[PATCH 1/3] serial/imx: add device tree support

[grant.likely@secretlab.ca (Grant Likely)]

On Tue, Jun 21, 2011 at 7:55 AM, Shawn Guo <shawn.guo@freescale.com> wrote:
> Hi Grant,
>
> I just gave a try to use aliases node for identify the device index.
> Please take a look and let me know if it's what you expect.

Thanks Shawn.  This is definitely on track.  Comments below...

>
> On Sun, Jun 19, 2011 at 03:30:02PM +0800, Shawn Guo wrote:
> [...]
>> > >
>> > > +#ifdef CONFIG_OF
>> > > +static int serial_imx_probe_dt(struct imx_port *sport,
>> > > + ? ? ? ? struct platform_device *pdev)
>> > > +{
>> > > + struct device_node *node = pdev->dev.of_node;
>> > > + const __be32 *line;
>> > > +
>> > > + if (!node)
>> > > + ? ? ? ? return -ENODEV;
>> > > +
>> > > + line = of_get_property(node, "id", NULL);
>> > > + if (!line)
>> > > + ? ? ? ? return -ENODEV;
>> > > +
>> > > + sport->port.line = be32_to_cpup(line) - 1;
>> >
>> > Hmmm, I really would like to be rid of this. ?Instead, if uarts must
>> > be enumerated, the driver should look for a /aliases/uart* property
>> > that matches the of_node. ?Doing it that way is already established in
>> > the OpenFirmware documentation, and it ensures there are no overlaps
>> > in the global namespace.
>> >
>>
>> I just gave one more try to avoid using 'aliases', and you gave a
>> 'no' again. ?Now, I know how hard you are on this. ?Okay, I start
>> thinking about your suggestion seriously :)
>>
>> > We do need some infrastructure to make that easier though. ?Would you
>> > have time to help put that together?
>> >
>> Ok, I will give it a try.
>>
>
> diff --git a/arch/arm/boot/dts/imx51-babbage.dts b/arch/arm/boot/dts/imx51-babbage.dts
> index da0381a..f4a5c3c 100644
> --- a/arch/arm/boot/dts/imx51-babbage.dts
> +++ b/arch/arm/boot/dts/imx51-babbage.dts
> @@ -18,6 +18,12 @@
> ? ? ? ?compatible = "fsl,imx51-babbage", "fsl,imx51";
> ? ? ? ?interrupt-parent = <&tzic>;
>
> + ? ? ? aliases {
> + ? ? ? ? ? ? ? serial0 = &uart0;
> + ? ? ? ? ? ? ? serial1 = &uart1;
> + ? ? ? ? ? ? ? serial2 = &uart2;
> + ? ? ? };
> +

Hmmm.  David Gibson had tossed out an idea of automatically generating
aliases from labels.  It may be time to revisit that idea.

David, perhaps using this format for a label should turn it into an
alias (prefix label with an asterisk):

        *thealias: i2c at 12340000 { /*...*/ };

.... although that approach gets *really* hairy when considering that
different boards will want different enumeration.  How would one
override an automatic alias defined by an included .dts file?

