Re: [PATCH v2 1/3] net/usb/r815x: replace USB buffer from stack to DMA-able
From: Oliver Neukum Date: Mon, 29 Jul 2013 07:20:24 +0200 > On Sat, 2013-07-27 at 20:21 -0700, David Miller wrote: >> From: Hayes Wang >> Date: Thu, 25 Jul 2013 15:59:02 +0800 >> >> > Some USB buffers use stack which may not be DMA-able. >> > Use the buffers from kmalloc to replace those one. >> > >> > Signed-off-by: Hayes Wang >> >> I don't think it's reasonable to kmalloc() a small integer every time >> you want to use a USB message transfer to read or write chip >> registers. >> >> Instead, add a scratch buffer to struct r8152 which is allocated once >> at driver attach time and which you can use for the transfers. >> >> I think you only need an array of two u32's so something like: >> >> u32 transfer_buf[2]; >> >> ought to be sufficient. > > We cannot do that. It would violate the rules about DMA coherency. > We must not touch the same cacheline while DMA is in operation. Good point, then it'll need to be: u32 *transfer_buf; and allocated appropriately. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v2 1/3] net/usb/r815x: replace USB buffer from stack to DMA-able
On Sat, 2013-07-27 at 20:21 -0700, David Miller wrote: > From: Hayes Wang > Date: Thu, 25 Jul 2013 15:59:02 +0800 > > > Some USB buffers use stack which may not be DMA-able. > > Use the buffers from kmalloc to replace those one. > > > > Signed-off-by: Hayes Wang > > I don't think it's reasonable to kmalloc() a small integer every time > you want to use a USB message transfer to read or write chip > registers. > > Instead, add a scratch buffer to struct r8152 which is allocated once > at driver attach time and which you can use for the transfers. > > I think you only need an array of two u32's so something like: > > u32 transfer_buf[2]; > > ought to be sufficient. We cannot do that. It would violate the rules about DMA coherency. We must not touch the same cacheline while DMA is in operation. Regards Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v2 1/3] net/usb/r815x: replace USB buffer from stack to DMA-able
From: Hayes Wang Date: Thu, 25 Jul 2013 15:59:02 +0800 > Some USB buffers use stack which may not be DMA-able. > Use the buffers from kmalloc to replace those one. > > Signed-off-by: Hayes Wang I don't think it's reasonable to kmalloc() a small integer every time you want to use a USB message transfer to read or write chip registers. Instead, add a scratch buffer to struct r8152 which is allocated once at driver attach time and which you can use for the transfers. I think you only need an array of two u32's so something like: u32 transfer_buf[2]; ought to be sufficient. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH v2 1/3] net/usb/r815x: replace USB buffer from stack to DMA-able
Some USB buffers use stack which may not be DMA-able.
Use the buffers from kmalloc to replace those one.
Signed-off-by: Hayes Wang
---
drivers/net/usb/r815x.c | 44 +++-
1 file changed, 27 insertions(+), 17 deletions(-)
diff --git a/drivers/net/usb/r815x.c b/drivers/net/usb/r815x.c
index 8523922..e9b99ba 100644
--- a/drivers/net/usb/r815x.c
+++ b/drivers/net/usb/r815x.c
@@ -24,34 +24,43 @@
static int pla_read_word(struct usb_device *udev, u16 index)
{
- int data, ret;
+ int ret;
u8 shift = index & 2;
- __le32 ocp_data;
+ __le32 *tmp;
+
+ tmp = kmalloc(sizeof(*tmp), GFP_KERNEL);
+ if (!tmp)
+ return -ENOMEM;
index &= ~3;
ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
RTL815x_REQ_GET_REGS, RTL815x_REQT_READ,
- index, MCU_TYPE_PLA, &ocp_data, sizeof(ocp_data),
- 500);
+ index, MCU_TYPE_PLA, tmp, sizeof(*tmp), 500);
if (ret < 0)
- return ret;
+ goto out2;
- data = __le32_to_cpu(ocp_data);
- data >>= (shift * 8);
- data &= 0x;
+ ret = __le32_to_cpu(*tmp);
+ ret >>= (shift * 8);
+ ret &= 0x;
- return data;
+out2:
+ kfree(tmp);
+ return ret;
}
static int pla_write_word(struct usb_device *udev, u16 index, u32 data)
{
- __le32 ocp_data;
+ __le32 *tmp;
u32 mask = 0x;
u16 byen = BYTE_EN_WORD;
u8 shift = index & 2;
int ret;
+ tmp = kmalloc(sizeof(*tmp), GFP_KERNEL);
+ if (!tmp)
+ return -ENOMEM;
+
data &= mask;
if (shift) {
@@ -63,19 +72,20 @@ static int pla_write_word(struct usb_device *udev, u16
index, u32 data)
ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
RTL815x_REQ_GET_REGS, RTL815x_REQT_READ,
- index, MCU_TYPE_PLA, &ocp_data, sizeof(ocp_data),
- 500);
+ index, MCU_TYPE_PLA, tmp, sizeof(*tmp), 500);
if (ret < 0)
- return ret;
+ goto out3;
- data |= __le32_to_cpu(ocp_data) & ~mask;
- ocp_data = __cpu_to_le32(data);
+ data |= __le32_to_cpu(*tmp) & ~mask;
+ *tmp = __cpu_to_le32(data);
ret = usb_control_msg(udev, usb_sndctrlpipe(udev, 0),
RTL815x_REQ_SET_REGS, RTL815x_REQT_WRITE,
- index, MCU_TYPE_PLA | byen, &ocp_data,
- sizeof(ocp_data), 500);
+ index, MCU_TYPE_PLA | byen, tmp, sizeof(*tmp),
+ 500);
+out3:
+ kfree(tmp);
return ret;
}
--
1.8.3.1
--
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