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Message-ID: <BANLkTim4vunTm1176MRw3pqRZnunu4=9jg@mail.gmail.com>
Date: Tue, 21 Jun 2011 13:13:50 -0600
From: Grant Likely <grant.likely@...retlab.ca>
To: Shawn Guo <shawn.guo@...escale.com>
Cc: patches@...aro.org, netdev@...r.kernel.org,
devicetree-discuss@...ts.ozlabs.org,
Jason Liu <jason.hui@...aro.org>, linux-kernel@...r.kernel.org,
Jeremy Kerr <jeremy.kerr@...onical.com>,
Sascha Hauer <s.hauer@...gutronix.de>,
linux-arm-kernel@...ts.infradead.org,
David Gibson <david@...son.dropbear.id.au>
Subject: Re: [PATCH 1/3] serial/imx: add device tree support
On Tue, Jun 21, 2011 at 7:55 AM, Shawn Guo <shawn.guo@...escale.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@...40000 { /*...*/ };
.... 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@...0c000 {
> + uart2: uart@...0c000 {
> compatible = "fsl,imx51-uart", "fsl,imx21-uart";
> reg = <0x7000c000 0x4000>;
> interrupts = <33>;
> id = <3>;
> - fsl,has-rts-cts;
> + fsl,uart-has-rtscts;
> };
> };
>
> - uart@...bc000 {
> + uart0: uart@...bc000 {
> compatible = "fsl,imx51-uart", "fsl,imx21-uart";
> reg = <0x73fbc000 0x4000>;
> interrupts = <31>;
> id = <1>;
> - fsl,has-rts-cts;
> + fsl,uart-has-rtscts;
> };
>
> - uart@...c0000 {
> + uart1: uart@...c0000 {
> 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.
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