Date:	Thu, 16 Oct 2008 07:42:39 +0200
From:	Borislav Petkov <petkovbb@...glemail.com>
To:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
Cc:	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ide-cd: remove obsolete seek optimization

On Wed, Oct 15, 2008 at 09:47:47PM +0200, Bartlomiej Zolnierkiewicz wrote:
> It doesn't make much sense nowadays and is problematic on some drives.

This is a big chunk, after all. We should do more hammering on it though, just
to be sure.

> Cc: Borislav Petkov <petkovbb@...glemail.com>
> Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
> ---
> against pata tree
> 
>  drivers/ide/ide-cd.c |   89 +++------------------------------------------------
>  drivers/ide/ide-cd.h |    2 -
>  include/linux/ide.h  |    4 --
>  3 files changed, 6 insertions(+), 89 deletions(-)
> 
> Index: b/drivers/ide/ide-cd.c
> ===================================================================
> --- a/drivers/ide/ide-cd.c
> +++ b/drivers/ide/ide-cd.c
> @@ -774,52 +774,6 @@ static ide_startstop_t cdrom_start_rw_co
>  	return cdrom_transfer_packet_command(drive, rq, cdrom_newpc_intr);
>  }
>  
> -#define IDECD_SEEK_THRESHOLD	(1000)			/* 1000 blocks */
> -#define IDECD_SEEK_TIMER	(5 * WAIT_MIN_SLEEP)	/* 100 ms */
> -#define IDECD_SEEK_TIMEOUT	(2 * WAIT_CMD)		/* 20 sec */
> -
> -static ide_startstop_t cdrom_seek_intr(ide_drive_t *drive)
> -{
> -	struct cdrom_info *info = drive->driver_data;
> -	int stat;
> -	static int retry = 10;
> -
> -	ide_debug_log(IDE_DBG_FUNC, "Call %s\n", __func__);
> -
> -	if (cdrom_decode_status(drive, 0, &stat))
> -		return ide_stopped;
> -
> -	drive->atapi_flags |= IDE_AFLAG_SEEKING;
> -
> -	if (retry && time_after(jiffies, info->start_seek + IDECD_SEEK_TIMER)) {
> -		if (--retry == 0)
> -			drive->dev_flags &= ~IDE_DFLAG_DSC_OVERLAP;
> -	}
> -	return ide_stopped;
> -}
> -
> -static void ide_cd_prepare_seek_request(ide_drive_t *drive, struct request *rq)
> -{
> -	sector_t frame = rq->sector;
> -
> -	ide_debug_log(IDE_DBG_FUNC, "Call %s\n", __func__);
> -
> -	sector_div(frame, queue_hardsect_size(drive->queue) >> SECTOR_BITS);
> -
> -	memset(rq->cmd, 0, BLK_MAX_CDB);
> -	rq->cmd[0] = GPCMD_SEEK;
> -	put_unaligned(cpu_to_be32(frame), (unsigned int *) &rq->cmd[2]);
> -
> -	rq->timeout = ATAPI_WAIT_PC;
> -}
> -
> -static ide_startstop_t cdrom_start_seek_continuation(ide_drive_t *drive)
> -{
> -	struct request *rq = drive->hwif->hwgroup->rq;
> -
> -	return cdrom_transfer_packet_command(drive, rq, &cdrom_seek_intr);
> -}
> -
>  /*
>   * Fix up a possibly partially-processed request so that we can start it over
>   * entirely, or even put it back on the request queue.
> @@ -1259,7 +1213,6 @@ static void cdrom_do_block_pc(ide_drive_
>  static ide_startstop_t ide_cd_do_request(ide_drive_t *drive, struct request *rq,
>  					sector_t block)
>  {
> -	struct cdrom_info *info = drive->driver_data;
>  	ide_handler_t *fn;
>  	int xferlen;
>  
