Re: [PATCH v5 2/4] misc: Generic on-chip SRAM allocation driver

[Paul Gortmaker]

On Thu, Oct 18, 2012 at 10:27 AM, Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> wrote:
> This driver requests and remaps a memory region as configured in the
> device tree. It serves memory from this region via the genalloc API.
>
> Other drivers can retrieve the genalloc pool from a phandle pointing
> to this drivers' device node in the device tree.
>
> Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> Reviewed-by: Shawn Guo <shawn.guo@xxxxxxxxxx>
> ---
>  Documentation/devicetree/bindings/misc/sram.txt |   17 ++++
>  drivers/misc/Kconfig                            |    9 ++
>  drivers/misc/Makefile                           |    1 +
>  drivers/misc/sram.c                             |  111 +++++++++++++++++++++++
>  4 files changed, 138 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/misc/sram.txt
>  create mode 100644 drivers/misc/sram.c
>
> diff --git a/Documentation/devicetree/bindings/misc/sram.txt b/Documentation/devicetree/bindings/misc/sram.txt
> new file mode 100644
> index 0000000..b64136c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/misc/sram.txt
> @@ -0,0 +1,17 @@
> +Generic on-chip SRAM
> +
> +Simple IO memory regions to be managed by the genalloc API.
> +
> +Required properties:
> +
> +- compatible : sram
> +
> +- reg : SRAM iomem address range
> +
> +Example:
> +
> +sram: sram@5c000000 {
> +       compatible = "sram";
> +       reg = <0x5c000000 0x40000>; /* 256 KiB SRAM at address 0x5c000000 */
> +};
> +
> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index b151b7c..c5bbd00 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -499,6 +499,15 @@ config USB_SWITCH_FSA9480
>           stereo and mono audio, video, microphone and UART data to use
>           a common connector port.
>
> +config SRAM
> +       bool "Generic on-chip SRAM driver"

If it is bool, then why bother with module.h and all the
MODULE_AUTHOR and similar stuff?

> +       depends on HAS_IOMEM
> +       select GENERIC_ALLOCATOR
> +       help
> +         This driver allows to declare a memory region to be managed
> +         by the genalloc API. It is supposed to be used for small
> +         on-chip SRAM areas found on many ARM SoCs.

Probably no need to call out ARM specifically here.  I'm pretty sure
quite a few of the powerpc parts have SRAM too.

> +
>  source "drivers/misc/c2port/Kconfig"
>  source "drivers/misc/eeprom/Kconfig"
>  source "drivers/misc/cb710/Kconfig"
> diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
> index 2129377..d845690 100644
> --- a/drivers/misc/Makefile
> +++ b/drivers/misc/Makefile
> @@ -49,3 +49,4 @@ obj-y                         += carma/
>  obj-$(CONFIG_USB_SWITCH_FSA9480) += fsa9480.o
>  obj-$(CONFIG_ALTERA_STAPL)     +=altera-stapl/
>  obj-$(CONFIG_INTEL_MEI)                += mei/
> +obj-$(CONFIG_SRAM)             += sram.o
> diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
> new file mode 100644
> index 0000000..7a363f2
> --- /dev/null
> +++ b/drivers/misc/sram.c
> @@ -0,0 +1,111 @@
> +/*
> + * Generic on-chip SRAM allocation driver
> + *
> + * Copyright (C) 2012 Philipp Zabel, Pengutronix
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version 2
> + * of the License, or (at your option) any later version.
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
> + * MA 02110-1301, USA.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/io.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/spinlock.h>
> +#include <linux/genalloc.h>
> +
> +struct sram_dev {
> +       struct gen_pool *pool;
> +};

Assuming you don't ever intend adding more to the struct, then:

static struct gen_pool *sram_pool;

instead?  And you'll lose the needless indirections in the
remaining code below, and the kzalloc too (which you
currently leak, btw).  I'd also delete the "/* sentinel */"
comment too, since it is self evident. (The disease has
spread by copying from other drivers I see).

P.
--

> +
> +static int __devinit sram_probe(struct platform_device *pdev)
> +{
> +       void __iomem *virt_base;
> +       struct sram_dev *sram;
> +       struct resource *res;
> +       unsigned long size;
> +       int ret;
> +
> +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +       if (!res)
> +               return -EINVAL;
> +
> +       size = resource_size(res);
> +
> +       virt_base = devm_request_and_ioremap(&pdev->dev, res);
> +       if (!virt_base)
> +               return -EADDRNOTAVAIL;
> +
> +       sram = devm_kzalloc(&pdev->dev, sizeof(*sram), GFP_KERNEL);
> +       if (!sram)
> +               return -ENOMEM;
> +
> +       sram->pool = gen_pool_create(PAGE_SHIFT, -1);
> +       if (!sram->pool)
> +               return -ENOMEM;
> +
> +       ret = gen_pool_add_virt(sram->pool, (unsigned long)virt_base,
> +                               res->start, size, -1);
> +       if (ret < 0) {
> +               gen_pool_destroy(sram->pool);
> +               return ret;
> +       }
> +
> +       platform_set_drvdata(pdev, sram);
> +
> +       dev_dbg(&pdev->dev, "SRAM pool: %ld KiB @ 0x%p\n", size / 1024, virt_base);
> +
> +       return 0;
> +}
> +
> +static int __devexit sram_remove(struct platform_device *pdev)
> +{
> +       struct sram_dev *sram = platform_get_drvdata(pdev);
> +
> +       if (gen_pool_avail(sram->pool) < gen_pool_size(sram->pool))
> +               dev_dbg(&pdev->dev, "removed while SRAM allocated\n");
> +
> +       gen_pool_destroy(sram->pool);
> +
> +       return 0;
> +}
> +
> +#ifdef CONFIG_OF
> +static struct of_device_id sram_dt_ids[] = {
> +       { .compatible = "sram" },
> +       { /* sentinel */ }
> +};
> +#endif
> +
> +static struct platform_driver sram_driver = {
> +       .driver = {
> +               .name = "sram",
> +               .of_match_table = of_match_ptr(sram_dt_ids),
> +       },
> +       .probe = sram_probe,
> +       .remove = __devexit_p(sram_remove),
> +};
> +
> +int __init sram_init(void)
> +{
> +       return platform_driver_register(&sram_driver);
> +}
> +
> +postcore_initcall(sram_init);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Philipp Zabel, Pengutronix");
> +MODULE_DESCRIPTION("Generic SRAM allocator driver");
> --
> 1.7.10.4
>
> --
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