[Skiboot] [PATCH 2/2] platform/mihawk: Tune equalization settings for opencapi

[Andrew Donnellan]

On 31/3/20 8:47 pm, Frederic Barrat wrote:
> The Bittware 250SOC adapter on Mihawk was showing a high count of CRC
> errors on one of the opencapi slots. The PHY team suggested new
> equalization settings to correct the errors.
> 
> All existing adapters have been tested on mihawk to make sure the
> settings are compatible. However, the new settings should not be used
> on platforms other than mihawk.
> 
> The changes specific to mihawk are:
> - Update the tx_ffe_pre_coeff and tx_ffe_post_coeff input parameters
>    used during zcal
> - turn off the tx_ffe_boost parameter through scom
> 
> Signed-off-by: Frederic Barrat <fbarrat at linux.ibm.com>
> Cc: skiboot-stable at lists.ozlabs.org # skiboot-op940.x

I can't validate the specific equalisation settings, so I'll take your 
word that they are indeed correct.

> ---
>   hw/npu2-hw-procedures.c   | 25 ++++++++++++++++++-------
>   include/npu2.h            |  2 ++
>   platforms/astbmc/mihawk.c |  1 +
>   3 files changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/npu2-hw-procedures.c b/hw/npu2-hw-procedures.c
> index 890b25a8..95a0f9dc 100644
> --- a/hw/npu2-hw-procedures.c
> +++ b/hw/npu2-hw-procedures.c
> @@ -78,6 +78,7 @@ static struct npu2_phy_reg NPU2_PHY_TX_ZCAL_DONE	       = {0x3c1, 50, 1};
>   static struct npu2_phy_reg NPU2_PHY_TX_ZCAL_ERROR	       = {0x3c1, 51, 1};
>   static struct npu2_phy_reg NPU2_PHY_TX_ZCAL_N		       = {0x3c3, 48, 9};
>   static struct npu2_phy_reg NPU2_PHY_TX_ZCAL_P		       = {0x3c5, 48, 9};
> +static struct npu2_phy_reg NPU2_PHY_TX_FFE_BOOST_EN	       = {0x34b, 59, 1};
>   static struct npu2_phy_reg NPU2_PHY_TX_PSEG_PRE_EN	       = {0x34d, 51, 5};
>   static struct npu2_phy_reg NPU2_PHY_TX_PSEG_PRE_SELECT	       = {0x34d, 56, 5};
>   static struct npu2_phy_reg NPU2_PHY_TX_NSEG_PRE_EN	       = {0x34f, 51, 5};
> @@ -498,10 +499,11 @@ static uint32_t phy_tx_zcal_wait(struct npu2_dev *ndev)
>   	return PROCEDURE_NEXT;
>   }
>   
> -#define MARGIN_RATIO		(0)
> -#define FFE_PRE_COEFF		(0)
> -#define FFE_POST_COEFF		(0)
>   
> +int ffe_pre_coeff = 0;
> +int ffe_post_coeff = 0;

Is there any way to do this without exposing global variables? (My 
primary objection is that global variables for specific things in 
specific subsystems is ugly and inelegant)

-- 
Andrew Donnellan              OzLabs, ADL Canberra
ajd at linux.ibm.com             IBM Australia Limited