> @@ -1269,44 +1222,14 @@ static ide_startstop_t ide_cd_do_request
>  		      (unsigned long long)block);
>  
>  	if (blk_fs_request(rq)) {
> -		if (drive->atapi_flags & IDE_AFLAG_SEEKING) {
> -			ide_hwif_t *hwif = drive->hwif;
> -			unsigned long elapsed = jiffies - info->start_seek;
> -			int stat = hwif->tp_ops->read_status(hwif);
> -
> -			if ((stat & ATA_DSC) != ATA_DSC) {
> -				if (elapsed < IDECD_SEEK_TIMEOUT) {
> -					ide_stall_queue(drive,
> -							IDECD_SEEK_TIMER);
> -					return ide_stopped;
> -				}
> -				printk(KERN_ERR PFX "%s: DSC timeout\n",
> -						drive->name);
> -			}
> -			drive->atapi_flags &= ~IDE_AFLAG_SEEKING;
> -		}
> -		if (rq_data_dir(rq) == READ &&
> -		    IDE_LARGE_SEEK(info->last_block, block,
> -			    IDECD_SEEK_THRESHOLD) &&
> -		    (drive->dev_flags & IDE_DFLAG_DSC_OVERLAP)) {
> -			xferlen = 0;
> -			fn = cdrom_start_seek_continuation;
> -
> -			drive->dma = 0;
> -			info->start_seek = jiffies;
> -
> -			ide_cd_prepare_seek_request(drive, rq);
> -		} else {
> -			xferlen = 32768;
> -			fn = cdrom_start_rw_cont;
> +		xferlen = 32768;
> +		fn = cdrom_start_rw_cont;
>  
> -			if (cdrom_start_rw(drive, rq) == ide_stopped)
> -				return ide_stopped;
> +		if (cdrom_start_rw(drive, rq) == ide_stopped)
> +			return ide_stopped;
>  
> -			if (ide_cd_prepare_rw_request(drive, rq) == ide_stopped)
> -				return ide_stopped;
> -		}
> -		info->last_block = block;
> +		if (ide_cd_prepare_rw_request(drive, rq) == ide_stopped)
> +			return ide_stopped;
>  	} else if (blk_sense_request(rq) || blk_pc_request(rq) ||
>  		   rq->cmd_type == REQ_TYPE_ATA_PC) {
>  		xferlen = rq->data_len;
> Index: b/drivers/ide/ide-cd.h
> ===================================================================
> --- a/drivers/ide/ide-cd.h
> +++ b/drivers/ide/ide-cd.h
> @@ -88,8 +88,6 @@ struct cdrom_info {
>  	struct request_sense sense_data;
>  
>  	struct request request_sense_request;
> -	unsigned long last_block;
> -	unsigned long start_seek;
>  
>  	u8 max_speed;		/* Max speed of the drive. */
>  	u8 current_speed;	/* Current speed of the drive. */
> Index: b/include/linux/ide.h
> ===================================================================
> --- a/include/linux/ide.h
> +++ b/include/linux/ide.h
> @@ -122,8 +122,6 @@ struct ide_io_ports {
>  #define MAX_DRIVES	2	/* per interface; 2 assumed by lots of code */
>  #define SECTOR_SIZE	512
>  
> -#define IDE_LARGE_SEEK(b1,b2,t)	(((b1) > (b2) + (t)) || ((b2) > (b1) + (t)))
> -
>  /*
>   * Timeouts for various operations:
>   */
> @@ -496,8 +494,6 @@ enum {
>  	 * when more than one interrupt is needed.
>  	 */
>  	IDE_AFLAG_LIMIT_NFRAMES		= (1 << 7),
> -	/* Seeking in progress. */
> -	IDE_AFLAG_SEEKING		= (1 << 8),
>  	/* Saved TOC information is current. */
>  	IDE_AFLAG_TOC_VALID		= (1 << 9),
>  	/* We think that the drive door is locked. */

maybe:					= (1 << 8),


-- 
Regards/Gruss,
    Boris.
--
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