[SCSI] sd: pause in sd_spinup_disk for slow USB devices

This patch adds a delay tailored for USB flash devices that are slow to
initialize their firmware.  The symptom is a repeated Unit Attention with
ASC=0x28 (Not Ready to Ready transition).  The patch will wait for up to 5
seconds for such devices to become ready.  Normal devices won't send the
repeated Unit Attention sense key and hence won't trigger the patch.

This fixes a problem with James Roberts-Thomson's USB device, and I've
seen several reports of other devices exhibiting the same symptoms --
presumably they will be helped as well.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

1 files changed, 19 insertions, 5 deletions

diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
index 0410e1bf109a..41ba0809f791 100644
--- a/drivers/scsi/sd.c
+++ b/drivers/scsi/sd.c
@@ -984,7 +984,7 @@ static void
 sd_spinup_disk(struct scsi_disk *sdkp, char *diskname,
                struct scsi_request *SRpnt, unsigned char *buffer) {
         unsigned char cmd[10];
-        unsigned long spintime_value = 0;
+        unsigned long spintime_expire = 0;
         int retries, spintime;
         unsigned int the_result;
         struct scsi_sense_hdr sshdr;
@@ -1071,12 +1071,27 @@ sd_spinup_disk(struct scsi_disk *sdkp, char *diskname,
                                 scsi_wait_req(SRpnt, (void *)cmd, 
                                               (void *) buffer, 0/*512*/, 
                                               SD_TIMEOUT, SD_MAX_RETRIES);
-                                spintime_value = jiffies;
+                                spintime_expire = jiffies + 100 * HZ;
+                                spintime = 1;
                         }
-                        spintime = 1;
                         /* Wait 1 second for next try */
                         msleep(1000);
                         printk(".");
+
+                /*
+                 * Wait for USB flash devices with slow firmware.
+                 * Yes, this sense key/ASC combination shouldn't
+                 * occur here.  It's characteristic of these devices.
+                 */
+                } else if (sense_valid &&
+                                sshdr.sense_key == UNIT_ATTENTION &&
+                                sshdr.asc == 0x28) {
+                        if (!spintime) {
+                                spintime_expire = jiffies + 5 * HZ;
+                                spintime = 1;
+                        }
+                        /* Wait 1 second for next try */
+                        msleep(1000);
                 } else {
                         /* we don't understand the sense code, so it's
                          * probably pointless to loop */
@@ -1088,8 +1103,7 @@ sd_spinup_disk(struct scsi_disk *sdkp, char *diskname,
                         break;
                 }
                                 
-        } while (spintime &&
-                 time_after(spintime_value + 100 * HZ, jiffies));
+        } while (spintime && time_before_eq(jiffies, spintime_expire));
 
         if (spintime) {
                 if (scsi_status_is_good(the_result))