Re: [PATCHv1 1/3] OMAP UART: Adds omap-serial driver support.

[kishore kadiyala <kishorek.kadiyala@gmail.com>]

Tony,

On Fri, Oct 9, 2009 at 11:16 PM, Tony Lindgren <tony@atomide.com> wrote:
> * G, Manjunath Kondaiah <manjugk@ti.com> [091008 00:41]:
>>
>> Govind,
>> > -----Original Message-----
>> > From: linux-omap-owner@vger.kernel.org
>> > [mailto:linux-omap-owner@vger.kernel.org] On Behalf Of Govindraj
>> > Sent: Thursday, October 08, 2009 11:44 AM
>> > To: Tony Lindgren
>> > Cc: Raja, Govindraj; linux-omap@vger.kernel.org;
>> > linux-kernel@vger.kernel.org; linux-serial@vger.kernel.org
>> > Subject: Re: [PATCHv1 1/3] OMAP UART: Adds omap-serial driver support.
>> >
>> > On Thu, Oct 8, 2009 at 3:21 AM, Tony Lindgren
>> > <tony@atomide.com> wrote:
>> > > * Govindraj.R <govindraj.raja@ti.com> [090924 03:29]:
>> > >> From: Govindraj R <govindraj.raja@ti.com>
>> > >>
>> > >> This patch adds support for OMAP3430-HIGH SPEED UART Controller.
>> > >>
>> > >> Signed-off-by:        Govindraj R <govindraj.raja@ti.com>
>> > >> Reviewed-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
>> > >> Reviewed-by: Tony Lindgren <tony@atomide.com>
>> > >
>> > > You should only add Reviewed-by if Alan or me have replied with it.
>> > >
>> > > So far I've only replied with some comments that have not yet
>> > > been fixed, so we're few more steps from being Reviewd-by.
>> > >
>> > > <snip>
>> > >
>> > >> diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
>> > >> index 6553833..67a7129 100644
>> > >> --- a/drivers/serial/Kconfig
>> > >> +++ b/drivers/serial/Kconfig
>> > >> @@ -1359,6 +1359,53 @@ config SERIAL_OF_PLATFORM
>> > >>         Currently, only 8250 compatible ports are supported, but
>> > >>         others can easily be added.
>> > >>
>> > >> +config SERIAL_OMAP
>> > >> +     bool "OMAP serial port support"
>> > >> +     depends on ARM && ARCH_OMAP
>> > >> +     select SERIAL_CORE
>> > >> +     help
>> > >> +     If you have a machine based on an Texas Instruments
>> > OMAP CPU you
>> > >> +     can enable its onboard serial ports by enabling this option.
>> > >> +
>> > >> +config SERIAL_OMAP_CONSOLE
>> > >> +     bool "Console on OMAP serial port"
>> > >> +     depends on SERIAL_OMAP
>> > >> +     select SERIAL_CORE_CONSOLE
>> > >> +     help
>> > >> +     If you have enabled the serial port on the Texas
>> > Instruments OMAP
>> > >> +     CPU you can make it the console by answering Y to
>> > this option.
>> > >> +
>> > >> +     Even if you say Y here, the currently visible virtual console
>> > >> +     (/dev/tty0) will still be used as the system console
>> > by default, but
>> > >> +     you can alter that using a kernel command line option such as
>> > >> +     "console=ttyS0". (Try "man bootparam" or see the
>> > documentation of
>> > >> +     your boot loader (lilo or loadlin) about how to pass
>> > options to the
>> > >> +     kernel at boot time.)
>> > >> +
>> > >> +config SERIAL_OMAP_DMA_UART1
>> > >> +     bool "UART1 DMA support"
>> > >> +     depends on SERIAL_OMAP
>> > >> +     help
>> > >> +     If you have enabled the serial port on the Texas
>> > Instruments OMAP
>> > >> +     CPU you can enable the DMA transfer on UART 1 by answering
>> > >> +     to this option.
>> > >> +
>> > >> +config SERIAL_OMAP_DMA_UART2
>> > >> +     bool "UART2 DMA support"
>> > >> +     depends on SERIAL_OMAP
>> > >> +     help
>> > >> +     If you have enabled the serial port on the Texas
>> > Instruments OMAP
>> > >> +     CPU you can enable the DMA transfer on UART 2 by answering
>> > >> +     to this option.
>> > >> +
>> > >> +config SERIAL_OMAP_DMA_UART3
>> > >> +     bool "UART3 DMA support"
>> > >> +     depends on SERIAL_OMAP
>> > >> +     help
>> > >> +     If you have enabled the serial port on the Texas
>> > Instruments OMAP
>> > >> +     CPU you can enable the DMA transfer on UART 3 by answering
>> > >> +     to this option.
>> > >> +
>> > >>  config SERIAL_OF_PLATFORM_NWPSERIAL
>> > >>       tristate "NWP serial port driver"
>> > >>       depends on PPC_OF && PPC_DCR
>> > >
>> > > There's absolutely no need for having Kconfig options for the DMA
>> > > support. Please pass that in platform_data from the board-*.c files.
>> > >
>> > > This is the third time I'm commenting on the same issue!
>> > >
>> > > What's the point of posting these patches for review if the issues
>> > > don't get solved?
>> >
>> >
>> > The omap-serial uart driver is designed to work either in interrupt
>> > mode or in DMA mode,
>> > We have provided this option so that one can select interrupt mode or
>> > DMA mode based on the uart usage, if somebody is using uart as console
>> > then interrupt mode will do, else if used with bluetooth which does
>> > huge data transfer then DMA mode can be selected.
>> >
>> > Don't you think this should be a configurable option using kconfig
>> > rather than passing as platform data?
>
> Nope. I think it should be platform_data and should be possible to override
> vith a kernel cmdline option. That's because we support compiling in and
> booting many boards the same kernel binary.
>
>> > if used as platform data then one has to modify platform data to
>> > switch between the interrupt and DMA mode.
>
> How about set some kernel cmdline options if you want to override the
> default settings?

   Using cmdline options, will make specific UART switch  dynamically
   between Non-DMA and DMA mode which is not handled in the driver.

   how abt using bootargs to share this Mode info ?

>
>> Usage of UART is board dependent. It's usage will not change dynamically for
>> a given board. This can be removed from Kconfig and move it to respective
>> board file-> board-*.c
>
> Or can be changed from kernel cmdline if necessary.
>
> Regards,
>
> Tony
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