> ? ? ? ?chosen {
> ? ? ? ? ? ? ? ?bootargs = "console=ttymxc0,115200 root=/dev/mmcblk0p3 rootwait";
> ? ? ? ?};
> @@ -47,29 +53,29 @@
> ? ? ? ? ? ? ? ? ? ? ? ?reg = <0x70000000 0x40000>;
> ? ? ? ? ? ? ? ? ? ? ? ?ranges;
>
> - ? ? ? ? ? ? ? ? ? ? ? uart at 7000c000 {
> + ? ? ? ? ? ? ? ? ? ? ? uart2: uart at 7000c000 {
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?compatible = "fsl,imx51-uart", "fsl,imx21-uart";
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?reg = <0x7000c000 0x4000>;
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?interrupts = <33>;
> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?id = <3>;
> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? fsl,has-rts-cts;
> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? fsl,uart-has-rtscts;
> ? ? ? ? ? ? ? ? ? ? ? ?};
> ? ? ? ? ? ? ? ?};
>
> - ? ? ? ? ? ? ? uart at 73fbc000 {
> + ? ? ? ? ? ? ? uart0: uart at 73fbc000 {
> ? ? ? ? ? ? ? ? ? ? ? ?compatible = "fsl,imx51-uart", "fsl,imx21-uart";
> ? ? ? ? ? ? ? ? ? ? ? ?reg = <0x73fbc000 0x4000>;
> ? ? ? ? ? ? ? ? ? ? ? ?interrupts = <31>;
> ? ? ? ? ? ? ? ? ? ? ? ?id = <1>;
> - ? ? ? ? ? ? ? ? ? ? ? fsl,has-rts-cts;
> + ? ? ? ? ? ? ? ? ? ? ? fsl,uart-has-rtscts;
> ? ? ? ? ? ? ? ?};
>
> - ? ? ? ? ? ? ? uart at 73fc0000 {
> + ? ? ? ? ? ? ? uart1: uart at 73fc0000 {
> ? ? ? ? ? ? ? ? ? ? ? ?compatible = "fsl,imx51-uart", "fsl,imx21-uart";
> ? ? ? ? ? ? ? ? ? ? ? ?reg = <0x73fc0000 0x4000>;
> ? ? ? ? ? ? ? ? ? ? ? ?interrupts = <32>;
> ? ? ? ? ? ? ? ? ? ? ? ?id = <2>;
> - ? ? ? ? ? ? ? ? ? ? ? fsl,has-rts-cts;
> + ? ? ? ? ? ? ? ? ? ? ? fsl,uart-has-rtscts;
> ? ? ? ? ? ? ? ?};
> ? ? ? ?};
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index 632ebae..13df5d2 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -737,6 +737,37 @@ err0:
> ?EXPORT_SYMBOL(of_parse_phandles_with_args);
>
> ?/**
> + * ? ? of_get_device_index - Get device index by looking up "aliases" node
> + * ? ? @np: ? ?Pointer to device node that asks for device index
> + * ? ? @name: ?The device alias without index number
> + *
> + * ? ? Returns the device index if find it, else returns -ENODEV.
> + */
> +int of_get_device_index(struct device_node *np, const char *alias)
> +{
> + ? ? ? struct device_node *aliases = of_find_node_by_name(NULL, "aliases");
> + ? ? ? struct property *prop;
> + ? ? ? char name[32];
> + ? ? ? int index = 0;
> +
> + ? ? ? if (!aliases)
> + ? ? ? ? ? ? ? return -ENODEV;
> +
> + ? ? ? while (1) {
> + ? ? ? ? ? ? ? snprintf(name, sizeof(name), "%s%d", alias, index);
> + ? ? ? ? ? ? ? prop = of_find_property(aliases, name, NULL);
> + ? ? ? ? ? ? ? if (!prop)
> + ? ? ? ? ? ? ? ? ? ? ? return -ENODEV;
> + ? ? ? ? ? ? ? if (np == of_find_node_by_path(prop->value))
> + ? ? ? ? ? ? ? ? ? ? ? break;
> + ? ? ? ? ? ? ? index++;
> + ? ? ? }

Rather than parsing the alias strings everytime, it would probably be
better to preprocess all the properties in the aliases node and create
a lookup table of alias->node references that can be walked quickly
and trivially.

Also, when obtaining an enumeration for a device, you'll need to be
careful about what number gets returned.  If the node doesn't match a
given alias, but aliases do exist for other devices of like type, then
you need to be careful not to assign a number already assigned to
another device via an alias (this of course assumes the driver
supports dynamics enumeration, which many drivers will).  It would be

\> +
> + ? ? ? return index;
> +}
> +EXPORT_SYMBOL(of_get_device_index);
> +
> +/**
> ?* prom_add_property - Add a property to a node
> ?*/
> ?int prom_add_property(struct device_node *np, struct property *prop)
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index da436e0..852668f 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -1271,18 +1271,18 @@ static int serial_imx_probe_dt(struct imx_port *sport,
> ? ? ? ?struct device_node *node = pdev->dev.of_node;
> ? ? ? ?const struct of_device_id *of_id =
> ? ? ? ? ? ? ? ? ? ? ? ?of_match_device(imx_uart_dt_ids, &pdev->dev);
> - ? ? ? const __be32 *line;
> + ? ? ? int line;
>
> ? ? ? ?if (!node)
> ? ? ? ? ? ? ? ?return -ENODEV;
>
> - ? ? ? line = of_get_property(node, "id", NULL);
> - ? ? ? if (!line)
> + ? ? ? line = of_get_device_index(node, "serial");
> + ? ? ? if (IS_ERR_VALUE(line))
> ? ? ? ? ? ? ? ?return -ENODEV;

Personally, it an alias isn't present, then I'd dynamically assign a port id.

>
> - ? ? ? sport->port.line = be32_to_cpup(line) - 1;
> + ? ? ? sport->port.line = line;
>
> - ? ? ? if (of_get_property(node, "fsl,has-rts-cts", NULL))
> + ? ? ? if (of_get_property(node, "fsl,uart-has-rtscts", NULL))
> ? ? ? ? ? ? ? ?sport->have_rtscts = 1;
>
> ? ? ? ?if (of_get_property(node, "fsl,irda-mode", NULL))
> diff --git a/include/linux/of.h b/include/linux/of.h
> index bfc0ed1..3153752 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -213,6 +213,8 @@ extern int of_parse_phandles_with_args(struct device_node *np,
> ? ? ? ?const char *list_name, const char *cells_name, int index,
> ? ? ? ?struct device_node **out_node, const void **out_args);
>
> +extern int of_get_device_index(struct device_node *np, const char *alias);
> +
> ?extern int of_machine_is_compatible(const char *compat);
>
> ?extern int prom_add_property(struct device_node* np, struct property* prop);
>
> --
> Regards,
> Shawn
>
>



-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.