[U-Boot] [PATCH v2] serial: ns16550: Add register shift variable

[Alexander Graf]

On 07/17/2018 11:21 AM, Lokesh Vutla wrote:
>
> On Tuesday 17 July 2018 02:42 PM, Alexander Graf wrote:
>> On 07/17/2018 09:55 AM, Lokesh Vutla wrote:
>>> On Tuesday 17 July 2018 12:32 PM, Felix Brack wrote:
>>>> This patch adds a new Kconfig variable that allows setting
>>>> the register offset shift value for the ns16550 driver to some
>>>> other value then 0 if not defined by the DT. All credit for this
>>>> patch goes to Lokesh Vutla as it was his idea.
>>>>
>>>> The motivation for writing this patch originates in the
>>>> effort of synchronizing U-Boot DT to Linux DT for am33xx SOCs.
>>>> The current am33xx.dtsi file from U-Boot defines the <reg-shift>
>>>> property for all UART nodes. The actual (4.18+) am33xx.dtsi
>>>> file from Linux does not define <reg-shift> anymore. To prevent
>>>> (probably difficult) changes in many .dts and .dtsi files once
>>>> the synchronization is done, one can use this new variable. For
>>>> the pdu001 board, for example, SYS_NS16550_REG_SHIFT is set
>>>> to 2; no need to clutter U-Boot and board specific dts files
>>>> with <reg-shift> properties.
>>>>
>>>> Signed-off-by: Felix Brack <fb at ltec.ch>
>> NAK. Please determine the shift value from the compatible instead.
>> Ideally you would create a subclass of the ns16550 device class and set
>> reg_shift in there.
> There was a separate driver for omap_serial initially but was deleted by
> the below commit:
>
> commit c7b9686d5d482c8e952598841ea467e6ec0ec0de
> Author: Thomas Chou <thomas at wytron.com.tw>
> Date:   Thu Nov 19 21:48:12 2015 +0800
>
>      ns16550: unify serial_omap
>
>      Unify serial_omap, and use the generic binding.
>
>      Signed-off-by: Thomas Chou <thomas at wytron.com.tw>
>      Reviewed-by: Tom Rini <trini at konsulko.com>
>      Acked-by: Simon Glass <sjg at chromium.org>

Sounds like that wasn't a terribly smart move :).

If you really don't want a separate driver (and I'm not sure why you 
wouldn't), declare a separate PORT for ti,omap3-uart in 
ns16550_serial_ids and set the shift value based on that in 
ns16550_serial_ofdata_to_platdata() if DT doesn't describe one.


Alex