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SubjectRe: [PATCH 1/4] net: wan: Add support for QMC HDLC
From
On 23/01/2024 16:49, Herve Codina wrote:
> The QMC HDLC driver provides support for HDLC using the QMC (QUICC
> Multichannel Controller) to transfer the HDLC data.
>
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>
> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> Acked-by: Jakub Kicinski <kuba@kernel.org>
> ---
> drivers/net/wan/Kconfig | 12 +
> drivers/net/wan/Makefile | 1 +
> drivers/net/wan/fsl_qmc_hdlc.c | 422 +++++++++++++++++++++++++++++++++
> 3 files changed, 435 insertions(+)
> create mode 100644 drivers/net/wan/fsl_qmc_hdlc.c
>
> diff --git a/drivers/net/wan/Kconfig b/drivers/net/wan/Kconfig
> index 7dda87756d3f..31ab2136cdf1 100644
> --- a/drivers/net/wan/Kconfig
> +++ b/drivers/net/wan/Kconfig
> @@ -197,6 +197,18 @@ config FARSYNC
> To compile this driver as a module, choose M here: the
> module will be called farsync.
>
> +config FSL_QMC_HDLC
> + tristate "Freescale QMC HDLC support"
> + depends on HDLC
> + depends on CPM_QMC
> + help
> + HDLC support using the Freescale QUICC Multichannel Controller (QMC).
> +
> + To compile this driver as a module, choose M here: the
> + module will be called fsl_qmc_hdlc.
> +
> + If unsure, say N.
> +
> config FSL_UCC_HDLC
> tristate "Freescale QUICC Engine HDLC support"
> depends on HDLC
> diff --git a/drivers/net/wan/Makefile b/drivers/net/wan/Makefile
> index 8119b49d1da9..00e9b7ee1e01 100644
> --- a/drivers/net/wan/Makefile
> +++ b/drivers/net/wan/Makefile
> @@ -25,6 +25,7 @@ obj-$(CONFIG_WANXL) += wanxl.o
> obj-$(CONFIG_PCI200SYN) += pci200syn.o
> obj-$(CONFIG_PC300TOO) += pc300too.o
> obj-$(CONFIG_IXP4XX_HSS) += ixp4xx_hss.o
> +obj-$(CONFIG_FSL_QMC_HDLC) += fsl_qmc_hdlc.o
> obj-$(CONFIG_FSL_UCC_HDLC) += fsl_ucc_hdlc.o
> obj-$(CONFIG_SLIC_DS26522) += slic_ds26522.o
>
> diff --git a/drivers/net/wan/fsl_qmc_hdlc.c b/drivers/net/wan/fsl_qmc_hdlc.c
> new file mode 100644
> index 000000000000..31b637ec8390
> --- /dev/null
> +++ b/drivers/net/wan/fsl_qmc_hdlc.c
> @@ -0,0 +1,422 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Freescale QMC HDLC Device Driver
> + *
> + * Copyright 2023 CS GROUP France
> + *
> + * Author: Herve Codina <herve.codina@bootlin.com>
> + */
> +
> +#include <linux/dma-mapping.h>
> +#include <linux/hdlc.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <soc/fsl/qe/qmc.h>
> +
> +struct qmc_hdlc_desc {
> + struct net_device *netdev;
> + struct sk_buff *skb; /* NULL if the descriptor is not in use */
> + dma_addr_t dma_addr;
> + size_t dma_size;
> +};
> +
> +struct qmc_hdlc {
> + struct device *dev;
> + struct qmc_chan *qmc_chan;
> + struct net_device *netdev;
> + bool is_crc32;
> + spinlock_t tx_lock; /* Protect tx descriptors */
> + struct qmc_hdlc_desc tx_descs[8];
> + unsigned int tx_out;
> + struct qmc_hdlc_desc rx_descs[4];
> +};
> +
> +static inline struct qmc_hdlc *netdev_to_qmc_hdlc(struct net_device *netdev)
> +{
> + return dev_to_hdlc(netdev)->priv;
> +}
> +
> +static int qmc_hdlc_recv_queue(struct qmc_hdlc *qmc_hdlc, struct qmc_hdlc_desc *desc, size_t size);
> +
> +#define QMC_HDLC_RX_ERROR_FLAGS (QMC_RX_FLAG_HDLC_OVF | \
> + QMC_RX_FLAG_HDLC_UNA | \
> + QMC_RX_FLAG_HDLC_ABORT | \
> + QMC_RX_FLAG_HDLC_CRC)
> +
> +static void qmc_hcld_recv_complete(void *context, size_t length, unsigned int flags)
> +{
> + struct qmc_hdlc_desc *desc = context;
> + struct net_device *netdev = desc->netdev;
> + struct qmc_hdlc *qmc_hdlc = netdev_to_qmc_hdlc(desc->netdev);

a line above desc->netdev was stored in netdev. better to reuse it and
make declaration part consistent with qmc_hcld_xmit_complete

