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Re: [Qemu-devel] [PATCH v2 4/7] hw/net/stellaris_enet: Correctly impleme
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH v2 4/7] hw/net/stellaris_enet: Correctly implement the TR and THR registers |
Date: |
Wed, 2 Apr 2014 16:33:20 +0100 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
* Peter Maydell (address@hidden) wrote:
> Packet transmission for the stellaris ethernet controller can be triggered
> in one of two ways:
> * by setting a threshold value in the THR register; when the FIFO
> fill level reaches the threshold, the h/w starts transmitting.
> Software has to finish filling the FIFO before the transmit
> process completes to avoid a (silent) underrun
> * by software writing to the TR register to explicitly trigger
> transmission
>
> Since QEMU transmits packets instantaneously (from the guest's
> point of view), implement "transmit based on threshold" with
> our existing mechanism of "transmit as soon as we have the whole
> packet", with the additional wrinkle that we don't transmit if
> the packet size is below the specified threshold, and implement
> "transmit by specific request" properly.
>
> Signed-off-by: Peter Maydell <address@hidden>
Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> ---
> hw/net/stellaris_enet.c | 17 +++++++++++++++--
> 1 file changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/hw/net/stellaris_enet.c b/hw/net/stellaris_enet.c
> index 47787fd..db6e43e 100644
> --- a/hw/net/stellaris_enet.c
> +++ b/hw/net/stellaris_enet.c
> @@ -109,6 +109,15 @@ static inline bool
> stellaris_txpacket_complete(stellaris_enet_state *s)
> return s->tx_fifo_len >= framelen;
> }
>
> +/* Return true if the TX FIFO threshold is enabled and the FIFO
> + * has filled enough to reach it.
> + */
> +static inline bool stellaris_tx_thr_reached(stellaris_enet_state *s)
> +{
> + return (s->thr < 0x3f &&
> + (s->tx_fifo_len >= 4 * (s->thr * 8 + 1)));
> +}
> +
> /* Send the packet currently in the TX FIFO */
> static void stellaris_enet_send(stellaris_enet_state *s)
> {
> @@ -309,7 +318,7 @@ static void stellaris_enet_write(void *opaque, hwaddr
> offset,
> s->tx_fifo[s->tx_fifo_len++] = value >> 24;
> }
>
> - if (stellaris_txpacket_complete(s)) {
> + if (stellaris_tx_thr_reached(s) && stellaris_txpacket_complete(s)) {
> stellaris_enet_send(s);
> }
> break;
> @@ -338,9 +347,13 @@ static void stellaris_enet_write(void *opaque, hwaddr
> offset,
> case 0x2c: /* MTXD */
> s->mtxd = value & 0xff;
> break;
> + case 0x38: /* TR */
> + if (value & 1) {
> + stellaris_enet_send(s);
> + }
> + break;
> case 0x30: /* MRXD */
> case 0x34: /* NP */
> - case 0x38: /* TR */
> /* Ignored. */
> case 0x3c: /* Undocuented: Timestamp? */
> /* Ignored. */
> --
> 1.9.0
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [Qemu-devel] [PATCH v2 0/7] stellaris_enet: overhaul tx/rx, convert to vmstate, Peter Maydell, 2014/04/01
- [Qemu-devel] [PATCH v2 7/7] hw/net/stellaris_enet: Convert to vmstate, Peter Maydell, 2014/04/01
- [Qemu-devel] [PATCH v2 4/7] hw/net/stellaris_enet: Correctly implement the TR and THR registers, Peter Maydell, 2014/04/01
- Re: [Qemu-devel] [PATCH v2 4/7] hw/net/stellaris_enet: Correctly implement the TR and THR registers,
Dr. David Alan Gilbert <=
- [Qemu-devel] [PATCH v2 3/7] hw/net/stellaris_enet: Rewrite tx fifo handling code, Peter Maydell, 2014/04/01
- [Qemu-devel] [PATCH v2 6/7] hw/net/stellaris_enet: Get rid of rx_fifo pointer, Peter Maydell, 2014/04/01
- [Qemu-devel] [PATCH v2 1/7] hw/net/stellaris_enet: Restructure tx_fifo code to avoid buffer overrun, Peter Maydell, 2014/04/01
- [Qemu-devel] [PATCH v2 5/7] hw/net/stellaris_enet: Fix debug format strings, Peter Maydell, 2014/04/01
- [Qemu-devel] [PATCH v2 2/7] hw/net/stellaris_enet: Correct handling of packet padding, Peter Maydell, 2014/04/01
- Re: [Qemu-devel] [PATCH v2 0/7] stellaris_enet: overhaul tx/rx, convert to vmstate, Michael S. Tsirkin, 2014/04/28