sfc: Allocate and link PIO buffers; map them with write-combining

Try to allocate a segment of PIO buffer to each TX channel.  If
allocation fails, log an error but continue.

PIO buffers must be mapped separately from the NIC registers, with
write-combining enabled.  Where the host page size is 4K, we could
potentially map each VI's registers and PIO buffer separately.
However, this would add significant complexity, and we also need to
support architectures such as POWER which have a greater page size.
So make a single contiguous write-combining mapping after the
uncacheable mapping, aligned to the host page size, and link PIO
buffers there.  Where necessary, allocate additional VIs within
the write-combining mapping purely for access to PIO buffers.

Link all TX buffers to TX queues and the additional VIs in
efx_ef10_dimension_resources() and in efx_ef10_init_nic() after
an MC reboot.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index b172ed133055..6febecc46e86 100644
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -182,6 +182,9 @@ struct efx_tx_buffer {
  * @tsoh_page: Array of pages of TSO header buffers
  * @txd: The hardware descriptor ring
  * @ptr_mask: The size of the ring minus 1.
+ * @piobuf: PIO buffer region for this TX queue (shared with its partner).
+ *	Size of the region is efx_piobuf_size.
+ * @piobuf_offset: Buffer offset to be specified in PIO descriptors
  * @initialised: Has hardware queue been initialised?
  * @read_count: Current read pointer.
  *	This is the number of buffers that have been removed from both rings.
@@ -223,6 +226,8 @@ struct efx_tx_queue {
 	struct efx_buffer *tsoh_page;
 	struct efx_special_buffer txd;
 	unsigned int ptr_mask;
+	void __iomem *piobuf;
+	unsigned int piobuf_offset;
 	bool initialised;
 
 	/* Members used mainly on the completion path */