[PATCH 1/2] staging/vc04_services: initialize cache line size properly

[PATCH 1/2] staging/vc04_services: initialize cache line size properly

[Arnd Bergmann]

While debugging another problem I noticed that g_cache_line_size gets set
to sizeof(CACHE_LINE_SIZE), which is sizeof(int) or 4, while presumably
CACHE_LINE_SIZE (e.g. 32) was meant.

This initializes it the way it was meant.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
index 3aeffcb9c87e..b0e9eb6ff73f 100644
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
@@ -78,7 +78,7 @@ struct vchiq_pagelist_info {
 };
 
 static void __iomem *g_regs;
-static unsigned int g_cache_line_size = sizeof(CACHE_LINE_SIZE);
+static unsigned int g_cache_line_size = CACHE_LINE_SIZE;
 static unsigned int g_fragments_size;
 static char *g_fragments_base;
 static char *g_free_fragments;
-- 
2.9.0

[PATCH 2/2] staging/vc04_services: add CONFIG_OF dependency

[Arnd Bergmann]

After several hours of debugging this obviously bogus but elaborate
gcc-7.0.1 warning,

drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c: In function 'vchiq_complete_bulk':
drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c:603:4: error: argument 2 null where non-null expected [-Werror=nonnull]
    memcpy((char *)page_address(pages[0]) +
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     pagelist->offset,
     ~~~~~~~~~~~~~~~~~
     fragments,
     ~~~~~~~~~~
     head_bytes);
     ~~~~~~~~~~~
In file included from include/linux/string.h:18:0,
                 from include/linux/bitmap.h:8,
                 from include/linux/cpumask.h:11,
                 from include/linux/interrupt.h:9,
                 from drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c:37:
arch/arm/include/asm/string.h:16:15: note: in a call to function 'memcpy' declared here
 extern void * memcpy(void *, const void *, __kernel_size_t) __nocapture(2);
               ^~~~~~

I have concluded that gcc was technically right in the first place:

vchiq_complete_bulk is an externally visible function that calls
free_pagelist(), which in turn derives a pointer from the global
g_fragments_base variable.

g_fragments_base is initialized in vchiq_platform_init(), but
we only get there if of_property_read_u32() successfully reads the
cache line size. When CONFIG_OF is disabled, this always fails, and
g_fragments_base is guaranteed to be NULL when vchiq_complete_bulk()
gets called.

This adds a CONFIG_OF Kconfig dependency, which is also technically correct
but nonobvious, and thus seems like a good fit for the warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/staging/vc04_services/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/staging/vc04_services/Kconfig b/drivers/staging/vc04_services/Kconfig
index e61e4ca064a8..74094fff4367 100644
--- a/drivers/staging/vc04_services/Kconfig
+++ b/drivers/staging/vc04_services/Kconfig
@@ -1,6 +1,7 @@
 config BCM2835_VCHIQ
 	tristate "Videocore VCHIQ"
 	depends on HAS_DMA
+	depends on OF
 	depends on RASPBERRYPI_FIRMWARE || (COMPILE_TEST && !RASPBERRYPI_FIRMWARE)
 	default y
 	help
-- 
2.9.0

Re: [PATCH 1/2] staging/vc04_services: initialize cache line size properly

[Michael Zoran]

Hi Arnd,

I submitted a change which is in Linux-next now that makes the whole
CACHE_LINE_SIZE macro meaningless.  It now always reads the size from
the DT and errors out with -ENODEV if the property is missing.

I was going to submit a change to delete the macro completely, just
never got to it.

https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit
/drivers/staging/vc04_services/interface?id=6cf1bf636a067eb308cb3a8322b
9d6b1844a075d

On Wed, 2017-03-01 at 23:50 +0100, Arnd Bergmann wrote:
> While debugging another problem I noticed that g_cache_line_size gets
> set
> to sizeof(CACHE_LINE_SIZE), which is sizeof(int) or 4, while
> presumably
> CACHE_LINE_SIZE (e.g. 32) was meant.
> 
> This initializes it the way it was meant.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c |
> 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git
> a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
> b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
> index 3aeffcb9c87e..b0e9eb6ff73f 100644
> ---
> a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
> +++
> b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c
> @@ -78,7 +78,7 @@ struct vchiq_pagelist_info {
>  };
>  
>  static void __iomem *g_regs;
> -static unsigned int g_cache_line_size = sizeof(CACHE_LINE_SIZE);
> +static unsigned int g_cache_line_size = CACHE_LINE_SIZE;
>  static unsigned int g_fragments_size;
>  static char *g_fragments_base;
>  static char *g_free_fragments;

Re: [PATCH 1/2] staging/vc04_services: initialize cache line size properly

[Greg Kroah-Hartman]

On Wed, Mar 01, 2017 at 05:59:38PM -0800, Michael Zoran wrote:
> Hi Arnd,
> 
> I submitted a change which is in Linux-next now that makes the whole
> CACHE_LINE_SIZE macro meaningless.  It now always reads the size from
> the DT and errors out with -ENODEV if the property is missing.
> 
> I was going to submit a change to delete the macro completely, just
> never got to it.
> 
> https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit
> /drivers/staging/vc04_services/interface?id=6cf1bf636a067eb308cb3a8322b
> 9d6b1844a075d

This should be in 4.11-rc1.

thanks,

greg k-h