| Message ID | 1374739144-732-1-git-send-email-hayeswang@realtek.com |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Hayes Wang <hayeswang@realtek.com> 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 <hayeswang@realtek.com> 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 netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sat, 2013-07-27 at 20:21 -0700, David Miller wrote: > From: Hayes Wang <hayeswang@realtek.com> > 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 <hayeswang@realtek.com> > > 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 netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Oliver Neukum <oneukum@suse.de> Date: Mon, 29 Jul 2013 07:20:24 +0200 > On Sat, 2013-07-27 at 20:21 -0700, David Miller wrote: >> From: Hayes Wang <hayeswang@realtek.com> >> 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 <hayeswang@realtek.com> >> >> 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 netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 &= 0xffff; + ret = __le32_to_cpu(*tmp); + ret >>= (shift * 8); + ret &= 0xffff; - 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 = 0xffff; 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; }
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 <hayeswang@realtek.com> --- drivers/net/usb/r815x.c | 44 +++++++++++++++++++++++++++----------------- 1 file changed, 27 insertions(+), 17 deletions(-)