[2.4 PATCH:] Lengthen SCSI timeouts to deal with broken hardware

linas_at_austin.ibm.com
Date: 09/30/03

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    Date:	Tue, 30 Sep 2003 12:09:44 -0500
To: linux-kernel@vger.kernel.org

    [PATCH: 2.4] Lengthen SCSI timeouts to deal with broken hardware

    Hi,

    The following patch lengthens some scsi timeouts to deal with some
    misbehaving hardware. The device in question is an Achip ARC765-based
    ide-to-scsi converter that is used to attach IDE DVD-ROMS to scsi
    chains. This device can take a very long time (10-15 seconds) to
    get back to a normal state after a bus reset, causing the scsi layer
    to timeout on commands issued after the reset.

    We measured these timeouts using a SCSI bus analyzer. Our guess is
    that the slow IDE-CDROM behind this device is helping make the response
    times exceptionally large.

    The patch below is minimalistic, and not at all fancy. Its also marked
    as a __powerpc64__ patch, because this device commonly ships with ppc64
    machines. Precisely speaking, though, this is not an architecture
    specific problem, anyone with this Achip/Acard will see the (hardware)
    bug. I suspect this is a rare, obscure device on non-ppc64 machines.
    I've made the patch a __powerpc64__ patch so as to limit impact and
    complaints and reasons for rejecting this patch.

    --linas

    --- drivers/scsi/scsi_obsolete.c.orig 2003-09-29 17:47:26.000000000 -0500
    +++ drivers/scsi/scsi_obsolete.c 2003-09-29 17:51:40.000000000 -0500
    @@ -118,10 +118,19 @@ static void scsi_dump_status(void);
     #define ABORT_TIMEOUT SCSI_TIMEOUT
     #define RESET_TIMEOUT SCSI_TIMEOUT
     #else
    +#if defined(__powerpc64__)
    +/* Some Achip ARC765-based DVD-ROM's can take 15 seconds or more to reset.
    + * All commands (sense, abort) will not get a response until the reset
    + * completes. Lengthen timeouts to make up for this. */
    +#define SENSE_TIMEOUT (20*HZ)
    +#define RESET_TIMEOUT (2*HZ)
    +#define ABORT_TIMEOUT (25*HZ)
    +#else
     #define SENSE_TIMEOUT (5*HZ/10)
     #define RESET_TIMEOUT (5*HZ/10)
     #define ABORT_TIMEOUT (5*HZ/10)
     #endif
    +#endif
     
     
     /* Do not call reset on error if we just did a reset within 15 sec. */
    --- drivers/scsi/scsi_scan.c.orig 2003-09-29 17:52:11.000000000 -0500
    +++ drivers/scsi/scsi_scan.c 2003-09-29 17:56:58.000000000 -0500
    @@ -23,6 +23,15 @@
     #include <linux/kmod.h>
     #endif
     
    +#if defined(__powerpc64__)
    +/* Some Achip ARC765-based DVD-ROM's can take 15 seconds or more to reset.
    + * All commands (sense, abort) will not get a response until the reset
    + * completes. Lengthen timeouts to make up for this. */
    +#define SCSI_INQ_TIMEOUT (SCSI_TIMEOUT+25*HZ)
    +#else
    +#define SCSI_INQ_TIMEOUT (SCSI_TIMEOUT+4*HZ)
    +#endif
    +
     /*
      * Flags for irregular SCSI devices that need special treatment
      */
    @@ -602,7 +611,7 @@ static int scan_scsis_single(unsigned in
     
             scsi_wait_req (SRpnt, (void *) scsi_cmd,
                       (void *) scsi_result,
    - 256, SCSI_TIMEOUT+4*HZ, 3);
    + 256, SCSI_INQ_TIMEOUT, 3);
     
             SCSI_LOG_SCAN_BUS(3, printk("scsi: INQUIRY %s with code 0x%x\n",
                     SRpnt->sr_result ? "failed" : "successful", SRpnt->sr_result));
    -
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