Re: [PATCH net-next 7/8] net: eth: altera: tse: add msgdma prefetcher

From: Dalon Westergreen <redacted>

Add support for the mSGDMA prefetcher.  The prefetcher adds support
for a linked list of descriptors in system memory.  The prefetcher
feeds these to the mSGDMA dispatcher.

The prefetcher is configured to poll for the next descriptor in the
list to be owned by hardware, then pass the descriptor to the
dispatcher.  It will then poll the next descriptor until it is
owned by hardware.

The dispatcher responses are written back to the appropriate
descriptor, and the owned by hardware bit is cleared.

The driver sets up a linked list twice the tx and rx ring sizes,
with the last descriptor pointing back to the first.  This ensures
that the ring of descriptors will always have inactive descriptors
preventing the prefetcher from looping over and reusing descriptors
inappropriately.  The prefetcher will continuously loop over these
descriptors.  The driver modifies descriptors as required to update
the skb address and length as well as the owned by hardware bit.

In addition to the above, the mSGDMA prefetcher can be used to
handle rx and tx timestamps coming from the ethernet ip.  These
can be included in the prefetcher response in the descriptor.

Signed-off-by: Dalon Westergreen <redacted>
---
  drivers/net/ethernet/altera/Makefile          |   2 +-
  .../altera/altera_msgdma_prefetcher.c         | 433 ++++++++++++++++++
  .../altera/altera_msgdma_prefetcher.h         |  30 ++
  .../altera/altera_msgdmahw_prefetcher.h       |  87 ++++
  drivers/net/ethernet/altera/altera_tse.h      |  14 +
  drivers/net/ethernet/altera/altera_tse_main.c |  51 +++
  6 files changed, 616 insertions(+), 1 deletion(-)
  create mode 100644 drivers/net/ethernet/altera/altera_msgdma_prefetcher.c
  create mode 100644 drivers/net/ethernet/altera/altera_msgdma_prefetcher.h
  create mode 100644 drivers/net/ethernet/altera/altera_msgdmahw_prefetcher.h

diff --git a/drivers/net/ethernet/altera/Makefile b/drivers/net/ethernet/altera/Makefile
index ad80be42fa26..73b32876f126 100644
--- a/drivers/net/ethernet/altera/Makefile
+++ b/drivers/net/ethernet/altera/Makefile

@@ -5,4 +5,4 @@
  obj-$(CONFIG_ALTERA_TSE) += altera_tse.o
  altera_tse-objs := altera_tse_main.o altera_tse_ethtool.o \
  		   altera_msgdma.o altera_sgdma.o altera_utils.o \
-		   altera_ptp.o
+		   altera_ptp.o altera_msgdma_prefetcher.o

diff --git a/drivers/net/ethernet/altera/altera_msgdma_prefetcher.c b/drivers/net/ethernet/altera/altera_msgdma_prefetcher.c
new file mode 100644
index 000000000000..55b475e9e15b
--- /dev/null
+++ b/drivers/net/ethernet/altera/altera_msgdma_prefetcher.c

@@ -0,0 +1,433 @@
+// SPDX-License-Identifier: GPL-2.0
+/* MSGDMA Prefetcher driver for Altera ethernet devices
+ *
+ * Copyright (C) 2018 Intel Corporation. All rights reserved.
+ * Author(s):
+ *   Dalon Westergreen <dalon.westergreen@intel.com>
+ */
+
+#include <linux/list.h>
+#include <linux/netdevice.h>
+#include <linux/net_tstamp.h>
+#include "altera_utils.h"
+#include "altera_tse.h"
+#include "altera_msgdma.h"
+#include "altera_msgdmahw.h"
+#include "altera_msgdma_prefetcher.h"
+#include "altera_msgdmahw_prefetcher.h"

