Re: [PATCH v2 12/14] net: axienet: Upgrade descriptors to hold 64-bit addresses

From: Andre Przywara
Date: Tue Mar 10 2020 - 05:35:37 EST

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On Mon, 9 Mar 2020 12:46:25 -0600
Robert Hancock <hancock@xxxxxxxxxxxxx> wrote:

Hi,

> On 2020-03-09 12:18 p.m., Andre Przywara wrote:
> > Newer revisions of the AXI DMA IP (>= v7.1) support 64-bit addresses,
> > both for the descriptors itself, as well as for the buffers they are
> > pointing to.
> > This is realised by adding "MSB" words for the next and phys pointer
> > right behind the existing address word, now named "LSB". These MSB words
> > live in formerly reserved areas of the descriptor.
> >
> > If the hardware supports it, write both words when setting an address.
> > The buffer address is handled by two wrapper functions, the two
> > occasions where we set the next pointers are open coded.
> >
> > For now this is guarded by a flag which we don't set yet.
> >
> > Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> > ---
> > drivers/net/ethernet/xilinx/xilinx_axienet.h | 9 +-
> > .../net/ethernet/xilinx/xilinx_axienet_main.c | 113 ++++++++++++------
> > 2 files changed, 83 insertions(+), 39 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet.h b/drivers/net/ethernet/xilinx/xilinx_axienet.h
> > index fb7450ca5c53..84c4c3655516 100644
> > --- a/drivers/net/ethernet/xilinx/xilinx_axienet.h
> > +++ b/drivers/net/ethernet/xilinx/xilinx_axienet.h
> > @@ -328,6 +328,7 @@
> > #define XAE_FEATURE_PARTIAL_TX_CSUM (1 << 1)
> > #define XAE_FEATURE_FULL_RX_CSUM (1 << 2)
> > #define XAE_FEATURE_FULL_TX_CSUM (1 << 3)
> > +#define XAE_FEATURE_DMA_64BIT (1 << 4)
> >
> > #define XAE_NO_CSUM_OFFLOAD 0
> >
> > @@ -340,9 +341,9 @@
> > /**
> > * struct axidma_bd - Axi Dma buffer descriptor layout
> > * @next: MM2S/S2MM Next Descriptor Pointer
> > - * @reserved1: Reserved and not used
> > + * @next_msb: MM2S/S2MM Next Descriptor Pointer (high 32 bits)
> > * @phys: MM2S/S2MM Buffer Address
> > - * @reserved2: Reserved and not used
> > + * @phys_msb: MM2S/S2MM Buffer Address (high 32 bits)
> > * @reserved3: Reserved and not used
> > * @reserved4: Reserved and not used
> > * @cntrl: MM2S/S2MM Control value
> > @@ -355,9 +356,9 @@
> > */
> > struct axidma_bd {
> > u32 next; /* Physical address of next buffer descriptor */
> > - u32 reserved1;
> > + u32 next_msb; /* high 32 bits for IP >= v7.1, reserved on older IP */
> > u32 phys;
> > - u32 reserved2;
> > + u32 phys_msb; /* for IP >= v7.1, reserved for older IP */
> > u32 reserved3;
> > u32 reserved4;
> > u32 cntrl;
> > diff --git a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> > index ea44ef4cf288..edee0666d52c 100644
> > --- a/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> > +++ b/drivers/net/ethernet/xilinx/xilinx_axienet_main.c
> > @@ -153,6 +153,25 @@ static void axienet_dma_out_addr(struct axienet_local *lp, off_t reg,
> > axienet_dma_out32(lp, reg, lower_32_bits(addr));
> > }
> >
> > +static void desc_set_phys_addr(struct axienet_local *lp, dma_addr_t addr,
> > + struct axidma_bd *desc)
> > +{
> > + desc->phys = lower_32_bits(addr);
> > + if (lp->features & XAE_FEATURE_DMA_64BIT)
> > + desc->phys_msb = upper_32_bits(addr);
> > +}
> > +
> > +static dma_addr_t desc_get_phys_addr(struct axienet_local *lp,
> > + struct axidma_bd *desc)
> > +{
> > + dma_addr_t ret = desc->phys;
> > +
> > + if (lp->features & XAE_FEATURE_DMA_64BIT)
> > + ret |= (dma_addr_t)desc->phys_msb << 32;
>
> Does this compile/work properly on a 32-bit kernel? If dma_addr_t was a
> 32-bit type, I would expect that left-shifting by 32 bits may not do
> what you want. Not sure if there is an inverse to lower_32_bits and
> upper_32_bits macros?

