Re: [PATCH v2 2/2] e1000e: ignore factory-default checksum value on TGP platform

[Simon Horman <horms@kernel.org>]

On Mon, Jun 23, 2025 at 06:01:16PM +0200, Jacek Kowalski wrote:
> As described by Vitaly Lifshits:
> 
> > Starting from Tiger Lake, LAN NVM is locked for writes by SW, so the
> > driver cannot perform checksum validation and correction. This means
> > that all NVM images must leave the factory with correct checksum and
> > checksum valid bit set.
> 
> Unfortunately some systems have left the factory with an empty checksum.
> NVM is not modifiable on this platform, hence ignore checksum 0xFFFF on
> Tiger Lake systems to work around this.
> 
> Signed-off-by: Jacek Kowalski <Jacek@jacekk.info>
> Fixes: 4051f68318ca9 ("e1000e: Do not take care about recovery NVM checksum")
> Cc: stable@vger.kernel.org
> ---
> v2: new check to fix yet another checksum issue
>  drivers/net/ethernet/intel/e1000e/defines.h | 1 +
>  drivers/net/ethernet/intel/e1000e/nvm.c     | 5 +++++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/e1000e/defines.h b/drivers/net/ethernet/intel/e1000e/defines.h
> index 8294a7c4f122..01696eb8dace 100644
> --- a/drivers/net/ethernet/intel/e1000e/defines.h
> +++ b/drivers/net/ethernet/intel/e1000e/defines.h
> @@ -637,6 +637,7 @@
>  
>  /* For checksumming, the sum of all words in the NVM should equal 0xBABA. */
>  #define NVM_SUM                    0xBABA
> +#define NVM_SUM_FACTORY_DEFAULT    0xFFFF
>  
>  /* PBA (printed board assembly) number words */
>  #define NVM_PBA_OFFSET_0           8
> diff --git a/drivers/net/ethernet/intel/e1000e/nvm.c b/drivers/net/ethernet/intel/e1000e/nvm.c
> index e609f4df86f4..37cbf9236d84 100644
> --- a/drivers/net/ethernet/intel/e1000e/nvm.c
> +++ b/drivers/net/ethernet/intel/e1000e/nvm.c
> @@ -558,6 +558,11 @@ s32 e1000e_validate_nvm_checksum_generic(struct e1000_hw *hw)
>  		checksum += nvm_data;
>  	}
>  
> +	if (hw->mac.type == e1000_pch_tgp && checksum == (u16)NVM_SUM_FACTORY_DEFAULT) {

I see that a similar cast is applied to NVM_SUM. But why?
If it's not necessary then I would advocate dropping it.

> +		e_dbg("Factory-default NVM Checksum on TGP platform - ignoring\n");
> +		return 0;
> +	}
> +
>  	if (checksum != (u16)NVM_SUM) {
>  		e_dbg("NVM Checksum Invalid\n");
>  		return -E1000_ERR_NVM;
> -- 
> 2.47.2
> 
>