+
+int msgdma_pref_initialize(struct altera_tse_private *priv)
+{
+	int i;
+	struct msgdma_pref_extended_desc *rx_descs;
+	struct msgdma_pref_extended_desc *tx_descs;
+	dma_addr_t rx_descsphys;
+	dma_addr_t tx_descsphys;
+	u32 rx_ring_size;
+	u32 tx_ring_size;
+
+	priv->pref_rxdescphys = (dma_addr_t)0;
+	priv->pref_txdescphys = (dma_addr_t)0;
+
+	/* we need to allocate more pref descriptors than ringsize, for now
+	 * just double ringsize
+	 */
+	rx_ring_size = priv->rx_ring_size * 2;
+	tx_ring_size = priv->tx_ring_size * 2;
+
+	/* The prefetcher requires the descriptors to be aligned to the
+	 * descriptor read/write master's data width which worst case is
+	 * 512 bits.  Currently we DO NOT CHECK THIS and only support 32-bit
+	 * prefetcher masters.
+	 */
+
+	/* allocate memory for rx descriptors */
+	priv->pref_rxdesc =
+		dma_zalloc_coherent(priv->device,
+				    sizeof(struct msgdma_pref_extended_desc)
+				    * rx_ring_size,
+				    &priv->pref_rxdescphys, GFP_KERNEL);
+
+	if (!priv->pref_rxdesc)
+		goto err_rx;
+
+	/* allocate memory for tx descriptors */
+	priv->pref_txdesc =
+		dma_zalloc_coherent(priv->device,
+				    sizeof(struct msgdma_pref_extended_desc)
+				    * tx_ring_size,
+				    &priv->pref_txdescphys, GFP_KERNEL);
+
+	if (!priv->pref_txdesc)
+		goto err_tx;
+
+	/* setup base descriptor ring for tx & rx */
+	rx_descs = (struct msgdma_pref_extended_desc *)priv->pref_rxdesc;
+	tx_descs = (struct msgdma_pref_extended_desc *)priv->pref_txdesc;
+	tx_descsphys = priv->pref_txdescphys;
+	rx_descsphys = priv->pref_rxdescphys;
+
+	/* setup RX descriptors */
+	priv->pref_rx_prod = 0;
+	for (i = 0; i < rx_ring_size; i++) {
+		rx_descsphys = priv->pref_rxdescphys +
+			(((i + 1) % rx_ring_size) *
+			sizeof(struct msgdma_pref_extended_desc));
+		rx_descs[i].next_desc_lo = lower_32_bits(rx_descsphys);
+		rx_descs[i].next_desc_hi = upper_32_bits(rx_descsphys);
+		rx_descs[i].stride = MSGDMA_DESC_RX_STRIDE;
+		/* burst set to 0 so it defaults to max configured */
+		/* set seq number to desc number */
+		rx_descs[i].burst_seq_num = i;
+	}
+
+	/* setup TX descriptors */
+	for (i = 0; i < tx_ring_size; i++) {
+		tx_descsphys = priv->pref_txdescphys +
+			(((i + 1) % tx_ring_size) *
+			sizeof(struct msgdma_pref_extended_desc));
+		tx_descs[i].next_desc_lo = lower_32_bits(tx_descsphys);
+		tx_descs[i].next_desc_hi = upper_32_bits(tx_descsphys);
+		tx_descs[i].stride = MSGDMA_DESC_TX_STRIDE;
+		/* burst set to 0 so it defaults to max configured */
+		/* set seq number to desc number */
+		tx_descs[i].burst_seq_num = i;
+	}
+
+	if (netif_msg_ifup(priv))
+		netdev_info(priv->dev, "%s: RX Desc mem at 0x%x\n", __func__,
+			    priv->pref_rxdescphys);
+
+	if (netif_msg_ifup(priv))
+		netdev_info(priv->dev, "%s: TX Desc mem at 0x%x\n", __func__,
+			    priv->pref_txdescphys);
+
+	return 0;
+
+err_tx:
+	dma_free_coherent(priv->device,
+			  sizeof(struct msgdma_pref_extended_desc)
+			  * rx_ring_size,
+			  priv->pref_rxdesc, priv->pref_rxdescphys);
+err_rx:
+	return -ENOMEM;
+}
+
+void msgdma_pref_uninitialize(struct altera_tse_private *priv)
+{
+	if (priv->pref_rxdesc)
+		dma_free_coherent(priv->device,
+				  sizeof(struct msgdma_pref_extended_desc)
+				  * priv->rx_ring_size * 2,
+				  priv->pref_rxdesc, priv->pref_rxdescphys);
+
+	if (priv->pref_txdesc)
+		dma_free_coherent(priv->device,
+				  sizeof(struct msgdma_pref_extended_desc)
+				  * priv->rx_ring_size * 2,
+				  priv->pref_txdesc, priv->pref_txdescphys);

+}
+
+void msgdma_pref_enable_txirq(struct altera_tse_private *priv)
+{
+	tse_set_bit(priv->tx_pref_csr, msgdma_pref_csroffs(control),
+		    MSGDMA_PREF_CTL_GLOBAL_INTR);
+}
+

+
+void msgdma_pref_reset(struct altera_tse_private *priv)
+{
+	int counter;
+
+	/* turn off polling */
+	tse_clear_bit(priv->rx_pref_csr, msgdma_pref_csroffs(control),
+		      MSGDMA_PREF_CTL_DESC_POLL_EN);
+	tse_clear_bit(priv->tx_pref_csr, msgdma_pref_csroffs(control),
+		      MSGDMA_PREF_CTL_DESC_POLL_EN);
+
+	/* Reset the RX Prefetcher */
+	csrwr32(MSGDMA_PREF_STAT_IRQ, priv->rx_pref_csr,
+		msgdma_pref_csroffs(status));
+	csrwr32(MSGDMA_PREF_CTL_RESET, priv->rx_pref_csr,
+		msgdma_pref_csroffs(control));
+
+	counter = 0;
+	while (counter++ < ALTERA_TSE_SW_RESET_WATCHDOG_CNTR) {
+		if (tse_bit_is_clear(priv->rx_pref_csr,
+				     msgdma_pref_csroffs(control),
+				     MSGDMA_PREF_CTL_RESET))
+			break;
+		udelay(1);
+	}
+
+	if (counter >= ALTERA_TSE_SW_RESET_WATCHDOG_CNTR)
+		netif_warn(priv, drv, priv->dev,
+			   "TSE Rx Prefetcher reset bit never cleared!\n");
+

+	/* clear all status bits */
+	csrwr32(MSGDMA_PREF_STAT_IRQ, priv->tx_pref_csr,
+		msgdma_pref_csroffs(status));
+

+	/* Reset the TX Prefetcher */
+	csrwr32(MSGDMA_PREF_STAT_IRQ, priv->tx_pref_csr,
+		msgdma_pref_csroffs(status));
+	csrwr32(MSGDMA_PREF_CTL_RESET, priv->tx_pref_csr,
+		msgdma_pref_csroffs(control));
+
+	counter = 0;
+	while (counter++ < ALTERA_TSE_SW_RESET_WATCHDOG_CNTR) {
+		if (tse_bit_is_clear(priv->tx_pref_csr,
+				     msgdma_pref_csroffs(control),
+				     MSGDMA_PREF_CTL_RESET))
+			break;
+		udelay(1);
+	}
+
+	if (counter >= ALTERA_TSE_SW_RESET_WATCHDOG_CNTR)
+		netif_warn(priv, drv, priv->dev,
+			   "TSE Tx Prefetcher reset bit never cleared!\n");
+

+	/* clear all status bits */
+	csrwr32(MSGDMA_PREF_STAT_IRQ, priv->tx_pref_csr,
+		msgdma_pref_csroffs(status));
+
+	/* Reset mSGDMA dispatchers*/
+	msgdma_reset(priv);
+}
+

+
+/* Add MSGDMA Prefetcher Descriptor to descriptor list
+ *   -> This should never be called when a descriptor isn't available
+ */
+void msgdma_pref_add_rx_desc(struct altera_tse_private *priv,
+			     struct tse_buffer *rxbuffer)
+{
+	struct msgdma_pref_extended_desc *rx_descs = priv->pref_rxdesc;
+	u32 desc_entry = priv->pref_rx_prod % (priv->rx_ring_size * 2);
+
+	/* write descriptor entries */
+	rx_descs[desc_entry].len = priv->rx_dma_buf_sz;
+	rx_descs[desc_entry].write_addr_lo = lower_32_bits(rxbuffer->dma_addr);
+	rx_descs[desc_entry].write_addr_hi = upper_32_bits(rxbuffer->dma_addr);
+
+	/* set the control bits and set owned by hw */
+	rx_descs[desc_entry].desc_control = (MSGDMA_DESC_CTL_END_ON_EOP
+			| MSGDMA_DESC_CTL_END_ON_LEN
+			| MSGDMA_DESC_CTL_TR_COMP_IRQ
+			| MSGDMA_DESC_CTL_EARLY_IRQ
+			| MSGDMA_DESC_CTL_TR_ERR_IRQ
+			| MSGDMA_DESC_CTL_GO
+			| MSGDMA_PREF_DESC_CTL_OWNED_BY_HW);
+
+	/* we need to keep a separate one for rx as RX_DESCRIPTORS are
+	 * pre-configured at startup
+	 */
+	priv->pref_rx_prod++;

+
+	if (netif_msg_rx_status(priv)) {
+		netdev_info(priv->dev, "%s: desc: %d buf: %d control 0x%x\n",
+			    __func__, desc_entry,
+			    priv->rx_prod % priv->rx_ring_size,
+			    priv->pref_rxdesc[desc_entry].desc_control);
+	}
+}
+