> + int ret;
> +
> + dma_unmap_single(qmc_hdlc->dev, desc->dma_addr, desc->dma_size, DMA_FROM_DEVICE);
> +
> + if (flags & QMC_HDLC_RX_ERROR_FLAGS) {
> + netdev->stats.rx_errors++;
> + if (flags & QMC_RX_FLAG_HDLC_OVF) /* Data overflow */
> + netdev->stats.rx_over_errors++;
> + if (flags & QMC_RX_FLAG_HDLC_UNA) /* bits received not multiple of 8 */
> + netdev->stats.rx_frame_errors++;
> + if (flags & QMC_RX_FLAG_HDLC_ABORT) /* Received an abort sequence */
> + netdev->stats.rx_frame_errors++;
> + if (flags & QMC_RX_FLAG_HDLC_CRC) /* CRC error */
> + netdev->stats.rx_crc_errors++;
> + kfree_skb(desc->skb);
> + } else {
> + netdev->stats.rx_packets++;
> + netdev->stats.rx_bytes += length;
> +
> + skb_put(desc->skb, length);
> + desc->skb->protocol = hdlc_type_trans(desc->skb, netdev);
> + netif_rx(desc->skb);
> + }
> +
> + /* Re-queue a transfer using the same descriptor */
> + ret = qmc_hdlc_recv_queue(qmc_hdlc, desc, desc->dma_size);
> + if (ret) {
> + dev_err(qmc_hdlc->dev, "queue recv desc failed (%d)\n", ret);
> + netdev->stats.rx_errors++;
> + }
> +}
> +
> +static int qmc_hdlc_recv_queue(struct qmc_hdlc *qmc_hdlc, struct qmc_hdlc_desc *desc, size_t size)
> +{
> + int ret;
> +
> + desc->skb = dev_alloc_skb(size);
> + if (!desc->skb)
> + return -ENOMEM;
> +
> + desc->dma_size = size;
> + desc->dma_addr = dma_map_single(qmc_hdlc->dev, desc->skb->data,
> + desc->dma_size, DMA_FROM_DEVICE);
> + ret = dma_mapping_error(qmc_hdlc->dev, desc->dma_addr);
> + if (ret)
> + goto free_skb;
> +
> + ret = qmc_chan_read_submit(qmc_hdlc->qmc_chan, desc->dma_addr, desc->dma_size,
> + qmc_hcld_recv_complete, desc);
> + if (ret)
> + goto dma_unmap;
> +
> + return 0;
> +
> +dma_unmap:
> + dma_unmap_single(qmc_hdlc->dev, desc->dma_addr, desc->dma_size, DMA_FROM_DEVICE);
> +free_skb:
> + kfree_skb(desc->skb);
> + desc->skb = NULL;
> + return ret;
> +}
> +
> +static void qmc_hdlc_xmit_complete(void *context)
> +{
> + struct qmc_hdlc_desc *desc = context;
> + struct net_device *netdev = desc->netdev;
> + struct qmc_hdlc *qmc_hdlc = netdev_to_qmc_hdlc(netdev);
> + struct sk_buff *skb;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&qmc_hdlc->tx_lock, flags);
> + dma_unmap_single(qmc_hdlc->dev, desc->dma_addr, desc->dma_size, DMA_TO_DEVICE);
> + skb = desc->skb;
> + desc->skb = NULL; /* Release the descriptor */
> + if (netif_queue_stopped(netdev))
> + netif_wake_queue(netdev);
> + spin_unlock_irqrestore(&qmc_hdlc->tx_lock, flags);
> +
> + netdev->stats.tx_packets++;
> + netdev->stats.tx_bytes += skb->len;
> +
> + dev_consume_skb_any(skb);
> +}
> +
> +static int qmc_hdlc_xmit_queue(struct qmc_hdlc *qmc_hdlc, struct qmc_hdlc_desc *desc)
> +{
> + int ret;
> +
> + desc->dma_addr = dma_map_single(qmc_hdlc->dev, desc->skb->data,
> + desc->dma_size, DMA_TO_DEVICE);
> + ret = dma_mapping_error(qmc_hdlc->dev, desc->dma_addr);
> + if (ret) {
> + dev_err(qmc_hdlc->dev, "failed to map skb\n");
> + return ret;
> + }
> +
> + ret = qmc_chan_write_submit(qmc_hdlc->qmc_chan, desc->dma_addr, desc->dma_size,
> + qmc_hdlc_xmit_complete, desc);
> + if (ret) {
> + dev_err(qmc_hdlc->dev, "qmc chan write returns %d\n", ret);
> + dma_unmap_single(qmc_hdlc->dev, desc->dma_addr, desc->dma_size, DMA_TO_DEVICE);
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +static netdev_tx_t qmc_hdlc_xmit(struct sk_buff *skb, struct net_device *netdev)
> +{
> + struct qmc_hdlc *qmc_hdlc = netdev_to_qmc_hdlc(netdev);
> + struct qmc_hdlc_desc *desc;
> + unsigned long flags;
> + int ret;
> +
> + spin_lock_irqsave(&qmc_hdlc->tx_lock, flags);
> + desc = &qmc_hdlc->tx_descs[qmc_hdlc->tx_out];
> + if (desc->skb) {
> + /* Should never happen.
> + * Previous xmit should have already stopped the queue.
> + */

according to the comment it's better to make if(unlikely(desc->skb)) or
even WARN_ONCE()

> + netif_stop_queue(netdev);
> + spin_unlock_irqrestore(&qmc_hdlc->tx_lock, flags);
> + return NETDEV_TX_BUSY;
> + }
> + spin_unlock_irqrestore(&qmc_hdlc->tx_lock, flags);

[...]

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