[PATCH v2] Revert "serial: 8250_dma: don't bother DMA with small transfers"

[PATCH v2] Revert "serial: 8250_dma: don't bother DMA with small transfers"

[Frederic Danis]

This reverts commit 9119fba0cfeda6d415c9f068df66838a104b87cb.

This commit prevents from sending "big" file using Bluetooth.
When sending a lot of data quickly through the Bluetooth interface, and
after a variable amount of data sent, transfer fails with error:
    kernel: [  415.247453] Bluetooth: hci0 hardware error 0x00

Found on T100TA.

After reverting this commit, send works fine for any file size.

Signed-off-by: Frederic Danis <frederic.danis@linux.intel.com>
---
v2: Re-send to correct people

 drivers/tty/serial/8250/8250_dma.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_dma.c b/drivers/tty/serial/8250/8250_dma.c
index b503071..78259d3 100644
--- a/drivers/tty/serial/8250/8250_dma.c
+++ b/drivers/tty/serial/8250/8250_dma.c
@@ -77,10 +77,6 @@ int serial8250_tx_dma(struct uart_8250_port *p)
 		return 0;
 
 	dma->tx_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
-	if (dma->tx_size < p->port.fifosize) {
-		ret = -EINVAL;
-		goto err;
-	}
 
 	desc = dmaengine_prep_slave_single(dma->txchan,
 					   dma->tx_addr + xmit->tail,
-- 
1.9.1

Re: [PATCH v2] Revert "serial: 8250_dma: don't bother DMA with small transfers"

[Greg KH]

On Tue, Oct 06, 2015 at 03:08:40PM +0200, Frederic Danis wrote:
> This reverts commit 9119fba0cfeda6d415c9f068df66838a104b87cb.
> 
> This commit prevents from sending "big" file using Bluetooth.
> When sending a lot of data quickly through the Bluetooth interface, and
> after a variable amount of data sent, transfer fails with error:
>     kernel: [  415.247453] Bluetooth: hci0 hardware error 0x00
> 
> Found on T100TA.
> 
> After reverting this commit, send works fine for any file size.
> 
> Signed-off-by: Frederic Danis <frederic.danis@linux.intel.com>
> ---
> v2: Re-send to correct people
> 
>  drivers/tty/serial/8250/8250_dma.c | 4 ----
>  1 file changed, 4 deletions(-)

Andy, any objections?

Frederic, don't you want to see this backported to 4.0 and newer?

thanks,

greg k-h

Re: [PATCH v2] Revert "serial: 8250_dma: don't bother DMA with small transfers"

[Frederic Danis]

Hello Greg,

On 06/10/2015 15:55, Greg KH wrote:
> On Tue, Oct 06, 2015 at 03:08:40PM +0200, Frederic Danis wrote:
>> This reverts commit 9119fba0cfeda6d415c9f068df66838a104b87cb.
>>
>> This commit prevents from sending "big" file using Bluetooth.
>> When sending a lot of data quickly through the Bluetooth interface, and
>> after a variable amount of data sent, transfer fails with error:
>>      kernel: [  415.247453] Bluetooth: hci0 hardware error 0x00
>>
>> Found on T100TA.
>>
>> After reverting this commit, send works fine for any file size.
>>
>> Signed-off-by: Frederic Danis <frederic.danis@linux.intel.com>
>> ---
>> v2: Re-send to correct people
>>
>>   drivers/tty/serial/8250/8250_dma.c | 4 ----
>>   1 file changed, 4 deletions(-)
>
> Andy, any objections?
>
> Frederic, don't you want to see this backported to 4.0 and newer?

Yes, you're right, unless Andy has any objection this should be good

Regards

Fred

Re: [PATCH v2] Revert "serial: 8250_dma: don't bother DMA with small transfers"

[Andy Shevchenko]

On Tue, 2015-10-06 at 14:55 +0100, Greg KH wrote:
> On Tue, Oct 06, 2015 at 03:08:40PM +0200, Frederic Danis wrote:
> > This reverts commit 9119fba0cfeda6d415c9f068df66838a104b87cb.
> > 
> > This commit prevents from sending "big" file using Bluetooth.
> > When sending a lot of data quickly through the Bluetooth interface, 
> > and
> > after a variable amount of data sent, transfer fails with error:
> >     kernel: [  415.247453] Bluetooth: hci0 hardware error 0x00
> > 
> > Found on T100TA.
> > 
> > After reverting this commit, send works fine for any file size.
> > 
> > Signed-off-by: Frederic Danis <frederic.danis@linux.intel.com>
> > ---
> > v2: Re-send to correct people
> > 
> >  drivers/tty/serial/8250/8250_dma.c | 4 ----
> >  1 file changed, 4 deletions(-)
> 
> Andy, any objections?

No.

P.S. Unfortunately it's not easy to reproduce on our side, so I trust
Frederic on this.

> 
> Frederic, don't you want to see this backported to 4.0 and newer?
> 
> thanks,
> 
> greg k-h

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy

Re: [PATCH v2] Revert "serial: 8250_dma: don't bother DMA with small transfers"

[Frederic Danis]

Hello Greg,

On 06/10/2015 16:23, Frederic Danis wrote:
>>
>> Andy, any objections?
>>
>> Frederic, don't you want to see this backported to 4.0 and newer?
>
> Yes, you're right, unless Andy has any objection this should be good

This is first time for me that patch may be applied to previous kernel.

Is there something specific I should do to allow this patch to be 
applied and backported to 4.0 and newer ?

Regards

Fred

-- 
Frederic Danis                            Open Source Technology Center
frederic.danis@intel.com                              Intel Corporation

Re: [PATCH v2] Revert "serial: 8250_dma: don't bother DMA with small transfers"

[Andy Shevchenko]

On Fri, 2015-10-09 at 16:45 +0200, Frederic Danis wrote:
> Hello Greg,
> 
> On 06/10/2015 16:23, Frederic Danis wrote:
> > > 
> > > Andy, any objections?
> > > 
> > > Frederic, don't you want to see this backported to 4.0 and newer?
> > 
> > Yes, you're right, unless Andy has any objection this should be 
> > good
> 
> This is first time for me that patch may be applied to previous 
> kernel.
> 
> Is there something specific I should do to allow this patch to be 
> applied and backported to 4.0 and newer ?

Earlier we use to Cc: stable@vger.kernel.org
(I don't know if it's still a case)

Now the tag Fixes: is in use, like you may add the following line to th
e commit message:

Fixes: 9119fba0cfed (serial: 8250_dma: don't bother DMA with small
transfers)

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy

Re: [PATCH v2] Revert "serial: 8250_dma: don't bother DMA with small transfers"

[Fabio Estevam]

On Fri, Oct 9, 2015 at 11:45 AM, Frederic Danis
<frederic.danis@linux.intel.com> wrote:

> This is first time for me that patch may be applied to previous kernel.
>
> Is there something specific I should do to allow this patch to be applied
> and backported to 4.0 and newer ?

You can find the instructions at Documentation/stable_kernel_rules.txt