Ah, good point. I compile-tested on 32-bit, but only with ARM32+LPAE, which makes dma_addr_t 64-bit as well.

I couldn't find any suitable macro in kernel.h, but will try << 16 << 16.

Thanks for spotting this (six hours before the build bot)!

Cheers,
Andre

>
> > +
> > + return ret;
> > +}
> > +
> > /**
> > * axienet_dma_bd_release - Release buffer descriptor rings
> > * @ndev: Pointer to the net_device structure
> > @@ -176,6 +195,8 @@ static void axienet_dma_bd_release(struct net_device *ndev)
> > return;
> >
> > for (i = 0; i < lp->rx_bd_num; i++) {
> > + dma_addr_t phys;
> > +
> > /* A NULL skb means this descriptor has not been initialised
> > * at all.
> > */
> > @@ -188,9 +209,11 @@ static void axienet_dma_bd_release(struct net_device *ndev)
> > * descriptor size, after it had been successfully allocated.
> > * So a non-zero value in there means we need to unmap it.
> > */
> > - if (lp->rx_bd_v[i].cntrl)
> > - dma_unmap_single(ndev->dev.parent, lp->rx_bd_v[i].phys,
> > + if (lp->rx_bd_v[i].cntrl) {
> > + phys = desc_get_phys_addr(lp, &lp->rx_bd_v[i]);
> > + dma_unmap_single(ndev->dev.parent, phys,
> > lp->max_frm_size, DMA_FROM_DEVICE);
> > + }
> > }
> >
> > dma_free_coherent(ndev->dev.parent,
> > @@ -235,29 +258,36 @@ static int axienet_dma_bd_init(struct net_device *ndev)
> > goto out;
> >
> > for (i = 0; i < lp->tx_bd_num; i++) {
> > - lp->tx_bd_v[i].next = lp->tx_bd_p +
> > - sizeof(*lp->tx_bd_v) *
> > - ((i + 1) % lp->tx_bd_num);
> > + dma_addr_t addr = lp->tx_bd_p +
> > + sizeof(*lp->tx_bd_v) *
> > + ((i + 1) % lp->tx_bd_num);
> > +
> > + lp->tx_bd_v[i].next = lower_32_bits(addr);
> > + if (lp->features & XAE_FEATURE_DMA_64BIT)
> > + lp->tx_bd_v[i].next_msb = upper_32_bits(addr);
> > }
> >
> > for (i = 0; i < lp->rx_bd_num; i++) {
> > - lp->rx_bd_v[i].next = lp->rx_bd_p +
> > - sizeof(*lp->rx_bd_v) *
> > - ((i + 1) % lp->rx_bd_num);
> > + dma_addr_t addr;
> > +
> > + addr = lp->rx_bd_p + sizeof(*lp->rx_bd_v) *
> > + ((i + 1) % lp->rx_bd_num);
> > + lp->rx_bd_v[i].next = lower_32_bits(addr);
> > + if (lp->features & XAE_FEATURE_DMA_64BIT)
> > + lp->rx_bd_v[i].next_msb = upper_32_bits(addr);
> >
> > skb = netdev_alloc_skb_ip_align(ndev, lp->max_frm_size);
> > if (!skb)
> > goto out;
> >
> > lp->rx_bd_v[i].skb = skb;
> > - lp->rx_bd_v[i].phys = dma_map_single(ndev->dev.parent,
> > - skb->data,
> > - lp->max_frm_size,
> > - DMA_FROM_DEVICE);
> > - if (dma_mapping_error(ndev->dev.parent, lp->rx_bd_v[i].phys)) {
> > + addr = dma_map_single(ndev->dev.parent, skb->data,
> > + lp->max_frm_size, DMA_FROM_DEVICE);
> > + if (dma_mapping_error(ndev->dev.parent, addr)) {
> > netdev_err(ndev, "DMA mapping error\n");
> > goto out;
> > }
> > + desc_set_phys_addr(lp, addr, &lp->rx_bd_v[i]);
> >
> > lp->rx_bd_v[i].cntrl = lp->max_frm_size;
> > }
> > @@ -573,6 +603,7 @@ static int axienet_free_tx_chain(struct net_device *ndev, u32 first_bd,
> > struct axienet_local *lp = netdev_priv(ndev);
> > int max_bds = (nr_bds != -1) ? nr_bds : lp->tx_bd_num;
