lkml.org 
[lkml]   [2020]   [Nov]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] ARM: dts: at91: add serial MFD sub-node for usart
On Mon, 02 Nov 2020, Codrin.Ciubotariu@microchip.com wrote:

> On 02.11.2020 11:01, Lee Jones wrote:
> > On Fri, 30 Oct 2020, Nicolas Ferre wrote:
> >
> >> On 30/10/2020 at 12:07, Codrin Ciubotariu wrote:
> >>> The "atmel,at91sam9260-usart" driver is a MFD driver, so it needs sub-nodes
> >>> to match the registered platform device. For this reason, we add a serial
> >>> subnode to all the "atmel,at91sam9260-usart" serial compatible nods. This
> >>> will also remove the boot warning:
> >>> "atmel_usart_serial: Failed to locate of_node [id: -2]"
> >>
> >> I don't remember this warning was raised previously even if the MFD driver
> >> was added a while ago (Sept. 2018).
> >>
> >> I would say it's due to 466a62d7642f ("mfd: core: Make a best effort attempt
> >> to match devices with the correct of_nodes") which was added on mid August
> >> and corrected with 22380b65dc70 ("mfd: mfd-core: Ensure disabled devices are
> >> ignored without error") but maybe not covering our case.
> >>
> >> So, well, I don't know what's the best option to this change. Moreover, I
> >> would say that all other USART related properties go into the child not if
> >> there is a need for one.
> >>
> >> Lee, I suspect that we're not the only ones experiencing this ugly warning
> >> during the boot log: can you point us out how to deal with it for our
> >> existing atmel_serial.c users?
> >
> > You should not be instantiating drivers through Device Tree which are
> > not described there. If the correct representation of the H/W already
> > exists in Device Tree i.e. no SPI and UART IP really exists, use the
> > MFD core API to register them utilising the platform API instead.
> >
> > This should do it:
> >
> > diff --git a/drivers/mfd/at91-usart.c b/drivers/mfd/at91-usart.c
> > index 6a8351a4588e2..939bd2332a4f6 100644
> > --- a/drivers/mfd/at91-usart.c
> > +++ b/drivers/mfd/at91-usart.c
> > @@ -17,12 +17,10 @@
> >
> > static const struct mfd_cell at91_usart_spi_subdev = {
> > .name = "at91_usart_spi",
> > - .of_compatible = "microchip,at91sam9g45-usart-spi",
> > };
> >
> > static const struct mfd_cell at91_usart_serial_subdev = {
> > .name = "atmel_usart_serial",
> > - .of_compatible = "atmel,at91rm9200-usart-serial",
> > };
> >
> > static int at91_usart_mode_probe(struct platform_device *pdev)
>
> [snip]
>
> Hi Lee, thank you for looking through our usart driver and for sharing
> your thoughts. Removing the usage of compatible string means that for
> similar serial/SPI IPs we would need to create new platform drivers.

Why would you need to do that?

> This is not ideal, but it's a solution. What I proposed is more
> flexible, but, as you pointed out, I am not sure it correctly describes
> the HW, because the decision of whether to use this IP as a serial or a
> SPI is a configurable one.
>
> Thanks and best regards,
> Codrin

--
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog

\
 
 \ /
  Last update: 2020-11-02 13:30    [W:1.399 / U:0.456 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site