[PATCH] rtw88: pci: Use general byte arrays as the elements of RX ring

From: Jian-Hong Pan
Date: Thu Jul 25 2019 - 14:04:13 EST


Each skb as the element in RX ring was expected with sized buffer 8216
(RTK_PCI_RX_BUF_SIZE) bytes. However, the skb buffer's true size is
16640 bytes for alignment after allocated, x86_64 for example. And, the
difference will be enlarged 512 times (RTK_MAX_RX_DESC_NUM).
To prevent that much wasted memory, this patch follows David's
suggestion [1] and uses general buffer arrays, instead of skbs as the
elements in RX ring.

[1] https://www.spinics.net/lists/linux-wireless/msg187870.html

Signed-off-by: Jian-Hong Pan <jian-hong@xxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
drivers/net/wireless/realtek/rtw88/pci.c | 132 +++++++++++++----------
drivers/net/wireless/realtek/rtw88/pci.h | 2 +-
2 files changed, 75 insertions(+), 59 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtw88/pci.c b/drivers/net/wireless/realtek/rtw88/pci.c
index 23dd06afef3d..e953010f0179 100644
--- a/drivers/net/wireless/realtek/rtw88/pci.c
+++ b/drivers/net/wireless/realtek/rtw88/pci.c
@@ -111,25 +111,49 @@ static void rtw_pci_free_tx_ring(struct rtw_dev *rtwdev,
tx_ring->r.head = NULL;
}

+static struct rtw_pci_rx_buffer_desc *rtw_pci_get_rx_desc(
+ struct rtw_pci_rx_ring *rx_ring,
+ u32 idx)
+{
+ struct rtw_pci_rx_buffer_desc *buf_desc;
+ u32 desc_sz = rx_ring->r.desc_size;
+
+ buf_desc = (struct rtw_pci_rx_buffer_desc *)(rx_ring->r.head +
+ idx * desc_sz);
+ return buf_desc;
+}
+
+static dma_addr_t rtw_pci_get_rx_bufdma(struct rtw_pci_rx_ring *rx_ring,
+ u32 idx)
+{
+ struct rtw_pci_rx_buffer_desc *buf_desc;
+ dma_addr_t dma;
+
+ buf_desc = rtw_pci_get_rx_desc(rx_ring, idx);
+ dma = le32_to_cpu(buf_desc->dma);
+
+ return dma;
+}
+
static void rtw_pci_free_rx_ring(struct rtw_dev *rtwdev,
struct rtw_pci_rx_ring *rx_ring)
{
struct pci_dev *pdev = to_pci_dev(rtwdev->dev);
- struct sk_buff *skb;
+ u8 *buf;
dma_addr_t dma;
u8 *head = rx_ring->r.head;
int buf_sz = RTK_PCI_RX_BUF_SIZE;
int ring_sz = rx_ring->r.desc_size * rx_ring->r.len;
- int i;
+ u32 i;

for (i = 0; i < rx_ring->r.len; i++) {
- skb = rx_ring->buf[i];
- if (!skb)
+ buf = rx_ring->buf[i];
+ if (!buf)
continue;

- dma = *((dma_addr_t *)skb->cb);
- pci_unmap_single(pdev, dma, buf_sz, PCI_DMA_FROMDEVICE);
- dev_kfree_skb(skb);
+ dma = rtw_pci_get_rx_bufdma(rx_ring, i);
+ pci_unmap_single(pdev, dma, buf_sz, DMA_FROM_DEVICE);
+ devm_kfree(rtwdev->dev, buf);
rx_ring->buf[i] = NULL;
}

@@ -180,27 +204,24 @@ static int rtw_pci_init_tx_ring(struct rtw_dev *rtwdev,
return 0;
}

-static int rtw_pci_reset_rx_desc(struct rtw_dev *rtwdev, struct sk_buff *skb,
- struct rtw_pci_rx_ring *rx_ring,
- u32 idx, u32 desc_sz)
+static int rtw_pci_reset_rx_desc(struct rtw_dev *rtwdev, u8 *buf,
+ struct rtw_pci_rx_ring *rx_ring, u32 idx)
{
struct pci_dev *pdev = to_pci_dev(rtwdev->dev);
struct rtw_pci_rx_buffer_desc *buf_desc;
int buf_sz = RTK_PCI_RX_BUF_SIZE;
dma_addr_t dma;

- if (!skb)
+ if (!buf)
return -EINVAL;

- dma = pci_map_single(pdev, skb->data, buf_sz, PCI_DMA_FROMDEVICE);
+ dma = pci_map_single(pdev, buf, buf_sz, DMA_FROM_DEVICE);
if (pci_dma_mapping_error(pdev, dma))
return -EBUSY;

