diff mbox

[5/5] misc: sram: add Atmel securam support

Message ID 20160831161108.8780-6-alexandre.belloni@free-electrons.com (mailing list archive)
State New, archived
Headers show

Commit Message

Alexandre Belloni Aug. 31, 2016, 4:11 p.m. UTC 
The Atmel secure SRAM is connected to a security module and may be erased
automatically under certain conditions. For that reason, it is necessary to
wait for the security module to flag that SRAM accesses are allowed before
accessing it.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
---
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
 drivers/misc/sram.c | 52 +++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 45 insertions(+), 7 deletions(-)

Comments

Philipp Zabel Aug. 31, 2016, 4:45 p.m. UTC | #1 
Hi Alexandre,

Am Mittwoch, den 31.08.2016, 18:11 +0200 schrieb Alexandre Belloni:
> The Atmel secure SRAM is connected to a security module and may be erased
> automatically under certain conditions. For that reason, it is necessary to
> wait for the security module to flag that SRAM accesses are allowed before
> accessing it.
> 
> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> ---
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Philipp Zabel <p.zabel@pengutronix.de>
> Cc: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
>  drivers/misc/sram.c | 52 +++++++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 45 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
> index f84b53d6ce50..8d411c64d07f 100644
> --- a/drivers/misc/sram.c
> +++ b/drivers/misc/sram.c
> @@ -19,12 +19,16 @@
>   */
>  
>  #include <linux/clk.h>
> +#include <linux/delay.h>
>  #include <linux/genalloc.h>
>  #include <linux/io.h>
>  #include <linux/list_sort.h>
>  #include <linux/of_address.h>
>  #include <linux/platform_device.h>
> +#include <linux/regmap.h>
>  #include <linux/slab.h>
> +#include <linux/mfd/syscon.h>
> +#include <soc/at91/atmel-secumod.h>
>  
>  #define SRAM_GRANULARITY	32
>  
> @@ -334,12 +338,43 @@ static int sram_reserve_regions(struct sram_dev *sram, struct resource *res)
>  	return ret;
>  }
>  
> +static int atmel_securam_wait(void)
> +{
> +	struct regmap *regmap;
> +	unsigned long timeout = jiffies + HZ;

Can this really take up to a second?

> +	u32 val;
> +
> +	regmap = syscon_regmap_lookup_by_compatible("atmel,sama5d2-secumod");
> +	if (IS_ERR(regmap))
> +		return -ENODEV;
> +
> +	regmap_read(regmap, AT91_SECUMOD_RAMRDY, &val);
> +	while (!(val & AT91_SECUMOD_RAMRDY_READY) &&
> +	       time_before(jiffies, timeout)) {
> +		mdelay(10);
> +		regmap_read(regmap, AT91_SECUMOD_RAMRDY, &val);
> +	}
> +	if (!time_before(jiffies, timeout))
> +		return -ETIMEDOUT;
> +
> +	return 0;

Could you use regmap_read_poll_timeout here?

> +}
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id sram_dt_ids[] = {
> +	{ .compatible = "mmio-sram" },
> +	{ .compatible = "atmel,sama5d2-securam", .data = atmel_securam_wait },
> +	{}
> +};
> +#endif
> +
>  static int sram_probe(struct platform_device *pdev)
>  {
>  	struct sram_dev *sram;
>  	struct resource *res;
>  	size_t size;
>  	int ret;
> +	const struct of_device_id *match;
>  
>  	sram = devm_kzalloc(&pdev->dev, sizeof(*sram), GFP_KERNEL);
>  	if (!sram)
> @@ -384,6 +419,16 @@ static int sram_probe(struct platform_device *pdev)
>  
>  	platform_set_drvdata(pdev, sram);
>  
> +	match = of_match_node(sram_dt_ids, pdev->dev.of_node);
> +	if (match->data) {

And of_device_get_match_data here?

> +		int (*init_func)(void);
> +
> +		init_func = match->data;
> +		ret = init_func();
> +		if (ret)
> +			return ret;
> +	}
> +
>  	dev_dbg(sram->dev, "SRAM pool: %zu KiB @ 0x%p\n",
>  		gen_pool_size(sram->pool) / 1024, sram->virt_base);
>  
> @@ -405,13 +450,6 @@ static int sram_remove(struct platform_device *pdev)
>  	return 0;
>  }
>  
> -#ifdef CONFIG_OF
> -static const struct of_device_id sram_dt_ids[] = {
> -	{ .compatible = "mmio-sram" },
> -	{}
> -};
> -#endif
> -
>  static struct platform_driver sram_driver = {
>  	.driver = {
>  		.name = "sram",

