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Re: [PATCH 0/3] tty: serial: 8250_omap: Enable DMA support

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  Re: [PATCH 0/3] tty: serial: 8250_omap: Enable DMA support Vignesh R <vigneshr@ti.com> - 2017-01-17 07:10 +0100
    Re: [PATCH 0/3] tty: serial: 8250_omap: Enable DMA support Vignesh R <vigneshr@ti.com> - 2017-01-17 11:10 +0100
      Re: [PATCH 0/3] tty: serial: 8250_omap: Enable DMA support Tony Lindgren <tony@atomide.com> - 2017-01-18 00:40 +0100
        Re: [PATCH 0/3] tty: serial: 8250_omap: Enable DMA support Vignesh R <vigneshr@ti.com> - 2017-01-18 14:20 +0100
          Re: [PATCH 0/3] tty: serial: 8250_omap: Enable DMA support Tony Lindgren <tony@atomide.com> - 2017-01-18 18:20 +0100

#1560275 — Re: [PATCH 0/3] tty: serial: 8250_omap: Enable DMA support

On Friday 13 January 2017 11:50 PM, Tony Lindgren wrote:
> * Vignesh R <vigneshr@ti.com> [170113 00:03]:
>> This patch series re enables DMA support for UART 8250_omap driver.
>>
>> Tested on AM335x, AM437x that use EDMA and OMAP5 and DRA74 EVM with
>> SDMA.
> 
> Is 8250_omap serial console working for you on omap5 in general?
> 
> I've noticed that it's really unresponsive for me as if the FIFO
> interrupt was not working. For example logging in might take several
> attempts and a long time with each character showing up much later
> after some timeout.
> 

Yes, I did face the same issue on omap5 using 8250_omap driver for
console. Looks like this bug has existed all along.

> TX on the uart on omap5 seems to work OK, I do see all the console
> messages fine. And these patches do not make the issue better or
> worse.
> 

True.

-- 
Regards
Vignesh

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#1560419

On Tuesday 17 January 2017 11:36 AM, Vignesh R wrote:
> 
> 
> On Friday 13 January 2017 11:50 PM, Tony Lindgren wrote:
>> * Vignesh R <vigneshr@ti.com> [170113 00:03]:
>>> This patch series re enables DMA support for UART 8250_omap driver.
>>>
>>> Tested on AM335x, AM437x that use EDMA and OMAP5 and DRA74 EVM with
>>> SDMA.
>>
>> Is 8250_omap serial console working for you on omap5 in general?
>>
>> I've noticed that it's really unresponsive for me as if the FIFO
>> interrupt was not working. For example logging in might take several
>> attempts and a long time with each character showing up much later
>> after some timeout.
>>
> 
> Yes, I did face the same issue on omap5 using 8250_omap driver for
> console. Looks like this bug has existed all along.
> 

This looks a separate issue, I don't see any errata specific errata wrt
UART on OMAP5. I will try to debug further.

-- 
Regards
Vignesh

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#1561119

* Vignesh R <vigneshr@ti.com> [170117 02:06]:
> 
> 
> On Tuesday 17 January 2017 11:36 AM, Vignesh R wrote:
> > 
> > 
> > On Friday 13 January 2017 11:50 PM, Tony Lindgren wrote:
> >> * Vignesh R <vigneshr@ti.com> [170113 00:03]:
> >>> This patch series re enables DMA support for UART 8250_omap driver.
> >>>
> >>> Tested on AM335x, AM437x that use EDMA and OMAP5 and DRA74 EVM with
> >>> SDMA.
> >>
> >> Is 8250_omap serial console working for you on omap5 in general?
> >>
> >> I've noticed that it's really unresponsive for me as if the FIFO
> >> interrupt was not working. For example logging in might take several
> >> attempts and a long time with each character showing up much later
> >> after some timeout.
> >>
> > 
> > Yes, I did face the same issue on omap5 using 8250_omap driver for
> > console. Looks like this bug has existed all along.
> > 
> 
> This looks a separate issue, I don't see any errata specific errata wrt
> UART on OMAP5. I will try to debug further.

OK maybe it's something configured or not configured by the bootloader
that we're missing in the Linux driver?