> > struct axidma_bd *cur_p;
> > + dma_addr_t phys;
> > unsigned int status;
> > int i;
> >
> > @@ -586,9 +617,10 @@ static int axienet_free_tx_chain(struct net_device *ndev, u32 first_bd,
> > if (nr_bds == -1 && !(status & XAXIDMA_BD_STS_COMPLETE_MASK))
> > break;
> >
> > - dma_unmap_single(ndev->dev.parent, cur_p->phys,
> > - (cur_p->cntrl & XAXIDMA_BD_CTRL_LENGTH_MASK),
> > - DMA_TO_DEVICE);
> > + phys = desc_get_phys_addr(lp, cur_p);
> > + dma_unmap_single(ndev->dev.parent, phys,
> > + (cur_p->cntrl & XAXIDMA_BD_CTRL_LENGTH_MASK),
> > + DMA_TO_DEVICE);
> >
> > if (cur_p->skb && (status & XAXIDMA_BD_STS_COMPLETE_MASK))
> > dev_consume_skb_irq(cur_p->skb);
> > @@ -684,7 +716,7 @@ axienet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
> > u32 csum_start_off;
> > u32 csum_index_off;
> > skb_frag_t *frag;
> > - dma_addr_t tail_p;
> > + dma_addr_t tail_p, phys;
> > struct axienet_local *lp = netdev_priv(ndev);
> > struct axidma_bd *cur_p;
> > u32 orig_tail_ptr = lp->tx_bd_tail;
> > @@ -723,14 +755,15 @@ axienet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
> > cur_p->app0 |= 2; /* Tx Full Checksum Offload Enabled */
> > }
> >
> > - cur_p->phys = dma_map_single(ndev->dev.parent, skb->data,
> > - skb_headlen(skb), DMA_TO_DEVICE);
> > - if (unlikely(dma_mapping_error(ndev->dev.parent, cur_p->phys))) {
> > + phys = dma_map_single(ndev->dev.parent, skb->data,
> > + skb_headlen(skb), DMA_TO_DEVICE);
> > + if (unlikely(dma_mapping_error(ndev->dev.parent, phys))) {
> > if (net_ratelimit())
> > netdev_err(ndev, "TX DMA mapping error\n");
> > ndev->stats.tx_dropped++;
> > return NETDEV_TX_OK;
> > }
> > + desc_set_phys_addr(lp, phys, cur_p);
> > cur_p->cntrl = skb_headlen(skb) | XAXIDMA_BD_CTRL_TXSOF_MASK;
> >
> > for (ii = 0; ii < num_frag; ii++) {
> > @@ -738,11 +771,11 @@ axienet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
> > lp->tx_bd_tail = 0;
> > cur_p = &lp->tx_bd_v[lp->tx_bd_tail];
> > frag = &skb_shinfo(skb)->frags[ii];
> > - cur_p->phys = dma_map_single(ndev->dev.parent,
> > - skb_frag_address(frag),
> > - skb_frag_size(frag),
> > - DMA_TO_DEVICE);
> > - if (unlikely(dma_mapping_error(ndev->dev.parent, cur_p->phys))) {
> > + phys = dma_map_single(ndev->dev.parent,
> > + skb_frag_address(frag),
> > + skb_frag_size(frag),
> > + DMA_TO_DEVICE);
> > + if (unlikely(dma_mapping_error(ndev->dev.parent, phys))) {
> > if (net_ratelimit())
> > netdev_err(ndev, "TX DMA mapping error\n");
> > ndev->stats.tx_dropped++;
> > @@ -752,6 +785,7 @@ axienet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
> >
> > return NETDEV_TX_OK;
> > }
> > + desc_set_phys_addr(lp, phys, cur_p);
> > cur_p->cntrl = skb_frag_size(frag);
> > }
> >
> > @@ -790,10 +824,12 @@ static void axienet_recv(struct net_device *ndev)
> > cur_p = &lp->rx_bd_v[lp->rx_bd_ci];
> >
> > while ((cur_p->status & XAXIDMA_BD_STS_COMPLETE_MASK)) {
> > + dma_addr_t phys;
> > +
> > tail_p = lp->rx_bd_p + sizeof(*lp->rx_bd_v) * lp->rx_bd_ci;
