[coreboot] [PATCH] nb/intel/nehalem/raminit.c: Add timeouts when waiting for heci.

[Timothy Pearson]

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On 03/27/2017 03:05 PM, Denis 'GNUtoo' Carikli wrote:
> Since until now, the code running on the management engine is:
> - Signed by its manufacturer
> - Proprietary software, without corresponding source code
> It can desirable to run the least ammount possible of such
> code, which is what me_cleaner[1] enables.
> 
> It does it by removing partitions of the management engine
> firmwares, however when doing so, the HECI interface might
> not be present anymore.
> 
> So it is desirable not to have the RAM initialisation code
> wait forever for the HECI interface to appear.
> 
> [1] https://github.com/corna/me_cleaner/
> 
> Change-Id: Iebafa353ecd8875395d6c3a986da6082772e2e18
> Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo at no-log.org>
> ---
>  src/northbridge/intel/nehalem/raminit.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/src/northbridge/intel/nehalem/raminit.c b/src/northbridge/intel/nehalem/raminit.c
> index 122b8ac7cf..27065d139e 100644
> --- a/src/northbridge/intel/nehalem/raminit.c
> +++ b/src/northbridge/intel/nehalem/raminit.c
> @@ -1753,23 +1753,27 @@ static const struct ram_training *get_cached_training(void)
>  }
>  #endif
>  
> -/* FIXME: add timeout.  */
>  static void wait_heci_ready(void)
>  {
> -	while (!(read32(DEFAULT_HECIBAR + 0xc) & 8));	// = 0x8000000c
> +	int i = 1000*1000;
> +
> +	while (i-- && !(read32(DEFAULT_HECIBAR + 0xc) & 8)) /* = 0x8000000c */
> +		udelay(1);
>  	write32((DEFAULT_HECIBAR + 0x4),
>  		(read32(DEFAULT_HECIBAR + 0x4) & ~0x10) | 0xc);
>  }
>  
> -/* FIXME: add timeout.  */
>  static void wait_heci_cb_avail(int len)
>  {
> +	int i = 1000*1000;
> +
>  	union {
>  		struct mei_csr csr;
>  		u32 raw;
>  	} csr;
>  
> -	while (!(read32(DEFAULT_HECIBAR + 0xc) & 8));
> +	while (i-- && !(read32(DEFAULT_HECIBAR + 0xc) & 8))
> +		udelay(1);
>  
>  	do
>  		csr.raw = read32(DEFAULT_HECIBAR + 0x4);

In general static timeouts are not a good idea.  Is there a reliable way
for coreboot to determine if the ME image has been "cleaned" (i.e. can
it parse the ME descriptor and not even search for the HECI interface if
the ME size is less than a certain value?)

- -- 
Timothy Pearson
Raptor Engineering
+1 (415) 727-8645 (direct line)
+1 (512) 690-0200 (switchboard)
https://www.raptorengineering.com
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