[U-Boot] [PATCH] arm: socfpga: Fix cache configuration

[Marek Vasut <marex@denx.de>]

On Thursday, September 17, 2015 at 05:30:29 PM, Stefan Roese wrote:

Hi!

> By not defining CONFIG_SYS_ARM_CACHE_WRITEALLOC, the WRITEBACK cache
> policy is selected. This leads to much better performance on the SoCFPGA.
> A quick network test shows this:
> 
> Without this patch:
> => tftp 100000 big-40mb
> Speed: 1000, full duplex
> Using dwmac.ff702000 device
> TFTP from server 192.168.1.54; our IP address is 192.168.1.252
> Filename 'big-40mb'.
> Load address: 0x100000
> Loading: #################################################################
>          #################################################################
>          #################################################################
>          #################################################################
>          ##########################
>          2.5 MiB/s
> 
> With this patch:
> => tftp 100000 big-40mb
> Speed: 1000, full duplex
> Using dwmac.ff702000 device
> TFTP from server 192.168.1.54; our IP address is 192.168.1.252
> Filename 'big-40mb'.
> Load address: 0x100000
> Loading: #################################################################
>          #################################################################
>          #################################################################
>          #################################################################
>          ##########################
>          7.6 MiB/s
> 
> A performance improvement of factor ~3.
> 
> Signed-off-by: Stefan Roese <sr@denx.de>
> Cc: Dinh Nguyen <dinguyen@opensource.altera.com>
> Cc: Chin Liang See <clsee@altera.com>
> Cc: Pavel Machek <pavel@denx.de>
> Cc: Marek Vasut <marex@denx.de>
> ---
>  include/configs/socfpga_common.h | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/include/configs/socfpga_common.h
> b/include/configs/socfpga_common.h index 38ae763..a2811ba 100644
> --- a/include/configs/socfpga_common.h
> +++ b/include/configs/socfpga_common.h
> @@ -73,7 +73,6 @@
>  /*
>   * Cache
>   */
> -#define CONFIG_SYS_ARM_CACHE_WRITEALLOC
>  #define CONFIG_SYS_CACHELINE_SIZE 32
>  #define CONFIG_SYS_L2_PL310
>  #define CONFIG_SYS_PL310_BASE		SOCFPGA_MPUL2_ADDRESS

I hate to say it, but I am running into issues with this patch :-(

I use a standard USB stick here and with this patch, I am getting the following
failure (with enabled and disabled cache):

=> usb reset
resetting USB...
USB0:   Core Release: 2.93a
scanning bus 0 for devices... unable to get descriptor, error 0
usb_new_device: Cannot read configuration, skipping device 058f:6387
1 USB Device(s) found
       scanning usb for storage devices... 0 Storage Device(s) found
=> dcache off
=> usb reset 
resetting USB...
USB0:   Core Release: 2.93a
scanning bus 0 for devices... 2 USB Device(s) found
       scanning usb for storage devices... 1 Storage Device(s) found

If I revert this patch, my USB stick works as well.

I am also aware that Stefan mentions that without this patch, cache is not 
enabled at all. On the other hand, I cannot find any obviously faulty behavior
in the dwc2 driver, it does flush_dcache_range()/invalidate_dcache_range() in
the right places.

Any ideas please ?

Best regards,
Marek Vasut