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Message-ID: <CACh+v5MPTx6nwVj1s3krntJqQ6DMTQ2hQ93Hc+rRNAuFa9+qPw@mail.gmail.com>
Date: Fri, 21 Feb 2014 17:22:06 +0100
From: Jean-Jacques Hiblot <jjhiblot@...phandler.com>
To: "Strashko, Grygorii" <grygorii.strashko@...com>
Cc: Jean-Jacques Hiblot <jjhiblot@...phandler.com>,
"grant.likely@...aro.org" <grant.likely@...aro.org>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"robh+dt@...nel.org" <robh+dt@...nel.org>,
"thierry.reding@...il.com" <thierry.reding@...il.com>,
"gregory.clement@...e-electrons.com"
<gregory.clement@...e-electrons.com>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"Shilimkar, Santosh" <santosh.shilimkar@...com>
Subject: Re: [PATCH v2] dt: platform driver: Fill the resources before probe
and defer if needed
Hi Grygorii,
2014-02-21 16:37 GMT+01:00 Strashko, Grygorii <grygorii.strashko@...com>:
> Hi Jean-Jacques,
>
> Sorry for top posting.
>
> As I know, there have been several attempts to solve the same problem already:)
> [1] https://lkml.org/lkml/2013/9/18/216
> [2] https://lkml.org/lkml/2013/11/22/520
> [3] https://lkml.org/lkml/2014/1/8/240
>
> There are some questions related to your approach:
> 1) How to distinguish between cases "IRQ domain not ready" and "wrong IRQ data in DT" or other IRQ parsing errors?
> Otherwise, Driver's probe will be deffered wrongly and forever,
> Thierry Reding has tried to solve this in [1].
This approach doesn't really care about the cause of the problem. I'm
of the opinion that never-ending deferred probing is not a big issue,
being not triggered so often after start-up (only when a new device is
probed). But if we need to make it right, then we would have to change
a bit the API of irq_create_of_mapping() and irq_of_parse_and_map()
(or maybe duplicate this one to keep the patch small) to return a real
error code instead a simple 0. Then would should be able to
distinguish the different error causes.
>
> 2) How will be handled driver reloading situation?
> The worst case (sparse IRQ enabled):
> - remove driver A
> - remove driver B (irq-controller)
> - load driver B <--- different set of Linux IRQ numbers can be assigned
> - load driver A <--- oops. IRQ resources table contains invalid data
>
It's not handled in the current implementation. But if all interrupts
entries are re-parsed (see my comment for Grant), it should be all
right.
Another problem would appear if the DT is dynamically updated and the
number of resource is changed. In the 1st version of the patch, this
was handled but it made the function more expensive.
Jean-Jacques
>
>
> Best regards,
> Grygorii Strashko
>
> =============================================
>
> The goal of this patch is to allow drivers to be probed even if at the time of
> the DT parsing some of their ressources are not available yet.
>
> In the current situation, the resource of a platform device are filled from the
> DT at the time the device is created (of_device_alloc()). The drawbackof this
> is that a device sitting close to the top of the DT (ahb for example) but
> depending on ressources that are initialized later (IRQ domain dynamically
> created for example) will fail to probe because the ressources don't exist
> at this time.
>
> This patch fills the resource structure only before the device is probed and
> will defer the probe if the resource are not available yet.
>
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@...phandler.com>
> Reviewed-by: Gregory CLEMENT <gregory.clement@...e-electrons.com>
> ---
>
> Hi Grant,
>
> I reworked the patch as you proposed. To keep the overhead minimum, nirq and
> nreg are computed only the first time.
> In this implementation, only the missing IRQ ressources are re-tried for. It could
> easily be changed to re-parse all the IRQs though (replace if (!res->flags)
> with if ((!res->flags) || (res->flags & IORESOURCE_IRQ)).
