[PATCH] ide-scsi driver starts DMA too soon

Khalid Aziz (khalid@fc.hp.com)
Fri, 1 Nov 2002 16:39:52 -0700 (MST)


ide-scsi driver starts DMA as soon as it writes the ATAPI PACKET command
in command register and before sending the ATAPI command. This will
cause problems on many drives. Right way to do it is to start DMA after
sending the ATAPI command. I am attaching a patch that fixes this. This
patch will allow many more CD-RW drives to work reliably in DMA mode
than do today.

Marcelo, please apply.

--
Khalid

==================================================================== Khalid Aziz Linux and Open Source Lab (970)898-9214 Hewlett-Packard khalid@hp.com Fort Collins, CO

-----------CUT HERE-------------CUT HERE-------------CUT HERE----------- --- linux-2.4.19/drivers/scsi/ide-scsi.c Fri Aug 2 18:39:44 2002 +++ linux-2.4.19.cd_dma/drivers/scsi/ide-scsi.c Fri Nov 1 16:31:30 2002 @@ -397,6 +397,8 @@ idescsi_pc_t *pc = scsi->pc; byte ireason; ide_startstop_t startstop; + struct request *rq = pc->rq; + int dma_ok = 0; if (ide_wait_stat (&startstop,drive,DRQ_STAT,BUSY_STAT,WAIT_READY)) { printk (KERN_ERR "ide-scsi: Strange, packet command initiated yet DRQ isn't asserted\n"); @@ -407,8 +409,14 @@ printk (KERN_ERR "ide-scsi: (IO,CoD) != (0,1) while issuing a packet command\n"); return ide_do_reset (drive); } + if (drive->using_dma && rq->bh) + dma_ok=!HWIF(drive)->dmaproc(test_bit (PC_WRITING, &pc->flags) ? ide_dma_write : ide_dma_read, drive); ide_set_handler(drive, &idescsi_pc_intr, get_timeout(pc), NULL); /* Set the interrupt routine */ atapi_output_bytes (drive, scsi->pc->c, 12); /* Send the actual packet */ + if (dma_ok) { + set_bit (PC_DMA_IN_PROGRESS, &pc->flags); + (void) (HWIF(drive)->dmaproc(ide_dma_begin, drive)); + } return ide_started; } @@ -437,10 +445,6 @@ OUT_BYTE (bcount >> 8,IDE_BCOUNTH_REG); OUT_BYTE (bcount & 0xff,IDE_BCOUNTL_REG); - if (dma_ok) { - set_bit (PC_DMA_IN_PROGRESS, &pc->flags); - (void) (HWIF(drive)->dmaproc(ide_dma_begin, drive)); - } if (test_bit (IDESCSI_DRQ_INTERRUPT, &scsi->flags)) { ide_set_handler (drive, &idescsi_transfer_pc, get_timeout(pc), NULL); OUT_BYTE (WIN_PACKETCMD, IDE_COMMAND_REG); /* Issue the packet command */ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/