Re: [PATCH v2 1/3] arm64: imx8mq: add imx8mq iomux-gpr field defines

[Guido Günther]

Hi Arnd,
On Tue, Aug 13, 2019 at 10:08:44AM +0200, Arnd Bergmann wrote:
> On Fri, Aug 9, 2019 at 6:24 PM Guido Günther <agx@xxxxxxxxxxx> wrote:
> >
> > This adds all the gpr registers and the define needed for selecting
> > the input source in the imx-nwl drm bridge.
> >
> > Signed-off-by: Guido Günther <agx@xxxxxxxxxxx>
> > +
> > +#define IOMUXC_GPR0    0x00
> > +#define IOMUXC_GPR1    0x04
> > +#define IOMUXC_GPR2    0x08
> > +#define IOMUXC_GPR3    0x0c
> > +#define IOMUXC_GPR4    0x10
> > +#define IOMUXC_GPR5    0x14
> > +#define IOMUXC_GPR6    0x18
> > +#define IOMUXC_GPR7    0x1c
> (more of the same)
> 
> huh?

These are the names from the imx8MQ reference manual (general purpose
registers, they lump together all sorts of things), it's the same on
imx6/imx7):

    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/mfd/syscon/imx6q-iomuxc-gpr.h
    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/mfd/syscon/imx7-iomuxc-gpr.h     

> > +/* i.MX8Mq iomux gpr register field defines */
> > +#define IMX8MQ_GPR13_MIPI_MUX_SEL              BIT(2)
> 
> I think this define should probably be local to the pinctrl driver, to
> ensure that no other drivers fiddle with the registers manually.

The purpose of these bits is for a driver to fiddle with them to select
the input source. Similar on imx7 it's already used for e.g. the phy
refclk in the pci controller:

    https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/controller/dwc/pci-imx6.c#n638

The GPRs are not about pad configuration but gather all sorts of things
(section 8.2.4 of the imx8mq reference manual): pcie setup, dsi related
bits so I don't think this should be done via a pinctrl
driver. Should we handle that differently than on imx6/7?

Cheers,
 -- Guido