dmaengine: pl330: fix double lock

The static bug finder EBA (http://www.iagoabal.eu/eba/) reported the
following double-lock bug:

    Double lock:
    1. spin_lock_irqsave(pch->lock, flags) at pl330_free_chan_resources:2236;
    2. call to function `pl330_release_channel' immediately after;
    3. call to function `dma_pl330_rqcb' in line 1753;
    4. spin_lock_irqsave(pch->lock, flags) at dma_pl330_rqcb:1505.

I have fixed it as suggested by Marek Szyprowski.

First, I have replaced `pch->lock' with `pl330->lock' in functions
`pl330_alloc_chan_resources' and `pl330_free_chan_resources'. This avoids
the double-lock by acquiring a different lock than `dma_pl330_rqcb'.

NOTE that, as a result, `pl330_free_chan_resources' executes
`list_splice_tail_init' on `pch->work_list' under lock `pl330->lock',
whereas in the rest of the code `pch->work_list' is protected by
`pch->lock'. I don't know if this may cause race conditions. Similarly
`pch->cyclic' is written by `pl330_alloc_chan_resources' under
`pl330->lock' but read by `pl330_tx_submit' under `pch->lock'.

Second, I have removed locking from `pl330_request_channel' and
`pl330_release_channel' functions. Function `pl330_request_channel' is
only called from `pl330_alloc_chan_resources', so the lock is already
held. Function `pl330_release_channel' is called from
`pl330_free_chan_resources', which already holds the lock, and from
`pl330_del'. Function `pl330_del' is called in an error path of
`pl330_probe' and at the end of `pl330_remove', but I assume that there
cannot be concurrent accesses to the protected data at those points.

Signed-off-by: Iago Abal <mail@iagoabal.eu>
Reviewed-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

path: root/include/net/ax88796.h

/* include/net/ax88796.h
 *
 * Copyright 2005 Simtec Electronics
 *	Ben Dooks <ben@simtec.co.uk>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
*/

#ifndef __NET_AX88796_PLAT_H
#define __NET_AX88796_PLAT_H

#define AXFLG_HAS_EEPROM		(1<<0)
#define AXFLG_MAC_FROMDEV		(1<<1)	/* device already has MAC */
#define AXFLG_HAS_93CX6			(1<<2)	/* use eeprom_93cx6 driver */
#define AXFLG_MAC_FROMPLATFORM		(1<<3)	/* MAC given by platform data */

struct ax_plat_data {
	unsigned int	 flags;
	unsigned char	 wordlength;	/* 1 or 2 */
	unsigned char	 dcr_val;	/* default value for DCR */
	unsigned char	 rcr_val;	/* default value for RCR */
	unsigned char	 gpoc_val;	/* default value for GPOC */
	u32		*reg_offsets;	/* register offsets */
	u8		*mac_addr;	/* MAC addr (only used when
					   AXFLG_MAC_FROMPLATFORM is used */
};

#endif /* __NET_AX88796_PLAT_H */