- *((dma_addr_t *)skb->cb) = dma;
- buf_desc = (struct rtw_pci_rx_buffer_desc *)(rx_ring->r.head +
- idx * desc_sz);
- memset(buf_desc, 0, sizeof(*buf_desc));
+ buf_desc = rtw_pci_get_rx_desc(rx_ring, idx);
buf_desc->buf_size = cpu_to_le16(RTK_PCI_RX_BUF_SIZE);
+ buf_desc->total_pkt_size = cpu_to_le16(0);
buf_desc->dma = cpu_to_le32(dma);

return 0;
@@ -208,7 +229,7 @@ static int rtw_pci_reset_rx_desc(struct rtw_dev *rtwdev, struct sk_buff *skb,

static void rtw_pci_sync_rx_desc_device(struct rtw_dev *rtwdev, dma_addr_t dma,
struct rtw_pci_rx_ring *rx_ring,
- u32 idx, u32 desc_sz)
+ u32 idx)
{
struct device *dev = rtwdev->dev;
struct rtw_pci_rx_buffer_desc *buf_desc;
@@ -216,10 +237,9 @@ static void rtw_pci_sync_rx_desc_device(struct rtw_dev *rtwdev, dma_addr_t dma,

dma_sync_single_for_device(dev, dma, buf_sz, DMA_FROM_DEVICE);

- buf_desc = (struct rtw_pci_rx_buffer_desc *)(rx_ring->r.head +
- idx * desc_sz);
- memset(buf_desc, 0, sizeof(*buf_desc));
+ buf_desc = rtw_pci_get_rx_desc(rx_ring, idx);
buf_desc->buf_size = cpu_to_le16(RTK_PCI_RX_BUF_SIZE);
+ buf_desc->total_pkt_size = cpu_to_le16(0);
buf_desc->dma = cpu_to_le32(dma);
}

@@ -228,12 +248,12 @@ static int rtw_pci_init_rx_ring(struct rtw_dev *rtwdev,
u8 desc_size, u32 len)
{
struct pci_dev *pdev = to_pci_dev(rtwdev->dev);
- struct sk_buff *skb = NULL;
+ u8 *buf = NULL;
dma_addr_t dma;
u8 *head;
int ring_sz = desc_size * len;
int buf_sz = RTK_PCI_RX_BUF_SIZE;
- int i, allocated;
+ u32 i, allocated;
int ret = 0;

head = pci_zalloc_consistent(pdev, ring_sz, &dma);
@@ -242,41 +262,39 @@ static int rtw_pci_init_rx_ring(struct rtw_dev *rtwdev,
return -ENOMEM;
}
rx_ring->r.head = head;
+ rx_ring->r.dma = dma;
+ rx_ring->r.len = len;
+ rx_ring->r.desc_size = desc_size;
+ rx_ring->r.wp = 0;
+ rx_ring->r.rp = 0;

for (i = 0; i < len; i++) {
- skb = dev_alloc_skb(buf_sz);
- if (!skb) {
+ buf = devm_kzalloc(rtwdev->dev, buf_sz, GFP_ATOMIC);
+ if (!buf) {
allocated = i;
ret = -ENOMEM;
goto err_out;
}

- memset(skb->data, 0, buf_sz);
- rx_ring->buf[i] = skb;
- ret = rtw_pci_reset_rx_desc(rtwdev, skb, rx_ring, i, desc_size);
+ rx_ring->buf[i] = buf;
+ ret = rtw_pci_reset_rx_desc(rtwdev, buf, rx_ring, i);
if (ret) {
allocated = i;
- dev_kfree_skb_any(skb);
+ devm_kfree(rtwdev->dev, buf);
goto err_out;
}
}

- rx_ring->r.dma = dma;
- rx_ring->r.len = len;
- rx_ring->r.desc_size = desc_size;
- rx_ring->r.wp = 0;
- rx_ring->r.rp = 0;
-
return 0;

