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Subject[PATCH] Fix for initialize drives not capable to handle maximum bandwidth
Date
In some cases if sata drive can't work with default controller
bandwidth, driver fails to initialize the device.

libata-core: sata_link_hardreset - if after reset the device is
offline, then driver should try again, with lower SPD.

sata_down_spd_limit - function should handle corner case values,
if device is not initialized yet.

Bugzilla: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1783906

Signed-off-by: Michał Wadowski <wadosm@gmail.com>
---
drivers/ata/libata-core.c | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index adf28788cab5..a37249c4ebeb 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -3061,6 +3061,7 @@ int sata_down_spd_limit(struct ata_link *link, u32 spd_limit)

/* If SCR can be read, use it to determine the current SPD.
* If not, use cached value in link->sata_spd.
+ * Value of link->sata_spd may be 0.
*/
rc = sata_scr_read(link, SCR_STATUS, &sstatus);
if (rc == 0 && ata_sstatus_online(sstatus))
@@ -3072,23 +3073,23 @@ int sata_down_spd_limit(struct ata_link *link, u32 spd_limit)
if (mask <= 1)
return -EINVAL;

+ /* sata_spd_limit may by initially INT_MAX, that is not correct
+ * value to working with. Cut down mask to highest correct value.
+ */
+ mask &= 0x7;
+
/* unconditionally mask off the highest bit */
bit = fls(mask) - 1;
mask &= ~(1 << bit);

/*
- * Mask off all speeds higher than or equal to the current one. At
- * this point, if current SPD is not available and we previously
- * recorded the link speed from SStatus, the driver has already
- * masked off the highest bit so mask should already be 1 or 0.
- * Otherwise, we should not force 1.5Gbps on a link where we have
- * not previously recorded speed from SStatus. Just return in this
- * case.
+ * Mask off all speeds higher than or equal to the current one.
+ * If device is not initialized yet, value of SPD is 0, so
+ * we should ignore this. If spd is 1, then we can't speed down
+ * any more.
*/
if (spd > 1)
mask &= (1 << (spd - 1)) - 1;
- else
- return -EINVAL;

/* were we already at the bottom? */
if (!mask)
@@ -4116,7 +4117,10 @@ int sata_link_hardreset(struct ata_link *link, const unsigned long *timing,
goto out;
/* if link is offline nothing more to do */
if (ata_phys_link_offline(link))
+ {
+ rc = -EPIPE;
goto out;
+ }

/* Link is online. From this point, -ENODEV too is an error. */
if (online)
--
2.7.4
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