[Skiboot] [PATCH v2 1/2] opal/xscom: Move the delay inside xscom_reset() function.

[Nicholas Piggin]

On Fri, 08 Dec 2017 16:19:35 +0530
Mahesh J Salgaonkar <mahesh at linux.vnet.ibm.com> wrote:

> From: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
> 
> So caller of xscom_reset() does not have to bother about adding a delay
> separately. Instead caller can control whether to add a delay or not using
> second argument to xscom_reset().
> 
> Signed-off-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>

Reviewed-by: Nicholas Piggin <npiggin at gmail.com>

> ---
> Changes in V2:
> - Add a bool argument to xscom_reset() to give the control to caller whether to
>   delay is required or not after reset.
> ---
>  hw/xscom.c |   39 +++++++++++++++++++++------------------
>  1 file changed, 21 insertions(+), 18 deletions(-)
> 
> diff --git a/hw/xscom.c b/hw/xscom.c
> index 5b3bd88..d98f5ef 100644
> --- a/hw/xscom.c
> +++ b/hw/xscom.c
> @@ -92,10 +92,11 @@ static uint64_t xscom_wait_done(void)
>  	return mfspr(SPR_HMER);
>  }
>  
> -static void xscom_reset(uint32_t gcid)
> +static void xscom_reset(uint32_t gcid, bool need_delay)
>  {
>  	u64 hmer;
>  	uint32_t recv_status_reg, log_reg, err_reg;
> +	struct timespec ts;
>  
>  	/* Clear errors in HMER */
>  	mtspr(SPR_HMER, HMER_CLR_MASK);
> @@ -126,6 +127,21 @@ static void xscom_reset(uint32_t gcid)
>  	hmer = xscom_wait_done();
>  	if (hmer & SPR_HMER_XSCOM_FAIL)
>  		goto fail;
> +
> +	if (need_delay) {
> +		/*
> +		 * Its observed that sometimes immediate retry of
> +		 * XSCOM operation returns wrong data. Adding a
> +		 * delay for XSCOM reset to be effective. Delay of
> +		 * 10 ms is found to be working fine experimentally.
> +		 * FIXME: Replace 10ms delay by exact delay needed
> +		 * or other alternate method to confirm XSCOM reset
> +		 * completion, after checking from HW folks.
> +		 */
> +		ts.tv_sec = 0;
> +		ts.tv_nsec = 10 * 1000;
> +		nanosleep_nopoll(&ts, NULL);
> +	}
>  	return;
>   fail:
>  	/* Fatal error resetting XSCOM */
> @@ -140,7 +156,6 @@ static void xscom_reset(uint32_t gcid)
>  static int64_t xscom_handle_error(uint64_t hmer, uint32_t gcid, uint32_t pcb_addr,
>  			      bool is_write, int64_t retries)
>  {
> -	struct timespec ts;
>  	unsigned int stat = GETFIELD(SPR_HMER_XSCOM_STATUS, hmer);
>  	int64_t rc = OPAL_HARDWARE;
>  
> @@ -158,20 +173,8 @@ static int64_t xscom_handle_error(uint64_t hmer, uint32_t gcid, uint32_t pcb_add
>  			prlog(PR_NOTICE, "XSCOM: Busy even after %d retries, "
>  				"resetting XSCOM now. Total retries  = %lld\n",
>  				XSCOM_BUSY_RESET_THRESHOLD, retries);
> -			xscom_reset(gcid);
> -
> -			/*
> -			 * Its observed that sometimes immediate retry of
> -			 * XSCOM operation returns wrong data. Adding a
> -			 * delay for XSCOM reset to be effective. Delay of
> -			 * 10 ms is found to be working fine experimentally.
> -			 * FIXME: Replace 10ms delay by exact delay needed
> -			 * or other alternate method to confirm XSCOM reset
> -			 * completion, after checking from HW folks.
> -			 */
> -			ts.tv_sec = 0;
> -			ts.tv_nsec = 10 * 1000;
> -			nanosleep_nopoll(&ts, NULL);
> +			xscom_reset(gcid, true);
> +
>  		}
>  
>  		/* Log error if we have retried enough and its still busy */
> @@ -183,7 +186,7 @@ static int64_t xscom_handle_error(uint64_t hmer, uint32_t gcid, uint32_t pcb_add
>  		return OPAL_XSCOM_BUSY;
>  
>  	case 2: /* CPU is asleep, reset XSCOM engine and return */
> -		xscom_reset(gcid);
> +		xscom_reset(gcid, false);
>  		return OPAL_XSCOM_CHIPLET_OFF;
>  	case 3: /* Partial good */
>  		rc = OPAL_XSCOM_PARTIAL_GOOD;
> @@ -208,7 +211,7 @@ static int64_t xscom_handle_error(uint64_t hmer, uint32_t gcid, uint32_t pcb_add
>  		is_write ? "write" : "read", gcid, pcb_addr, stat);
>  
>  	/* We need to reset the XSCOM or we'll hang on the next access */
> -	xscom_reset(gcid);
> +	xscom_reset(gcid, false);
>  
>  	/* Non recovered ... just fail */
>  	return rc;
> 
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