sfc: Use the correct maximum TX DMA ring size for SFC9100

As part of a workaround for a hardware erratum in the SFC9100 family
(SF bug 35388), the TX_DESC_UPD_DWORD register address is also used
for communicating with the event block, and only descriptor pointer
values < 2048 are valid.

If the TX DMA ring size is increased to 4096 descriptors (which the
firmware still allows) then we may write a descriptor pointer
value >= 2048, which has entirely different and undesirable effects!

Limit the TX DMA ring size correctly when this workaround is in
effect.

Fixes: 8127d661e77f ('sfc: Add support for Solarflare SFC9100 family')
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Shradha Shah <sshah@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/sfc/efx.h b/drivers/net/ethernet/sfc/efx.h
index 6012247..dbd7b78 100644 (file)
--- a/drivers/net/ethernet/sfc/efx.h
+++ b/drivers/net/ethernet/sfc/efx.h
@@ -66,6 +66,9 @@ void efx_schedule_slow_fill(struct efx_rx_queue *rx_queue);
 #define EFX_RXQ_MIN_ENT                128U
 #define EFX_TXQ_MIN_ENT(efx)   (2 * efx_tx_max_skb_descs(efx))
 
+#define EFX_TXQ_MAX_ENT(efx)   (EFX_WORKAROUND_35388(efx) ? \
+                                EFX_MAX_DMAQ_SIZE / 2 : EFX_MAX_DMAQ_SIZE)
+
 /* Filters */
 
 /**

diff --git a/drivers/net/ethernet/sfc/ethtool.c b/drivers/net/ethernet/sfc/ethtool.c
index f181522..2294289 100644 (file)
--- a/drivers/net/ethernet/sfc/ethtool.c
+++ b/drivers/net/ethernet/sfc/ethtool.c
@@ -591,7 +591,7 @@ static void efx_ethtool_get_ringparam(struct net_device *net_dev,
        struct efx_nic *efx = netdev_priv(net_dev);
 
        ring->rx_max_pending = EFX_MAX_DMAQ_SIZE;
-       ring->tx_max_pending = EFX_MAX_DMAQ_SIZE;
+       ring->tx_max_pending = EFX_TXQ_MAX_ENT(efx);
        ring->rx_pending = efx->rxq_entries;
        ring->tx_pending = efx->txq_entries;
 }
@@ -604,7 +604,7 @@ static int efx_ethtool_set_ringparam(struct net_device *net_dev,
 
        if (ring->rx_mini_pending || ring->rx_jumbo_pending ||
            ring->rx_pending > EFX_MAX_DMAQ_SIZE ||
-           ring->tx_pending > EFX_MAX_DMAQ_SIZE)
+           ring->tx_pending > EFX_TXQ_MAX_ENT(efx))
                return -EINVAL;
 
        if (ring->rx_pending < EFX_RXQ_MIN_ENT) {