libata: Allow NCQ TRIM to be enabled or disabled with a module parameter

We have started seeing SSD firmware updates introduce support for queued
TRIM. Sadly, in most cases this support is completely untested and can
lead to either errors or data corruption.

Add two libata force flags that can be used to either enable or disable
queued TRIM support.
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Tejun Heo <tj@kernel.org>

Documentation/kernel-parameters.txt

@@ -1755,6 +1755,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 			* [no]ncq: Turn on or off NCQ.
 
+			* [no]ncqtrim: Turn off queued DSM TRIM.
+
 			* nohrst, nosrst, norst: suppress hard, soft
                           and both resets.
 

drivers/ata/libata-core.c

@@ -6472,6 +6472,8 @@ static int __init ata_parse_force_one(char **cur,
 		{ "3.0Gbps",	.spd_limit	= 2 },
 		{ "noncq",	.horkage_on	= ATA_HORKAGE_NONCQ },
 		{ "ncq",	.horkage_off	= ATA_HORKAGE_NONCQ },
+		{ "noncqtrim",	.horkage_on	= ATA_HORKAGE_NO_NCQ_TRIM },
+		{ "ncqtrim",	.horkage_off	= ATA_HORKAGE_NO_NCQ_TRIM },
 		{ "dump_id",	.horkage_on	= ATA_HORKAGE_DUMP_ID },
 		{ "pio0",	.xfer_mask	= 1 << (ATA_SHIFT_PIO + 0) },
 		{ "pio1",	.xfer_mask	= 1 << (ATA_SHIFT_PIO + 1) },