regards
Philipp
Alexandre Belloni Aug. 31, 2016, 5:04 p.m. UTC | #2 
On 31/08/2016 at 18:45:37 +0200, Philipp Zabel wrote :
> Hi Alexandre,
> 
> Am Mittwoch, den 31.08.2016, 18:11 +0200 schrieb Alexandre Belloni:
> > The Atmel secure SRAM is connected to a security module and may be erased
> > automatically under certain conditions. For that reason, it is necessary to
> > wait for the security module to flag that SRAM accesses are allowed before
> > accessing it.
> > 
> > Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
> > ---
> > Cc: Arnd Bergmann <arnd@arndb.de>
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: Philipp Zabel <p.zabel@pengutronix.de>
> > Cc: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
> >  drivers/misc/sram.c | 52 +++++++++++++++++++++++++++++++++++++++++++++-------
> >  1 file changed, 45 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
> > index f84b53d6ce50..8d411c64d07f 100644
> > --- a/drivers/misc/sram.c
> > +++ b/drivers/misc/sram.c
> > @@ -19,12 +19,16 @@
> >   */
> >  
> >  #include <linux/clk.h>
> > +#include <linux/delay.h>
> >  #include <linux/genalloc.h>
> >  #include <linux/io.h>
> >  #include <linux/list_sort.h>
> >  #include <linux/of_address.h>
> >  #include <linux/platform_device.h>
> > +#include <linux/regmap.h>
> >  #include <linux/slab.h>
> > +#include <linux/mfd/syscon.h>
> > +#include <soc/at91/atmel-secumod.h>
> >  
> >  #define SRAM_GRANULARITY	32
> >  
> > @@ -334,12 +338,43 @@ static int sram_reserve_regions(struct sram_dev *sram, struct resource *res)
> >  	return ret;
> >  }
> >  
> > +static int atmel_securam_wait(void)
> > +{
> > +	struct regmap *regmap;
> > +	unsigned long timeout = jiffies + HZ;
> 
> Can this really take up to a second?
> 

Well, probably not but it can take some time. My understanding is that
it can take up to almost half a second (4096 bytes at 8kHz). But quite
frankly, by the time linux is starting, the delay has probably already
expired so the while loop is unlikely to run.
diff mbox

Patch

diff --git a/drivers/misc/sram.c b/drivers/misc/sram.c
index f84b53d6ce50..8d411c64d07f 100644
--- a/drivers/misc/sram.c
+++ b/drivers/misc/sram.c
@@ -19,12 +19,16 @@ 
  */
 
 #include <linux/clk.h>
+#include <linux/delay.h>
 #include <linux/genalloc.h>
 #include <linux/io.h>
 #include <linux/list_sort.h>
 #include <linux/of_address.h>
 #include <linux/platform_device.h>
+#include <linux/regmap.h>
 #include <linux/slab.h>
+#include <linux/mfd/syscon.h>
+#include <soc/at91/atmel-secumod.h>
 
 #define SRAM_GRANULARITY	32
 
@@ -334,12 +338,43 @@  static int sram_reserve_regions(struct sram_dev *sram, struct resource *res)
 	return ret;
 }
 
+static int atmel_securam_wait(void)
+{
+	struct regmap *regmap;
+	unsigned long timeout = jiffies + HZ;
+	u32 val;
+
+	regmap = syscon_regmap_lookup_by_compatible("atmel,sama5d2-secumod");
+	if (IS_ERR(regmap))
+		return -ENODEV;
+
+	regmap_read(regmap, AT91_SECUMOD_RAMRDY, &val);
+	while (!(val & AT91_SECUMOD_RAMRDY_READY) &&
+	       time_before(jiffies, timeout)) {
+		mdelay(10);
+		regmap_read(regmap, AT91_SECUMOD_RAMRDY, &val);
+	}
+	if (!time_before(jiffies, timeout))
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id sram_dt_ids[] = {
+	{ .compatible = "mmio-sram" },
+	{ .compatible = "atmel,sama5d2-securam", .data = atmel_securam_wait },
+	{}
+};
+#endif
+
 static int sram_probe(struct platform_device *pdev)
 {
 	struct sram_dev *sram;
 	struct resource *res;
 	size_t size;
 	int ret;
+	const struct of_device_id *match;
 
 	sram = devm_kzalloc(&pdev->dev, sizeof(*sram), GFP_KERNEL);
 	if (!sram)
@@ -384,6 +419,16 @@  static int sram_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, sram);
 
+	match = of_match_node(sram_dt_ids, pdev->dev.of_node);
+	if (match->data) {
+		int (*init_func)(void);
+
+		init_func = match->data;
+		ret = init_func();
+		if (ret)
+			return ret;
+	}
+
 	dev_dbg(sram->dev, "SRAM pool: %zu KiB @ 0x%p\n",
 		gen_pool_size(sram->pool) / 1024, sram->virt_base);
 
@@ -405,13 +450,6 @@  static int sram_remove(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_OF
-static const struct of_device_id sram_dt_ids[] = {
-	{ .compatible = "mmio-sram" },
-	{}
-};
-#endif
-
 static struct platform_driver sram_driver = {
 	.driver = {
 		.name = "sram",