On Fri, 25 Apr 2014, Jon Ringle wrote:
> On Fri, Apr 25, 2014 at 9:44 AM, Charles Coldwell <coldwell@xxxxxxxxx> wrote:
> > On Fri, 25 Apr 2014, Charles Coldwell wrote:
> >
> >> On Thu, 24 Apr 2014, jon@xxxxxxxxxx wrote:
> >>
> >> > diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
> >>
> >> Isn't this a lot of duplication?
> >
> > Actually, the whole thing seems like duplication to me.
>
> The fact that we need to reach over the SPI/I2C bus makes a big
> difference in the way access is handled.
>
> To achieve acceptable throughput, it is necessary to use threaded irq
> and also bulk i2c transfers for RX and TX using
> regmap_raw_{read,write}() to optimize the use of the i2c bus.
Fair enough, but the 8250 framework does allow you to insert your own
irq service routine. "serial8250_default_handle_irq" is the default
(unsurprisingly), but if the uart_port has a non-NULL "handle_irq"
method it will be faithfully copied into the uart_8250_port
"handle_irq" method in 8250_core.c:early_serial_setup.
> This is not a good fit for 8250.
If that's really true, then I would say it argues in favor of a
revision of the 8250 code. Certainly, this is not the last time that
a 16550-compatible UART will appear on a non-PCI, non-ISA bus.
--
Charles M. Coldwell, W1CMC
"Turn on, log in, tune out"
Somerville, Massachusetts, New England (FN42kj)
GPG ID: 852E052F
GPG FPR: 77E5 2B51 4907 F08A 7E92 DE80 AFA9 9A8F 852E 052F
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