Re: [PATCH v9 RESEND 2/4] misc: Generic on-chip SRAM allocation driver

[Andrew Morton <akpm@linux-foundation.org>]

On Wed, 20 Mar 2013 11:52:45 +0100 Philipp Zabel <p.zabel@pengutronix.de> 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.
> It optionally enables the SRAM clock.
> 
> Other drivers can retrieve the genalloc pool from a phandle pointing
> to this drivers' device node in the device tree.
> 
> The allocation granularity is hard-coded to 32 bytes for now,
> to make the SRAM driver useful for the 6502 remoteproc driver.
> There is overhead for bigger SRAMs, where only a much coarser
> allocation granularity is needed: At 32 bytes minimum allocation
> size, a 256 KiB SRAM needs a 1 KiB bitmap to track allocations.
> 
>  Documentation/devicetree/bindings/misc/sram.txt |   16 +++
>  drivers/misc/Kconfig                            |    9 ++
>  drivers/misc/Makefile                           |    1 +
>  drivers/misc/sram.c                             |  121 +++++++++++++++++++++++

drivers/misc/sram.c is a pretty generic-sounding thing.  Is it really
Linux's One True SRAM driver?  How many different sorts of sram devices
do we expect this can be used with?  If I don't use DT?

In other words, perhaps this should have a more specific and accurate
name?

> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -510,6 +510,15 @@ config LATTICE_ECP3_CONFIG
>  
>  	  If unsure, say N.
>  
> ...
>
> +static int 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;

EADDRNOTAVAIL is a networking error.  If your users see this error pop
up on their console they'll start wiggling ethernet cables, wondering
why that didn't fix it.

> +	sram = devm_kzalloc(&pdev->dev, sizeof(*sram), GFP_KERNEL);
> +	if (!sram)
> +		return -ENOMEM;
> +
> +	sram->clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(sram->clk))
> +		sram->clk = NULL;
> +	else
> +		clk_prepare_enable(sram->clk);
> +
> +	sram->pool = devm_gen_pool_create(&pdev->dev, ilog2(SRAM_GRANULARITY), -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;
> +}
>
> ...
>
> +int __init sram_init(void)
> +{
> +	return platform_driver_register(&sram_driver);
> +}
> +
> +postcore_initcall(sram_init);

Why is it postcore_initcall()?


Fixlets:

From: Andrew Morton <akpm@linux-foundation.org>
Subject: misc-generic-on-chip-sram-allocation-driver-fix

fix Kconfig text, make sram_init static

Cc: Dong Aisheng <dong.aisheng@linaro.org>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Huang Shijie <shijie8@gmail.com>
Cc: Javier Martin <javier.martin@vista-silicon.com>
Cc: Matt Porter <mporter@ti.com>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Rob Herring <rob.herring@calxeda.com>
Cc: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/misc/Kconfig |    6 +++---
 drivers/misc/sram.c  |    2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff -puN Documentation/devicetree/bindings/misc/sram.txt~misc-generic-on-chip-sram-allocation-driver-fix Documentation/devicetree/bindings/misc/sram.txt
diff -puN drivers/misc/Kconfig~misc-generic-on-chip-sram-allocation-driver-fix drivers/misc/Kconfig
--- a/drivers/misc/Kconfig~misc-generic-on-chip-sram-allocation-driver-fix
+++ a/drivers/misc/Kconfig
@@ -523,9 +523,9 @@ config SRAM
 	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 SoCs.
+	  This driver allows you 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 SoCs.
 
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
diff -puN drivers/misc/Makefile~misc-generic-on-chip-sram-allocation-driver-fix drivers/misc/Makefile
diff -puN drivers/misc/sram.c~misc-generic-on-chip-sram-allocation-driver-fix drivers/misc/sram.c
--- a/drivers/misc/sram.c~misc-generic-on-chip-sram-allocation-driver-fix
+++ a/drivers/misc/sram.c
@@ -113,7 +113,7 @@ static struct platform_driver sram_drive
 	.remove = sram_remove,
 };
 
-int __init sram_init(void)
+static int __init sram_init(void)
 {
 	return platform_driver_register(&sram_driver);
 }
_