net/wireless/b43/dma.c b/drivers/net/wireless/b43/dma.c
> index 82168f8..92dd6d9 100644
> --- a/drivers/net/wireless/b43/dma.c
> +++ b/drivers/net/wireless/b43/dma.c
> @@ -225,8 +225,10 @@ static void op64_fill_descriptor(struct b43_dmaring *ring,
>
>   static void op64_poke_tx(struct b43_dmaring *ring, int slot)
>   {
> -	b43_dma_write(ring, B43_DMA64_TXINDEX,
> -		      (u32) (slot * sizeof(struct b43_dmadesc64)));
> +	u32 indexval = slot * sizeof(struct b43_dmadesc64);
> +	if (ring->unaligned)
> +		indexval |= (u32)ring->dmabase;
> +	b43_dma_write(ring, B43_DMA64_TXINDEX, indexval);
>   }
>
>   static void op64_tx_suspend(struct b43_dmaring *ring)
> @@ -704,9 +710,14 @@ static int dmacontroller_setup(struct b43_dmaring *ring)
>   			&  B43_DMA64_TXADDREXT_MASK;
>   			if (!parity)
>   				value |= B43_DMA64_TXPARITYDISABLE;
> -			b43_dma_write(ring, B43_DMA64_TXCTL, value);
> +
> +			b43_dma_write(ring, B43_DMA64_TXRINGLO, 0xff0);

Should there be a new symbol rather than this magic number?

> +			if (b43_dma_read(ring, B43_DMA64_TXRINGLO))
> +				ring->unaligned = 1;
> +
>   			b43_dma_write(ring, B43_DMA64_TXRINGLO, addrlo);
>   			b43_dma_write(ring, B43_DMA64_TXRINGHI, addrhi);
> +			b43_dma_write(ring, B43_DMA64_TXCTL, value);
>   		} else {
>   			u32 ringbase = (u32) (ring->dmabase);
>   			addrext = b43_dma_address(&ring->dev->dma, ringbase, B43_DMA_ADDR_EXT);
> diff --git a/drivers/net/wireless/b43/dma.h b/drivers/net/wireless/b43/dma.h
> index 7e20b04f..16dc565 100644
> --- a/drivers/net/wireless/b43/dma.h
> +++ b/drivers/net/wireless/b43/dma.h
> @@ -251,6 +251,8 @@ struct b43_dmaring {
>   	int index;
>   	/* Boolean. Is this a TX ring? */
>   	bool tx;
> +	/* Boolean. Is this ring capable of 16-byte alignment? */
> +	bool unaligned;
>   	/* The type of DMA engine used. */
>   	enum b43_dmatype type;
>   	/* Boolean. Is this ring stopped at ieee80211 level? */
>

Tested on BCM4318 on 32-bit system.

Larry