> >
> > - dma_unmap_single(ndev->dev.parent, cur_p->phys,
> > - lp->max_frm_size,
> > + phys = desc_get_phys_addr(lp, cur_p);
> > + dma_unmap_single(ndev->dev.parent, phys, lp->max_frm_size,
> > DMA_FROM_DEVICE);
> >
> > skb = cur_p->skb;
> > @@ -829,15 +865,16 @@ static void axienet_recv(struct net_device *ndev)
> > if (!new_skb)
> > return;
> >
> > - cur_p->phys = dma_map_single(ndev->dev.parent, new_skb->data,
> > - lp->max_frm_size,
> > - DMA_FROM_DEVICE);
> > - if (unlikely(dma_mapping_error(ndev->dev.parent, cur_p->phys))) {
> > + phys = dma_map_single(ndev->dev.parent, new_skb->data,
> > + lp->max_frm_size,
> > + DMA_FROM_DEVICE);
> > + if (unlikely(dma_mapping_error(ndev->dev.parent, phys))) {
> > if (net_ratelimit())
> > netdev_err(ndev, "RX DMA mapping error\n");
> > dev_kfree_skb(new_skb);
> > return;
> > }
> > + desc_set_phys_addr(lp, phys, cur_p);
> >
> > cur_p->cntrl = lp->max_frm_size;
> > cur_p->status = 0;
> > @@ -882,7 +919,8 @@ static irqreturn_t axienet_tx_irq(int irq, void *_ndev)
> > return IRQ_NONE;
> > if (status & XAXIDMA_IRQ_ERROR_MASK) {
> > dev_err(&ndev->dev, "DMA Tx error 0x%x\n", status);
> > - dev_err(&ndev->dev, "Current BD is at: 0x%x\n",
> > + dev_err(&ndev->dev, "Current BD is at: 0x%x%08x\n",
> > + (lp->tx_bd_v[lp->tx_bd_ci]).phys_msb,
> > (lp->tx_bd_v[lp->tx_bd_ci]).phys);
> >
> > cr = axienet_dma_in32(lp, XAXIDMA_TX_CR_OFFSET);
> > @@ -931,7 +969,8 @@ static irqreturn_t axienet_rx_irq(int irq, void *_ndev)
> > return IRQ_NONE;
> > if (status & XAXIDMA_IRQ_ERROR_MASK) {
> > dev_err(&ndev->dev, "DMA Rx error 0x%x\n", status);
> > - dev_err(&ndev->dev, "Current BD is at: 0x%x\n",
> > + dev_err(&ndev->dev, "Current BD is at: 0x%x%08x\n",
> > + (lp->rx_bd_v[lp->rx_bd_ci]).phys_msb,
> > (lp->rx_bd_v[lp->rx_bd_ci]).phys);
> >
> > cr = axienet_dma_in32(lp, XAXIDMA_TX_CR_OFFSET);
> > @@ -1633,14 +1672,18 @@ static void axienet_dma_err_handler(struct work_struct *work)
> >
> > for (i = 0; i < lp->tx_bd_num; i++) {
> > cur_p = &lp->tx_bd_v[i];
> > - if (cur_p->cntrl)
> > - dma_unmap_single(ndev->dev.parent, cur_p->phys,
> > + if (cur_p->cntrl) {
> > + dma_addr_t addr = desc_get_phys_addr(lp, cur_p);
> > +
> > + dma_unmap_single(ndev->dev.parent, addr,
> > (cur_p->cntrl &
> > XAXIDMA_BD_CTRL_LENGTH_MASK),
> > DMA_TO_DEVICE);
> > + }
> > if (cur_p->skb)
> > dev_kfree_skb_irq(cur_p->skb);
> > cur_p->phys = 0;
> > + cur_p->phys_msb = 0;
> > cur_p->cntrl = 0;
> > cur_p->status = 0;
> > cur_p->app0 = 0;
> >
>

Next message: Robin Gong: "RE: [RESEND v6 09/13] dmaengine: imx-sdma: remove ERR009165 on i.mx6ul"
Previous message: Christian Brauner: "[PATCH v19 01/14] fsinfo: Add fsinfo() syscall to query filesystem information"
In reply to: Robert Hancock: "Re: [PATCH v2 12/14] net: axienet: Upgrade descriptors to hold 64-bit addresses"
Next in thread: Andre Przywara: "[PATCH v2 09/14] net: axienet: Drop MDIO interrupt registers from ethtools dump"
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