于 2013年07月15日 17:07, Uwe Kleine-König 写道:
Hello,
On Mon, Jul 15, 2013 at 04:41:25PM +0800, Huang Shijie wrote:
于 2013年07月15日 16:27, Uwe Kleine-König 写道:
do you want to say that the driver fails to only enable DMA when RTS/CTS
are available; or that today the driver can handle DMA just fine even
without RTS/CTS? I interpret your commit log as the latter, your patch
implements the former however.
in the mxs-auart, if the RTS/CTS is not invalid, the DMA should be
not enabled.
But current code lost the limit, a uart without the RTS/CTS may also
enables the DMA in which case the uart
may does not run or run in a abnormal way.
So this sounds like a fix that should go into stable and so preferably
should be the first patch in your series.
This patch depends on the first patch. :)
Something like:
serial: mxs-auart: DMA unreliable without RTS/CTS
According to [add some document name here] DMA doesn't work
reliable without hardware handshaking. So make DMA dependant on
a newly introdused property "fsl,uart-has-rtscts".
Cc: stable@xxxxxxxxxx # [first affected version]
The flag is only used to decide if dma should be enabled. So I think an
in-code comment would be nice, too. Is it still correct to set
ok.
AUART_CTRL2_RTSEN and AUART_CTRL2_RTS and read AUART_STAT_CTS when
fsl,uart-has-rtscts is not provided?
i think it's correct. (if i have a imx28-evk board, i can test it.)
If you enable the RTS/CTS from the application, the
tty_port_cts_enabled() will be true.
we will set the AUART_CTRL2_RTSEN in the end when the
"fsl,uart-has-rtscts" is enabled.
(BTW, mxs_auart_set_mctrl has:
u32 ctrl = readl(u->membase + AUART_CTRL2);
ctrl&= ~(AUART_CTRL2_RTSEN | AUART_CTRL2_RTS);
if (mctrl& TIOCM_RTS) {
if (tty_port_cts_enabled(&u->state->port))
ctrl |= AUART_CTRL2_RTSEN;
else
ctrl |= AUART_CTRL2_RTS;
}
s->ctrl = mctrl;
A comment for the diligent reader about the difference between RTSEN and
RTS would be nice. Also I wonder if shadowing mctrl is sensible and used
Please see the spec about the RTSEN and RTS.
RTSEN enable the flow control by the hardware;
RTS enable the flow control by the software.
thanks
Huang Shijie
correctly here.)
Best regards
Uwe
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