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Date: Wed, 10 Apr 2013 20:50:19 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Andreas Larsson <andreas@...sler.com>
Cc: Grant Likely <grant.likely@...retlab.ca>,
Rob Herring <rob.herring@...xeda.com>,
Anton Vorontsov <anton.vorontsov@...aro.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"devicetree-discuss@...ts.ozlabs.org"
<devicetree-discuss@...ts.ozlabs.org>, software@...sler.com
Subject: Re: [PATCH v5 2/3] gpio: grgpio: Add device driver for GRGPIO cores
On Fri, Mar 15, 2013 at 2:45 PM, Andreas Larsson <andreas@...sler.com> wrote:
> This driver supports GRGPIO gpio cores available in the GRLIB VHDL IP
> core library from Aeroflex Gaisler.
>
> Signed-off-by: Andreas Larsson <andreas@...sler.com>
> ---
> .../devicetree/bindings/gpio/gpio-grgpio.txt | 24 +++
> drivers/gpio/Kconfig | 9 ++
> drivers/gpio/Makefile | 1 +
> drivers/gpio/gpio-grgpio.c | 164 ++++++++++++++++++++
> 4 files changed, 198 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/gpio/gpio-grgpio.txt
> create mode 100644 drivers/gpio/gpio-grgpio.c
>
> diff --git a/Documentation/devicetree/bindings/gpio/gpio-grgpio.txt b/Documentation/devicetree/bindings/gpio/gpio-grgpio.txt
> new file mode 100644
> index 0000000..1050dc8
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/gpio/gpio-grgpio.txt
> @@ -0,0 +1,24 @@
> +Aeroflex Gaisler GRGPIO General Purpose I/O cores.
> +
> +The GRGPIO GPIO core is available in the GRLIB VHDL IP core library.
> +
> +Note: In the ordinary environment for the GRGPIO core, a Leon SPARC system,
> +these properties are built from information in the AMBA plug&play.
> +
> +Required properties:
> +
> +- name : Should be "GAISLER_GPIO" or "01_01a"
What is this? Don't we usually use a .compatible string for this?
Name? Que? Is that something legacy?
I would prefer:
- Add you vendor prefix to Documentation/devicetree/bindings/vendor-prefixes.txt
- Use a compatible string like this "gaisler,gpio"
> +- reg : Address and length of the register set for the device
> +
> +- interrupts : Interrupt numbers for this device
> +
> +Optional properties:
> +
> +- base : The base gpio number for the core. A dynamic base is used if not
> + present
This has to go. We don't hardcode numbers from the global GPIO
space into the device tree, beacause as you soon realize this is
Linux-specific and the device tree shall be OS agnostic.
The discussion has come up a number of times, review the mailing
lists for suggestions on how to get around this.
(...)
> +++ b/drivers/gpio/gpio-grgpio.c
> +struct grgpio_regs {
> + u32 data; /* 0x00 */
> + u32 output; /* 0x04 */
> + u32 dir; /* 0x08 */
> + u32 imask; /* 0x0c */
> + u32 ipol; /* 0x10 */
> + u32 iedge; /* 0x14 */
> + u32 bypass; /* 0x18 */
> + u32 __reserved; /* 0x1c */
> + u32 imap[8]; /* 0x20-0x3c */
> +};
Um... Why are you doing this?
> +struct grgpio_priv {
> + struct bgpio_chip bgc;
> + struct grgpio_regs __iomem *regs;
And that's tagged as __iomem * as well, that is very unorthodox.
The usual practice is to have a base pointer void __iomem *base
and offset from that.
> + struct device *dev;
> +};
> +
> +static inline struct grgpio_priv *grgpio_gc_to_priv(struct gpio_chip *gc)
> +{
> + struct bgpio_chip *bgc = to_bgpio_chip(gc);
> +
> + return container_of(bgc, struct grgpio_priv, bgc);
> +}
> +
> +static int grgpio_to_irq(struct gpio_chip *gc, unsigned offset)
> +{
> + return -ENXIO;
> +}
The gpiolib core already returns -ENXIO if this function is
not assigned so just delete this function and leave that
function pointer as NULL.
> +static int grgpio_probe(struct platform_device *ofdev)
> +{
> + struct device_node *np = ofdev->dev.of_node;
> + struct grgpio_regs __iomem *regs;
Prefer void __iomem *base;
> + struct gpio_chip *gc;
> + struct bgpio_chip *bgc;
> + struct grgpio_priv *priv;
> + struct resource *res;
> + int err;
> + u32 prop;
> +
> + priv = devm_kzalloc(&ofdev->dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + res = platform_get_resource(ofdev, IORESOURCE_MEM, 0);
> + regs = devm_ioremap_resource(&ofdev->dev, res);
> + if (IS_ERR(regs))
> + return PTR_ERR(regs);
> +
> + bgc = &priv->bgc;
> + err = bgpio_init(bgc, &ofdev->dev, 4, ®s->data, ®s->output, NULL,
> + ®s->dir, NULL, BGPIOF_BIG_ENDIAN_BYTE_ORDER);
So I would prefer if you did:
#define GRGPIO_DATA 0x00
#define GRGPIO_OUTPUT 0x04
#define GRGPIO_DIR 0x08
(...)
err = bgpio_init(bgc, &ofdev->dev, 4, base + GRGPIO_DATA, base +
GRGPIO_OUTPUT, NULL,
base + GRGPIO_DIR, NULL, BGPIOF_BIG_ENDIAN_BYTE_ORDER);
> + if (err) {
> + dev_err(&ofdev->dev, "bgpio_init() failed\n");
> + return err;
> + }
> +
> + priv->regs = regs;
> + priv->dev = &ofdev->dev;
> +
> + gc = &bgc->gc;
> + gc->of_node = np;
> + gc->owner = THIS_MODULE;
> + gc->to_irq = grgpio_to_irq;
> + gc->label = np->full_name;
> +
> + err = of_property_read_u32(np, "base", &prop);
> + if (err) {
> + dev_dbg(&ofdev->dev, "No base property: use dynamic base\n");
> + gc->base = -1;
> + } else {
> + gc->base = prop;
> + }
Over my dead body ;-)
(...)
> +static struct of_device_id grgpio_match[] = {
> + {.name = "GAISLER_GPIO"},
> + {.name = "01_01a"},
> + {},
> +};
This is very weird. Especially "01_01a" needs a real good explanation
if it is to be kept.
Alas, I don't really know what the .name field in the of_device_id is for...
Yours,
Linus Walleij
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