Other than the omap5 issue, 8250_OMAP seems to behave on all variants
that I've tried it with so far.

Regards,

Tony

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#1561761

On Wednesday 18 January 2017 04:55 AM, Tony Lindgren wrote:
> * Vignesh R <vigneshr@ti.com> [170117 02:06]:
>>
>>
>> On Tuesday 17 January 2017 11:36 AM, Vignesh R wrote:
>>>
>>>
>>> On Friday 13 January 2017 11:50 PM, Tony Lindgren wrote:
>>>> * Vignesh R <vigneshr@ti.com> [170113 00:03]:
>>>>> This patch series re enables DMA support for UART 8250_omap driver.
>>>>>
>>>>> Tested on AM335x, AM437x that use EDMA and OMAP5 and DRA74 EVM with
>>>>> SDMA.
>>>>
>>>> Is 8250_omap serial console working for you on omap5 in general?
>>>>
>>>> I've noticed that it's really unresponsive for me as if the FIFO
>>>> interrupt was not working. For example logging in might take several
>>>> attempts and a long time with each character showing up much later
>>>> after some timeout.
>>>>
>>>
>>> Yes, I did face the same issue on omap5 using 8250_omap driver for
>>> console. Looks like this bug has existed all along.
>>>
>>
>> This looks a separate issue, I don't see any errata specific errata wrt
>> UART on OMAP5. I will try to debug further.
> 
> OK maybe it's something configured or not configured by the bootloader
> that we're missing in the Linux driver?
> 

omap-serial uses a UART RX FIFO trigger of 1 byte whereas 8250_omap
driver uses a RX FIFO trigger of 48 bytes. If less than 48 bytes is
received then RX Timeout interrupt is raised which will help the driver
to flush the FIFO. It seems like RX timeout does not seem to bring out
UART IP from idle state on OMAP5.

I have posted a fix based on what is done for DRA7 in hwmod code:
http://lists.infradead.org/pipermail/linux-arm-kernel/2017-January/480619.html


-- 
Regards
Vignesh

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#1561975

* Vignesh R <vigneshr@ti.com> [170118 04:04]:
> 
> 
> On Wednesday 18 January 2017 04:55 AM, Tony Lindgren wrote:
> > * Vignesh R <vigneshr@ti.com> [170117 02:06]:
> >>
> >>
> >> On Tuesday 17 January 2017 11:36 AM, Vignesh R wrote:
> >>>
> >>>
> >>> On Friday 13 January 2017 11:50 PM, Tony Lindgren wrote:
> >>>> * Vignesh R <vigneshr@ti.com> [170113 00:03]:
> >>>>> This patch series re enables DMA support for UART 8250_omap driver.
> >>>>>
> >>>>> Tested on AM335x, AM437x that use EDMA and OMAP5 and DRA74 EVM with
> >>>>> SDMA.
> >>>>
> >>>> Is 8250_omap serial console working for you on omap5 in general?
> >>>>
> >>>> I've noticed that it's really unresponsive for me as if the FIFO
> >>>> interrupt was not working. For example logging in might take several
> >>>> attempts and a long time with each character showing up much later
> >>>> after some timeout.
> >>>>
> >>>
> >>> Yes, I did face the same issue on omap5 using 8250_omap driver for
> >>> console. Looks like this bug has existed all along.
> >>>
> >>
> >> This looks a separate issue, I don't see any errata specific errata wrt
> >> UART on OMAP5. I will try to debug further.
> > 
> > OK maybe it's something configured or not configured by the bootloader
> > that we're missing in the Linux driver?
> > 
> 
> omap-serial uses a UART RX FIFO trigger of 1 byte whereas 8250_omap
> driver uses a RX FIFO trigger of 48 bytes. If less than 48 bytes is
> received then RX Timeout interrupt is raised which will help the driver
> to flush the FIFO. It seems like RX timeout does not seem to bring out
> UART IP from idle state on OMAP5.
> 
> I have posted a fix based on what is done for DRA7 in hwmod code:
> http://lists.infradead.org/pipermail/linux-arm-kernel/2017-January/480619.html

OK great, thanks for fixing that! Will give it a try a bit later today.

Regards,

Tony

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