libata: support the ata host which implements a queue depth less than 32
The sata on fsl mpc8315e is broken after the commit8a4aeec8d2
("libata/ahci: accommodate tag ordered controllers"). The reason is that the ata controller on this SoC only implement a queue depth of 16. When issuing the commands in tag order, all the commands in tag 16 ~ 31 are mapped to tag 0 unconditionally and then causes the sata malfunction. It makes no senses to use a 32 queue in software while the hardware has less queue depth. So consider the queue depth implemented by the hardware when requesting a command tag. Fixes:8a4aeec8d2
("libata/ahci: accommodate tag ordered controllers") Cc: stable@vger.kernel.org Signed-off-by: Kevin Hao <haokexin@gmail.com> Acked-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Tejun Heo <tj@kernel.org>
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@ -4787,6 +4787,10 @@ void swap_buf_le16(u16 *buf, unsigned int buf_words)
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* ata_qc_new - Request an available ATA command, for queueing
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* @ap: target port
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*
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* Some ATA host controllers may implement a queue depth which is less
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* than ATA_MAX_QUEUE. So we shouldn't allocate a tag which is beyond
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* the hardware limitation.
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*
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* LOCKING:
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* None.
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*/
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@ -4794,14 +4798,16 @@ void swap_buf_le16(u16 *buf, unsigned int buf_words)
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static struct ata_queued_cmd *ata_qc_new(struct ata_port *ap)
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{
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struct ata_queued_cmd *qc = NULL;
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unsigned int i, tag;
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unsigned int i, tag, max_queue;
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max_queue = ap->scsi_host->can_queue;
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/* no command while frozen */
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if (unlikely(ap->pflags & ATA_PFLAG_FROZEN))
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return NULL;
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for (i = 0; i < ATA_MAX_QUEUE; i++) {
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tag = (i + ap->last_tag + 1) % ATA_MAX_QUEUE;
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for (i = 0, tag = ap->last_tag + 1; i < max_queue; i++, tag++) {
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tag = tag < max_queue ? tag : 0;
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/* the last tag is reserved for internal command. */
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if (tag == ATA_TAG_INTERNAL)
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@ -6169,6 +6175,16 @@ int ata_host_register(struct ata_host *host, struct scsi_host_template *sht)
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{
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int i, rc;
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/*
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* The max queue supported by hardware must not be greater than
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* ATA_MAX_QUEUE.
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*/
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if (sht->can_queue > ATA_MAX_QUEUE) {
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dev_err(host->dev, "BUG: the hardware max queue is too large\n");
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WARN_ON(1);
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return -EINVAL;
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}
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/* host must have been started */
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if (!(host->flags & ATA_HOST_STARTED)) {
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dev_err(host->dev, "BUG: trying to register unstarted host\n");
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