On Tue, Nov 16, 2021 at 06:14:23AM +0000, Tudor.Ambarus@xxxxxxxxxxxxx wrote:
> On 11/15/21 5:58 PM, Greg KH wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> >
> > On Mon, Nov 15, 2021 at 04:30:04PM +0200, Tudor Ambarus wrote:
> >> dma_cookie_t < 0 indicates an error code, check for it.
> >
> > Very odd changelog text, please be more descriptive about what is
> > happening here.
> >
>
> The tx_submit() method of struct dma_async_tx_descriptor is entitled to do
> sanity checks and return errors if encountered. It's not the case for the
> DMA controller drivers that this client is using (at_h/xdmac), because they
> currently don't do sanity checks and always return a positive cookie at
> tx_submit() method. In case the controller drivers will implement sanity
> checks and return errors, print a message so that the client will be informed
> that something went wrong at tx_submit() level.
>
> >>
> >> Signed-off-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
> >> ---
> >> drivers/tty/serial/atmel_serial.c | 10 ++++++++++
> >> 1 file changed, 10 insertions(+)
> >>
> >> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> >> index 2c99a47a2535..376f7a9c2868 100644
> >> --- a/drivers/tty/serial/atmel_serial.c
> >> +++ b/drivers/tty/serial/atmel_serial.c
> >> @@ -1004,6 +1004,11 @@ static void atmel_tx_dma(struct uart_port *port)
> >> desc->callback = atmel_complete_tx_dma;
> >> desc->callback_param = atmel_port;
> >> atmel_port->cookie_tx = dmaengine_submit(desc);
> >> + if (dma_submit_error(atmel_port->cookie_tx)) {
> >> + dev_err(port->dev, "dma_submit_error %d\n",
> >> + atmel_port->cookie_tx);
> >> + return;
> >
> > What can a user do with this error message?
> >
> will be informed that something went wrong at tx_submit() level.
>
> > Have you seen this happen in real life?
>
> No. I debugged a locking problem and I observed that dma_submit_error() is not called,
> so I thought to update this.
>
> >
> > What commit does this "fix"?
>
> This is rather an improvement, but if you're looking for a fixes tag, I think
> we can use:
> Fixes: 08f738be88bb ("serial: at91: add tx dma support")
>
> I'll send a v2 as part of a bigger series. If you find this patch does not worth it,
> I can as well drop it.
Please resend it because as-is, I can not take it.
thanks,
greg k-h
