serial: sc16is7xx: improve regmap debugfs by using one regmap per port

serial: sc16is7xx: improve regmap debugfs by using one regmap per port

[Hugo Villeneuve]

Hi,
I would like the following patch to be applied to the stable
kernel 6.6:

3837a0379533 serial: sc16is7xx: improve regmap debugfs by using one
regmap per port

As noted in
https://lore.kernel.org/all/20231211171353.2901416-1-hugo@hugovil.com/raw :
---------------------
I did not originally add a "Cc: stable" tag for the above mentioned
commit, as it was intended only to improve debugging using debugfs. But
since then, I have been able to confirm that it also fixes a long
standing bug in our system where the Tx interrupt are no longer enabled
at some point when transmitting large RS-485 paquets that completely
fill the FIFO and thus require multiple and subsequent writes to the
FIFO once space in it becomes available. I have been investigating why,
but so far I haven't found the exact cause, altough I suspect it has
something to do with regmap caching...
---------------------

It applies cleanly and was tested on this kernel using a
custom board with a Variscite IMX8MN NANO SOM, a NewHaven LCD, and two
SC16IS752 on a SPI bus. The four UARTs are using RS-485 mode.

Thank you,
Hugo Villeneuve

Re: serial: sc16is7xx: improve regmap debugfs by using one regmap per port

[Greg KH]

On Tue, Jan 23, 2024 at 12:29:57PM -0500, Hugo Villeneuve wrote:
> Hi,
> I would like the following patch to be applied to the stable
> kernel 6.6:
> 
> 3837a0379533 serial: sc16is7xx: improve regmap debugfs by using one
> regmap per port
> 
> As noted in
> https://lore.kernel.org/all/20231211171353.2901416-1-hugo@hugovil.com/raw :
> ---------------------
> I did not originally add a "Cc: stable" tag for the above mentioned
> commit, as it was intended only to improve debugging using debugfs. But
> since then, I have been able to confirm that it also fixes a long
> standing bug in our system where the Tx interrupt are no longer enabled
> at some point when transmitting large RS-485 paquets that completely
> fill the FIFO and thus require multiple and subsequent writes to the
> FIFO once space in it becomes available. I have been investigating why,
> but so far I haven't found the exact cause, altough I suspect it has
> something to do with regmap caching...
> ---------------------
> 
> It applies cleanly and was tested on this kernel using a
> custom board with a Variscite IMX8MN NANO SOM, a NewHaven LCD, and two
> SC16IS752 on a SPI bus. The four UARTs are using RS-485 mode.

Now queued up, thanks.

greg k-h