>
> drivers/base/platform.c | 5 +++
> drivers/of/platform.c | 100 +++++++++++++++++++++++++++++++++-----------
> include/linux/of_platform.h | 10 +++++
> 3 files changed, 90 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index bc78848..cee9b8d 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -481,6 +481,10 @@ static int platform_drv_probe(struct device *_dev)
> struct platform_device *dev = to_platform_device(_dev);
> int ret;
>
> + ret = of_platform_device_prepare(dev);
> + if (ret)
> + goto error;
> +
> if (ACPI_HANDLE(_dev))
> acpi_dev_pm_attach(_dev, true);
>
> @@ -488,6 +492,7 @@ static int platform_drv_probe(struct device *_dev)
> if (ret && ACPI_HANDLE(_dev))
> acpi_dev_pm_detach(_dev, true);
>
> +error:
> if (drv->prevent_deferred_probe && ret == -EPROBE_DEFER) {
> dev_warn(_dev, "probe deferral not supported\n");
> ret = -ENXIO;
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index 404d1da..a4e2602 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -141,36 +141,11 @@ struct platform_device *of_device_alloc(struct device_node *np,
> struct device *parent)
> {
> struct platform_device *dev;
> - int rc, i, num_reg = 0, num_irq;
> - struct resource *res, temp_res;
>
> dev = platform_device_alloc("", -1);
> if (!dev)
> return NULL;
>
> - /* count the io and irq resources */
> - if (of_can_translate_address(np))
> - while (of_address_to_resource(np, num_reg, &temp_res) == 0)
> - num_reg++;
> - num_irq = of_irq_count(np);
> -
> - /* Populate the resource table */
> - if (num_irq || num_reg) {
> - res = kzalloc(sizeof(*res) * (num_irq + num_reg), GFP_KERNEL);
> - if (!res) {
> - platform_device_put(dev);
> - return NULL;
> - }
> -
> - dev->num_resources = num_reg + num_irq;
> - dev->resource = res;
> - for (i = 0; i < num_reg; i++, res++) {
> - rc = of_address_to_resource(np, i, res);
> - WARN_ON(rc);
> - }
> - WARN_ON(of_irq_to_resource_table(np, res, num_irq) != num_irq);
> - }
> -
> dev->dev.of_node = of_node_get(np);
> #if defined(CONFIG_MICROBLAZE)
> dev->dev.dma_mask = &dev->archdata.dma_mask;
> @@ -233,6 +208,81 @@ static struct platform_device *of_platform_device_create_pdata(
> return dev;
> }
>
> +static int of_reg_count(struct device_node *np)
> +{
> + int nreg = 0;
> + if (of_can_translate_address(np)) {
> + struct resource temp_res;
> + while (of_address_to_resource(np, nreg, &temp_res) == 0)
> + nreg++;
> + }
> + return nreg;
> +}
> +
> +int of_platform_device_prepare(struct platform_device *dev)
> +{
> + struct device_node *np;
> + int i, irq_index;
> + struct resource *res;
> +
> + /*
> + * This function applies only devices described in the DT.
> + * Other platform devices have their ressources already populated.
> + */
> + np = dev->dev.of_node;
> + if (!np)
> + return 0;
> +
> + /* Populate the resource table */
> + if (!dev->resource) {
> + int rc, nreg = 0, nirq;
> + /* count the io and irq resources */
> + nreg = of_reg_count(np);
> + nirq = of_irq_count(np);
> +
> + if (!nirq && !nreg)
> + return 0;
> +
> + res = kzalloc(sizeof(*res) * (nirq + nreg), GFP_KERNEL);
> + if (!res)
> + return -ENOMEM;
> +
> + dev->resource = res;
> + dev->num_resources = nreg + nirq;
> +
> + for (i = 0; i < nreg; i++, res++) {
> + rc = of_address_to_resource(np, i, res);
> + if (WARN_ON(rc)) {
> + /* THIS IS BAD; don't try to defer probing */
> + dev->num_resources = 0;
> + dev->resource = NULL;
> + kfree(res);
> + return rc;
> + }
> + }
> +
> + if (!rc && of_irq_to_resource_table(np, res, nirq) != nirq) {
> + /* IRQ controller is yet available. defer probing */
> + return -EPROBE_DEFER;
> + }
> +
> + return 0;
> + }
> +
> + /* See which IRQ resources need to be redone */
> + irq_index = 0;
> + for (i = 0, res = dev->resource; i < dev->num_resources; i++, res++) {
> + if (!res->flags) {
> + if (!of_irq_to_resource(np, irq_index, res))
> + return -EPROBE_DEFER;
> + irq_index++;
> + } else if (res->flags & IORESOURCE_IRQ)
> + irq_index++;
> + }
> + return 0;
> +}
> +EXPORT_SYMBOL(of_platform_device_prepare);
> +
> /**
> * of_platform_device_create - Alloc, initialize and register an of_device
> * @np: pointer to node to create device for
> diff --git a/include/linux/of_platform.h b/include/linux/of_platform.h
> index 05cb4a9..4e487ff 100644
> --- a/include/linux/of_platform.h
> +++ b/include/linux/of_platform.h
> @@ -53,6 +53,16 @@ struct of_dev_auxdata {
>
> extern const struct of_device_id of_default_bus_match_table[];
>
> +/* Populate the resource for a platform device */
> +#ifdef CONFIG_OF
> +int of_platform_device_prepare(struct platform_device *dev);
> +#else
> +static inline int of_platform_device_prepare(
> + struct platform_device *dev)
> +{
> + return 0;
> +}
> +#endif
> /* Platform drivers register/unregister */
> extern struct platform_device *of_device_alloc(struct device_node *np,
> const char *bus_id,
> --
> 1.9.0
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
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