[Skiboot] [PATCH 2/2] FSP: Introduce busy flag in fsp_fetch_data

[Benjamin Herrenschmidt]

On Wed, 2015-03-11 at 18:07 +0530, Vasant Hegde wrote:
> Use busy flag to avoid multiple processors trying to fetch
> at the same time and colliding on the TCE space.
> 
> With this patch we don't hold fsp_fetch_lock before entering
> opal_run_pollers. Fixes "Running pollers with lock held" issue
> as well.
> 
> Signed-off-by: Vasant Hegde <hegdevasant at linux.vnet.ibm.com>
> ---
> Ben,
>   If you are fine with this, I will fix capp_lid_download() as well.

Give it a try and let's see the result

> -Vasant
> 
>  hw/fsp/fsp.c |   43 +++++++++++++++++++++++++++++++++----------
>  1 file changed, 33 insertions(+), 10 deletions(-)
> 
> diff --git a/hw/fsp/fsp.c b/hw/fsp/fsp.c
> index fdf175a..0ab4a56 100644
> --- a/hw/fsp/fsp.c
> +++ b/hw/fsp/fsp.c
> @@ -2142,14 +2142,13 @@ uint32_t fsp_adjust_lid_side(uint32_t lid_no)
>  	return lid_no;
>  }
>  
> -int fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
> -		   uint32_t offset, void *buffer, size_t *length)
> +static int __fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
> +			    uint32_t offset, void *buffer, size_t *length)
>  {
>  	uint32_t total, remaining = *length;
>  	uint64_t baddr;
>  	uint64_t balign, boff, bsize;
>  	struct fsp_msg *msg;
> -	static struct lock fsp_fetch_lock = LOCK_UNLOCKED;
>  
>  	*length = total = 0;
>  
> @@ -2160,11 +2159,6 @@ int fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
>  	      "(0x%x bytes)\n",
>  	      id, sub_id, buffer, remaining);
>  
> -	/*
> -	 * Use a lock to avoid multiple processors trying to fetch
> -	 * at the same time and colliding on the TCE space
> -	 */
> -	lock(&fsp_fetch_lock);
>  
>  	while(remaining) {
>  		uint32_t chunk, taddr, woffset, wlen;
> @@ -2201,7 +2195,6 @@ int fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
>  
>  		/* XXX Is flash busy (0x3f) a reason for retry ? */
>  		if (rc != 0 && rc != 2) {
> -			unlock(&fsp_fetch_lock);
>  			return -EIO;
>  		}
>  
> @@ -2218,7 +2211,6 @@ int fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
>  		if (wlen < chunk)
>  			break;
>  	}
> -	unlock(&fsp_fetch_lock);
>  
>  	*length = total;
>  
> @@ -2226,6 +2218,37 @@ int fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
>  }
>  
>  /*
> + * Use busy flag to avoid multiple processors trying to fetch
> + * at the same time and colliding on the TCE space
> + */
> +int fsp_fetch_data(uint8_t flags, uint16_t id, uint32_t sub_id,
> +		   uint32_t offset, void *buffer, size_t *length)
> +{
> +	static bool fetch_data_busy = false;
> +	int rc;
> +	static struct lock fsp_fetch_lock = LOCK_UNLOCKED;
> +
> +	for (;;) {
> +		lock(&fsp_fetch_lock);
> +		if (!fetch_data_busy) {
> +			fetch_data_busy = true;
> +			unlock(&fsp_fetch_lock);
> +			break;
> +		}
> +		unlock(&fsp_fetch_lock);
> +		cpu_relax();
> +	}
> +
> +	rc = __fsp_fetch_data(flags, id, sub_id, offset, buffer, length);
> +
> +	lock(&fsp_fetch_lock);
> +	fetch_data_busy = false;
> +	unlock(&fsp_fetch_lock);
> +
> +	return rc;
> +}
> +
> +/*
>   * Asynchronous fsp fetch data call
>   *
>   * Note: