Re: [PATCH] ARM: PL330: Fix driver freeze

[Javi Merino <javi.merino@arm.com>]

On 11/12/11 19:27, Javi Merino wrote:
> Add a req_running field to the pl330_thread to track which request (if
> any) has been submitted to the DMA.  This mechanism replaces the old
> one in which we tried to guess the same by looking at the PC of the
> DMA, which could prevent the driver from sending more requests if it
> didn't guess correctly.
> 
> Signed-off-by: Javi Merino <javi.merino@arm.com>
> Cc: Jassi Brar <jaswinder.singh@linaro.org>
> ---
>  arch/arm/common/pl330.c |  116 ++++++++++++++++++++---------------------------
>  1 files changed, 49 insertions(+), 67 deletions(-)
> 
> diff --git a/arch/arm/common/pl330.c b/arch/arm/common/pl330.c
> index f407a6b..8d8df74 100644
> --- a/arch/arm/common/pl330.c
> +++ b/arch/arm/common/pl330.c
> @@ -221,17 +221,6 @@
>   */
>  #define MCODE_BUFF_PER_REQ	256
>  
> -/*
> - * Mark a _pl330_req as free.
> - * We do it by writing DMAEND as the first instruction
> - * because no valid request is going to have DMAEND as
> - * its first instruction to execute.
> - */
> -#define MARK_FREE(req)	do { \
> -				_emit_END(0, (req)->mc_cpu); \
> -				(req)->mc_len = 0; \
> -			} while (0)
> -
>  /* If the _pl330_req is available to the client */
>  #define IS_FREE(req)	(*((u8 *)((req)->mc_cpu)) == CMD_DMAEND)
>  
> @@ -301,8 +290,10 @@ struct pl330_thread {
>  	struct pl330_dmac *dmac;
>  	/* Only two at a time */
>  	struct _pl330_req req[2];
> -	/* Index of the last submitted request */
> +	/* Index of the last enqueued request */
>  	unsigned lstenq;
> +	/* Index of the last submitted request or -1 if the DMA is stopped */
> +	int req_running;
>  };
>  
>  enum pl330_dmac_state {
> @@ -778,6 +769,22 @@ static inline void _execute_DBGINSN(struct pl330_thread *thrd,
>  	writel(0, regs + DBGCMD);
>  }
>  
> +/*
> + * Mark a _pl330_req as free.
> + * We do it by writing DMAEND as the first instruction
> + * because no valid request is going to have DMAEND as
> + * its first instruction to execute.
> + */
> +static void mark_free(struct pl330_thread *thrd, int idx)
> +{
> +	struct _pl330_req *req = &thrd->req[idx];
> +
> +	_emit_END(0, req->mc_cpu);
> +	req->mc_len = 0;
> +
> +	thrd->req_running = -1;
> +}
> +
>  static inline u32 _state(struct pl330_thread *thrd)
>  {
>  	void __iomem *regs = thrd->dmac->pinfo->base;
> @@ -836,31 +843,6 @@ static inline u32 _state(struct pl330_thread *thrd)
>  	}
>  }
>  
> -/* If the request 'req' of thread 'thrd' is currently active */
> -static inline bool _req_active(struct pl330_thread *thrd,
> -		struct _pl330_req *req)
> -{
> -	void __iomem *regs = thrd->dmac->pinfo->base;
> -	u32 buf = req->mc_bus, pc = readl(regs + CPC(thrd->id));
> -
> -	if (IS_FREE(req))
> -		return false;
> -
> -	return (pc >= buf && pc <= buf + req->mc_len) ? true : false;
> -}
> -
> -/* Returns 0 if the thread is inactive, ID of active req + 1 otherwise */
> -static inline unsigned _thrd_active(struct pl330_thread *thrd)
> -{
> -	if (_req_active(thrd, &thrd->req[0]))
> -		return 1; /* First req active */
> -
> -	if (_req_active(thrd, &thrd->req[1]))
> -		return 2; /* Second req active */
> -
> -	return 0;
> -}
> -
>  static void _stop(struct pl330_thread *thrd)
>  {
>  	void __iomem *regs = thrd->dmac->pinfo->base;
> @@ -892,17 +874,22 @@ static bool _trigger(struct pl330_thread *thrd)
>  	struct _arg_GO go;
>  	unsigned ns;
>  	u8 insn[6] = {0, 0, 0, 0, 0, 0};
> +	int idx;
>  
>  	/* Return if already ACTIVE */
>  	if (_state(thrd) != PL330_STATE_STOPPED)
>  		return true;
>  
> -	if (!IS_FREE(&thrd->req[1 - thrd->lstenq]))
> -		req = &thrd->req[1 - thrd->lstenq];
> -	else if (!IS_FREE(&thrd->req[thrd->lstenq]))
> -		req = &thrd->req[thrd->lstenq];
> -	else
> -		req = NULL;
> +	idx = 1 - thrd->lstenq;
> +	if (!IS_FREE(&thrd->req[idx]))
> +		req = &thrd->req[idx];
> +	else {
> +		idx = thrd->lstenq;
> +		if (!IS_FREE(&thrd->req[idx]))
> +			req = &thrd->req[idx];
> +		else
> +			req = NULL;
> +	}
>  
>  	/* Return if no request */
>  	if (!req || !req->r)
> @@ -933,6 +920,8 @@ static bool _trigger(struct pl330_thread *thrd)
>  	/* Only manager can execute GO */
>  	_execute_DBGINSN(thrd, insn, true);
>  
> +	thrd->req_running = idx;
> +
>  	return true;
>  }
>  
> @@ -1382,8 +1371,8 @@ static void pl330_dotask(unsigned long data)
>  
>  			thrd->req[0].r = NULL;
>  			thrd->req[1].r = NULL;
> -			MARK_FREE(&thrd->req[0]);
> -			MARK_FREE(&thrd->req[1]);
> +			mark_free(thrd, 0);
> +			mark_free(thrd, 1);
>  
>  			/* Clear the reset flag */
>  			pl330->dmac_tbd.reset_chan &= ~(1 << i);
> @@ -1461,14 +1450,12 @@ int pl330_update(const struct pl330_info *pi)
>  
>  			thrd = &pl330->channels[id];
>  
> -			active = _thrd_active(thrd);
> -			if (!active) /* Aborted */
> +			active = thrd->req_running;
> +			if (active == -1) /* Aborted */
>  				continue;
>  
> -			active -= 1;
> -
>  			rqdone = &thrd->req[active];
> -			MARK_FREE(rqdone);
> +			mark_free(thrd, active);
>  
>  			/* Get going again ASAP */
>  			_start(thrd);
> @@ -1509,7 +1496,7 @@ int pl330_chan_ctrl(void *ch_id, enum pl330_chan_op op)
>  	struct pl330_thread *thrd = ch_id;
>  	struct pl330_dmac *pl330;
>  	unsigned long flags;
> -	int ret = 0, active;
> +	int ret = 0, active = thrd->req_running;
>  
>  	if (!thrd || thrd->free || thrd->dmac->state == DYING)
>  		return -EINVAL;
> @@ -1525,28 +1512,24 @@ int pl330_chan_ctrl(void *ch_id, enum pl330_chan_op op)
>  
>  		thrd->req[0].r = NULL;
>  		thrd->req[1].r = NULL;
> -		MARK_FREE(&thrd->req[0]);
> -		MARK_FREE(&thrd->req[1]);
> +		mark_free(thrd, 0);
> +		mark_free(thrd, 1);
>  		break;
>  
>  	case PL330_OP_ABORT:
> -		active = _thrd_active(thrd);
> -
>  		/* Make sure the channel is stopped */
>  		_stop(thrd);
>  
>  		/* ABORT is only for the active req */
> -		if (!active)
> +		if (active == -1)
>  			break;
>  
> -		active--;
> -
>  		thrd->req[active].r = NULL;
> -		MARK_FREE(&thrd->req[active]);
> +		mark_free(thrd, active);
>  
>  		/* Start the next */
>  	case PL330_OP_START:
> -		if (!_thrd_active(thrd) && !_start(thrd))
> +		if ((active == -1) && !_start(thrd))
>  			ret = -EIO;
>  		break;
>  
> @@ -1587,14 +1570,13 @@ int pl330_chan_status(void *ch_id, struct pl330_chanstatus *pstatus)
>  	else
>  		pstatus->faulting = false;
>  
> -	active = _thrd_active(thrd);
> +	active = thrd->req_running;
>  
> -	if (!active) {
> +	if (active == -1) {
>  		/* Indicate that the thread is not running */
>  		pstatus->top_req = NULL;
>  		pstatus->wait_req = NULL;
>  	} else {
> -		active--;
>  		pstatus->top_req = thrd->req[active].r;
>  		pstatus->wait_req = !IS_FREE(&thrd->req[1 - active])
>  					? thrd->req[1 - active].r : NULL;
> @@ -1659,9 +1641,9 @@ void *pl330_request_channel(const struct pl330_info *pi)
>  				thrd->free = false;
>  				thrd->lstenq = 1;
>  				thrd->req[0].r = NULL;
> -				MARK_FREE(&thrd->req[0]);
> +				mark_free(thrd, 0);
>  				thrd->req[1].r = NULL;
> -				MARK_FREE(&thrd->req[1]);
> +				mark_free(thrd, 1);
>  				break;
>  			}
>  		}
> @@ -1767,14 +1749,14 @@ static inline void _reset_thread(struct pl330_thread *thrd)
>  	thrd->req[0].mc_bus = pl330->mcode_bus
>  				+ (thrd->id * pi->mcbufsz);
>  	thrd->req[0].r = NULL;
> -	MARK_FREE(&thrd->req[0]);
> +	mark_free(thrd, 0);
>  
>  	thrd->req[1].mc_cpu = thrd->req[0].mc_cpu
>  				+ pi->mcbufsz / 2;
>  	thrd->req[1].mc_bus = thrd->req[0].mc_bus
>  				+ pi->mcbufsz / 2;
>  	thrd->req[1].r = NULL;
> -	MARK_FREE(&thrd->req[1]);
> +	mark_free(thrd, 1);
>  }
>  
>  static int dmac_alloc_threads(struct pl330_dmac *pl330)

I've done some testing and I haven't been able to break it.  Can
somebody please test this patch with the workload that failed (audio in
exynos I believe)?

Thanks,
Javi