linux/drivers/net/ethernet/stmicro/stmmac/chain_mode.c

// SPDX-License-Identifier: GPL-2.0-only
/*******************************************************************************
  Specialised functions for managing Chained mode

  Copyright(C) 2011  STMicroelectronics Ltd

  It defines all the functions used to handle the normal/enhanced
  descriptors in case of the DMA is configured to work in chained or
  in ring mode.


  Author: Giuseppe Cavallaro <peppe.cavallaro@st.com>
*******************************************************************************/

#include "stmmac.h"

static int jumbo_frm(struct stmmac_tx_queue *tx_q, struct sk_buff *skb,
		     int csum)
{
	unsigned int nopaged_len = skb_headlen(skb);
	struct stmmac_priv *priv = tx_q->priv_data;
	unsigned int entry = tx_q->cur_tx;
	unsigned int bmax, buf_len, des2;
	unsigned int i = 1, len;
	struct dma_desc *desc;

	desc = tx_q->dma_tx + entry;

	if (priv->plat->enh_desc)
		bmax = BUF_SIZE_8KiB;
	else
		bmax = BUF_SIZE_2KiB;

	buf_len = min_t(unsigned int, nopaged_len, bmax);
	len = nopaged_len - buf_len;

	des2 = dma_map_single(priv->device, skb->data,
			      buf_len, DMA_TO_DEVICE);
	desc->des2 = cpu_to_le32(des2);
	if (dma_mapping_error(priv->device, des2))
		return -1;
	tx_q->tx_skbuff_dma[entry].buf = des2;
	tx_q->tx_skbuff_dma[entry].len = buf_len;
	/* do not close the descriptor and do not set own bit */
	stmmac_prepare_tx_desc(priv, desc, 1, buf_len, csum, STMMAC_CHAIN_MODE,
			0, false, skb->len);

	while (len != 0) {
		tx_q->tx_skbuff[entry] = NULL;
		entry = STMMAC_NEXT_ENTRY(entry, priv->dma_conf.dma_tx_size);
		desc = tx_q->dma_tx + entry;

		if (len > bmax) {
			des2 = dma_map_single(priv->device,
					      (skb->data + bmax * i),
					      bmax, DMA_TO_DEVICE);
			desc->des2 = cpu_to_le32(des2);
			if (dma_mapping_error(priv->device, des2))
				return -1;
			tx_q->tx_skbuff_dma[entry].buf = des2;
			tx_q->tx_skbuff_dma[entry].len = bmax;
			stmmac_prepare_tx_desc(priv, desc, 0, bmax, csum,
					STMMAC_CHAIN_MODE, 1, false, skb->len);
			len -= bmax;
			i++;
		} else {
			des2 = dma_map_single(priv->device,
					      (skb->data + bmax * i), len,
					      DMA_TO_DEVICE);
			desc->des2 = cpu_to_le32(des2);
			if (dma_mapping_error(priv->device, des2))
				return -1;
			tx_q->tx_skbuff_dma[entry].buf = des2;
			tx_q->tx_skbuff_dma[entry].len = len;
			/* last descriptor can be set now */
			stmmac_prepare_tx_desc(priv, desc, 0, len, csum,
					STMMAC_CHAIN_MODE, 1, true, skb->len);
			len = 0;
		}
	}

	tx_q->cur_tx = entry;

	return entry;
}

static bool is_jumbo_frm(unsigned int len, bool enh_desc)
{
	bool ret = false;

	if ((enh_desc && (len > BUF_SIZE_8KiB)) ||
	    (!enh_desc && (len > BUF_SIZE_2KiB)))
		ret = true;

	return ret;
}

static void init_dma_chain(void *des, dma_addr_t phy_addr,
				  unsigned int size, unsigned int extend_desc)
{
	/*
	 * In chained mode the des3 points to the next element in the ring.
	 * The latest element has to point to the head.
	 */
	int i;
	dma_addr_t dma_phy = phy_addr;

	if (extend_desc) {
		struct dma_extended_desc *p = (struct dma_extended_desc *)des;
		for (i = 0; i < (size - 1); i++) {
			dma_phy += sizeof(struct dma_extended_desc);
			p->basic.des3 = cpu_to_le32((unsigned int)dma_phy);
			p++;
		}
		p->basic.des3 = cpu_to_le32((unsigned int)phy_addr);

	} else {
		struct dma_desc *p = (struct dma_desc *)des;
		for (i = 0; i < (size - 1); i++) {
			dma_phy += sizeof(struct dma_desc);
			p->des3 = cpu_to_le32((unsigned int)dma_phy);
			p++;
		}
		p->des3 = cpu_to_le32((unsigned int)phy_addr);
	}
}

static void refill_desc3(struct stmmac_rx_queue *rx_q, struct dma_desc *p)
{
	struct stmmac_priv *priv = rx_q->priv_data;

	if (priv->hwts_rx_en && !priv->extend_desc)
		/* NOTE: Device will overwrite des3 with timestamp value if
		 * 1588-2002 time stamping is enabled, hence reinitialize it
		 * to keep explicit chaining in the descriptor.
		 */
		p->des3 = cpu_to_le32((unsigned int)(rx_q->dma_rx_phy +
				      (((rx_q->dirty_rx) + 1) %
				       priv->dma_conf.dma_rx_size) *
				      sizeof(struct dma_desc)));
}

static void clean_desc3(struct stmmac_tx_queue *tx_q, struct dma_desc *p)
{
	struct stmmac_priv *priv = tx_q->priv_data;
	unsigned int entry = tx_q->dirty_tx;

	if (tx_q->tx_skbuff_dma[entry].last_segment && !priv->extend_desc &&
	    priv->hwts_tx_en)
		/* NOTE: Device will overwrite des3 with timestamp value if
		 * 1588-2002 time stamping is enabled, hence reinitialize it
		 * to keep explicit chaining in the descriptor.
		 */
		p->des3 = cpu_to_le32((unsigned int)((tx_q->dma_tx_phy +
				      ((tx_q->dirty_tx + 1) %
				       priv->dma_conf.dma_tx_size))
				      * sizeof(struct dma_desc)));
}

const struct stmmac_mode_ops chain_mode_ops = {
	.init = init_dma_chain,
	.is_jumbo_frm = is_jumbo_frm,
	.jumbo_frm = jumbo_frm,
	.refill_desc3 = refill_desc3,
	.clean_desc3 = clean_desc3,
};