[U-Boot] [PATCH 1/2] i2c: mvtwsi: disable i2c slave on Armada 38x

[Baruch Siach]

Hi Stefan,

On Tue, May 29, 2018 at 08:11:55AM +0200, Stefan Roese wrote:
> On 29.05.2018 06:45, Baruch Siach wrote:
> > Equivalent code that disables the hidden i2c0 slave already exists in
> > the Turris Omnia platform specific code. But this hidden i2c0 slave that
> > interferes the i2c bus is not board specific. Armada 38x SoCs and at
> > least some Kirkwood variants are affected as well. Add code to disable
> > this slave to the i2c bus driver to make it work on all affected
> > hardware.
> > 
> > Use the bind callback because we want this to always run at boot,
> > regardless of whether U-Boot uses the i2c bus.
> > 
> > Cc: Rabeeh Khoury <rabeeh at solid-run.com>
> > Cc: Chris Packham <judge.packham at gmail.com>
> > Reviewed-by: Stefan Roese <sr at denx.de>
> > Reviewed-by: Heiko Schocher <hs at denx.de>
> > Signed-off-by: Baruch Siach <baruch at tkos.co.il>
> > ---

[snip]

> > +static int mvtwsi_i2c_bind(struct udevice *bus)
> > +{
> > +	struct mvtwsi_registers *twsi = devfdt_get_addr_ptr(bus);
> > +
> > +	/* Disable the hidden slave in i2c0 of these platforms */
> > +	if ((IS_ENABLED(CONFIG_ARMADA_38X) || IS_ENABLED(CONFIG_KIRKWOOD))
> 
> We could better use the compatible check here:
> 
> 	if (device_is_compatible(dev, "marvell,mv64xxx-i2c"))

This is not an equivalent check. marvell,mv64xxx-i2c covers other SoCs that 
might not be affected.

Furthermore, this makes a build time test into a run time one. This bloats the 
code for platforms like Allwinner that are unlikely to be affected.

What is the advantage of device_is_compatible()? Is it feasible to build a 
multi-platform U-Boot image?

> > +			&& bus->req_seq == 0)
> > +		twsi_disable_i2c_slave(twsi);
> > +
> > +	return 0;
> > +}

baruch

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