err_out:
for (i = 0; i < allocated; i++) {
- skb = rx_ring->buf[i];
- if (!skb)
+ buf = rx_ring->buf[i];
+ if (!buf)
continue;
- dma = *((dma_addr_t *)skb->cb);
- pci_unmap_single(pdev, dma, buf_sz, PCI_DMA_FROMDEVICE);
- dev_kfree_skb_any(skb);
+ dma = rtw_pci_get_rx_bufdma(rx_ring, i);
+ pci_unmap_single(pdev, dma, buf_sz, DMA_FROM_DEVICE);
+ devm_kfree(rtwdev->dev, buf);
rx_ring->buf[i] = NULL;
}
pci_free_consistent(pdev, ring_sz, head, dma);
@@ -776,13 +794,12 @@ static void rtw_pci_rx_isr(struct rtw_dev *rtwdev, struct rtw_pci *rtwpci,
struct rtw_pci_rx_ring *ring;
struct rtw_rx_pkt_stat pkt_stat;
struct ieee80211_rx_status rx_status;
- struct sk_buff *skb, *new;
+ struct sk_buff *skb;
u32 cur_wp, cur_rp, tmp;
u32 count;
u32 pkt_offset;
u32 pkt_desc_sz = chip->rx_pkt_desc_sz;
- u32 buf_desc_sz = chip->rx_buf_desc_sz;
- u32 new_len;
+ u32 len;
u8 *rx_desc;
dma_addr_t dma;

@@ -799,11 +816,11 @@ static void rtw_pci_rx_isr(struct rtw_dev *rtwdev, struct rtw_pci *rtwpci,
cur_rp = ring->r.rp;
while (count--) {
rtw_pci_dma_check(rtwdev, ring, cur_rp);
- skb = ring->buf[cur_rp];
- dma = *((dma_addr_t *)skb->cb);
+ /* buffer is already filled as rx_desc */
+ rx_desc = ring->buf[cur_rp];
+ dma = rtw_pci_get_rx_bufdma(ring, cur_rp);
dma_sync_single_for_cpu(rtwdev->dev, dma, RTK_PCI_RX_BUF_SIZE,
DMA_FROM_DEVICE);
- rx_desc = skb->data;
chip->ops->query_rx_desc(rtwdev, rx_desc, &pkt_stat, &rx_status);

/* offset from rx_desc to payload */
@@ -813,32 +830,31 @@ static void rtw_pci_rx_isr(struct rtw_dev *rtwdev, struct rtw_pci *rtwpci,
/* allocate a new skb for this frame,
* discard the frame if none available
*/
- new_len = pkt_stat.pkt_len + pkt_offset;
- new = dev_alloc_skb(new_len);
- if (WARN_ONCE(!new, "rx routine starvation\n"))
+ len = pkt_stat.pkt_len + pkt_offset;
+ skb = dev_alloc_skb(len);
+ if (WARN_ONCE(!skb, "rx routine starvation\n"))
goto next_rp;

/* put the DMA data including rx_desc from phy to new skb */
- skb_put_data(new, skb->data, new_len);
+ skb_put_data(skb, rx_desc, len);

if (pkt_stat.is_c2h) {
/* pass rx_desc & offset for further operation */
- *((u32 *)new->cb) = pkt_offset;
- skb_queue_tail(&rtwdev->c2h_queue, new);
+ *((u32 *)skb->cb) = pkt_offset;
+ skb_queue_tail(&rtwdev->c2h_queue, skb);
ieee80211_queue_work(rtwdev->hw, &rtwdev->c2h_work);
} else {
/* remove rx_desc */
- skb_pull(new, pkt_offset);
+ skb_pull(skb, pkt_offset);

- rtw_rx_stats(rtwdev, pkt_stat.vif, new);
- memcpy(new->cb, &rx_status, sizeof(rx_status));
- ieee80211_rx_irqsafe(rtwdev->hw, new);
+ rtw_rx_stats(rtwdev, pkt_stat.vif, skb);
+ memcpy(skb->cb, &rx_status, sizeof(rx_status));
+ ieee80211_rx_irqsafe(rtwdev->hw, skb);
}

next_rp:
- /* new skb delivered to mac80211, re-enable original skb DMA */
- rtw_pci_sync_rx_desc_device(rtwdev, dma, ring, cur_rp,
- buf_desc_sz);
+ /* new skb delivered to mac80211, re-enable original buf DMA */
+ rtw_pci_sync_rx_desc_device(rtwdev, dma, ring, cur_rp);

/* host read next element in ring */
if (++cur_rp >= ring->r.len)
diff --git a/drivers/net/wireless/realtek/rtw88/pci.h b/drivers/net/wireless/realtek/rtw88/pci.h
index 87824a4caba9..283685421a64 100644
--- a/drivers/net/wireless/realtek/rtw88/pci.h
+++ b/drivers/net/wireless/realtek/rtw88/pci.h
@@ -174,7 +174,7 @@ struct rtw_pci_rx_buffer_desc {

struct rtw_pci_rx_ring {
struct rtw_pci_ring r;
- struct sk_buff *buf[RTK_MAX_RX_DESC_NUM];
+ u8 *buf[RTK_MAX_RX_DESC_NUM];
};

#define RX_TAG_MAX 8192
--
2.22.0