IB/ipath: Enable 4KB MTU

Enable use of 4KB MTU.  Since the driver uses more pinned memory for
receive buffers when the 4KB MTU is enabled, whether or not the fabric
supports that MTU, add a "mtu4096" module parameter that can be used to
limit the MTU to 2KB when it is known that 4KB MTUs can't be used
anyway.

Signed-off-by: Dave Olson <dave.olson@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/drivers/infiniband/hw/ipath/ipath_file_ops.c b/drivers/infiniband/hw/ipath/ipath_file_ops.c
index 219b62d32eed..cddf29b9554e 100644
--- a/drivers/infiniband/hw/ipath/ipath_file_ops.c
+++ b/drivers/infiniband/hw/ipath/ipath_file_ops.c
@@ -219,7 +219,12 @@ static int ipath_get_base_info(struct file *fp,
         kinfo->spi_pioalign = dd->ipath_palign;
 
         kinfo->spi_qpair = IPATH_KD_QP;
-        kinfo->spi_piosize = dd->ipath_ibmaxlen;
+        /*
+         * user mode PIO buffers are always 2KB, even when 4KB can
+         * be received, and sent via the kernel; this is ibmaxlen
+         * for 2K MTU.
+         */
+        kinfo->spi_piosize = dd->ipath_piosize2k - 2 * sizeof(u32);
         kinfo->spi_mtu = dd->ipath_ibmaxlen;    /* maxlen, not ibmtu */
         kinfo->spi_port = pd->port_port;
         kinfo->spi_subport = subport_fp(fp);