[U-Boot] QUERY:U-boot DM:SERIAL:Multiple On-chip UART Controller Support

[Simon Glass]

Hi,

On 23 May 2018 at 12:04, Simon Glass <sjg at chromium.org> wrote:
> On 23 May 2018 at 11:56, Vabhav Sharma <vabhav.sharma at nxp.com> wrote:
>> Hello Everyone,
>>
>> I am working on integrating  generic PL011 driver in u-boot and linux for

Note, it is 'U-Boot'

>> ARMv8 NXP SoC and facing issue with multiple UART console enablement in
>> u-boot using DM model
>>
>> Kindly provide your valuable feedback and experts comments.
>>
>>
>>
>> DTS require stdout-path(e.g-UART0) to the /chosen device tree node
>> ,Accordingly controller(UART0) is probed/initialized as boot console
>>
>> On u-boot prompt, Bootargs is modified to use UART1(ttyAMA1) console for
>> linux boot but kernel hangs after “Starting kernel ... print”
>>
>>
>>
>> After debugging it’s found that UART1 is not initialized and single(first)
>> controller is  probed/initialized in u-boot (Irrespective of 4 UART nodes
>> are enabled in dts)
>>
>> In drivers/serial/serial-uclass.c ,gd->cur_serial_dev is updated to the DT
>> stdout-path or CONFIG_CONS_INDEX or platform data(first index)
>>
>>
>>
>> Does the u-boot DM model support only one or multiple UART driver
>> probing/initialization? Is there any configuration parameter required to
>> define number of UART controllers to be probed/initialized.
>>
>> This looks limitation as same boot console is used for u-boot and linux and
>> unable to use all available UART controllers.
>>
>>
>>
>> I am new to u-boot and please correct any misunderstanding
>>
>> Let me know If I can submit a patch for multiple UART probe in serial-uclass
>> or open a bug for multiple UART support in u-boot DM model

You can probe additional serial drivers if you like. U-Boot only
probes things in a 'lazy' manner so far. Perhaps you could submit a
patch which probes all serial devices? That is just a case of using
uclass_first_device()...uclass_next_device() to iterate through them.
I suppose we could have a CONFIG option to enable this.

>>
>>
>>
>> PS:I am unable to find owner of serial uclass driver from MAINTAINERS file

Not guilty but I did port a lot of things to driver model.

>>
>>
>>
>> Regards,
>>
>> Vabhav
>>
>>

Regards,
Simon