[PATCH] ARM: mm: fix support for HW coherent systems in PL310 cache

[Gregory CLEMENT]

Hi Russell,

please ignore this one it is the wrong version.

Sorry for the noise

Gregory


On 11/08/2015 19:03, Gregory CLEMENT wrote:
> From: Nadav Haklai <nadavh at marvell.com>
> 
> When a PL310 cache is used in a system that provides hardware
> coherency, the entire outer cache operations are useless, and can be
> skipped.  Moreover, on some systems, it is harmful as it causes
> deadlocks between the Marvell coherency mechanism, the Marvell PCIe
> controller and the Cortex-A9.
> 
> This commit extends a previous commit:
> 98ea2dba65932ffc456b6d7b11b8a0624e2f7b95 which added the io-coherent
> support for the PL310 cache by also disabling the outer cache flush
> range operation.
> 
> In the current kernel implementation, the outer cache flush range
> operation is triggered by the dma_alloc function.
> This operation can be take place during runtime and in some
> circumstances may lead to the PCIe/PL310 deadlock on Armada 375/38x
> SoCs.
> 
> Signed-off-by: Nadav Haklai <nadavh at marvell.com>
> Reviewed-by: Ofer Heifetz <oferh at marvell.com>
> Signed-off-by: Gregory CLEMENT <gregory.clement at free-electrons.com>
> ---
>  arch/arm/mm/cache-l2x0.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm/mm/cache-l2x0.c b/arch/arm/mm/cache-l2x0.c
> index 71b3d3309024..5c3148675597 100644
> --- a/arch/arm/mm/cache-l2x0.c
> +++ b/arch/arm/mm/cache-l2x0.c
> @@ -1266,9 +1266,9 @@ static const struct l2c_init_data of_l2c310_data __initconst = {
>  };
>  
>  /*
> - * This is a variant of the of_l2c310_data with .sync set to
> - * NULL. Outer sync operations are not needed when the system is I/O
> - * coherent, and potentially harmful in certain situations (PCIe/PL310
> + * This is a variant of the of_l2c310_data with .sync and .flush_range set to
> + * NULL. Outer sync and flush range operations are not needed when the system
> + * is I/O coherent, and potentially harmful in certain situations (PCIe/PL310
>   * deadlock on Armada 375/38x due to hardware I/O coherency). The
>   * other operations are kept because they are infrequent (therefore do
>   * not cause the deadlock in practice) and needed for secondary CPU
> @@ -1287,7 +1287,6 @@ static const struct l2c_init_data of_l2c310_coherent_data __initconst = {
>  	.outer_cache = {
>  		.inv_range   = l2c210_inv_range,
>  		.clean_range = l2c210_clean_range,
> -		.flush_range = l2c210_flush_range,
>  		.flush_all   = l2c210_flush_all,
>  		.disable     = l2c310_disable,
>  		.resume      = l2c310_resume,
> 


-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com