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SubjectRe: [PATCH 2/3] nvme: Retrieve the required IO queue entry size from the controller
> +	/* Use default IOSQES. We'll update it later if needed */
> ctrl->ctrl_config |= NVME_CC_IOSQES | NVME_CC_IOCQES;
> ctrl->ctrl_config |= NVME_CC_ENABLE;
>
> @@ -2698,6 +2699,30 @@ int nvme_init_identify(struct nvme_ctrl *ctrl)
> ctrl->hmmin = le32_to_cpu(id->hmmin);
> ctrl->hmminds = le32_to_cpu(id->hmminds);
> ctrl->hmmaxd = le16_to_cpu(id->hmmaxd);
> +
> + /* Grab required IO queue size */
> + ctrl->iosqes = id->sqes & 0xf;
> + if (ctrl->iosqes < NVME_NVM_IOSQES) {
> + dev_err(ctrl->device,
> + "unsupported required IO queue size %d\n", ctrl->iosqes);
> + ret = -EINVAL;
> + goto out_free;
> + }
> + /*
> + * If our IO queue size isn't the default, update the setting
> + * in CC:IOSQES.
> + */
> + if (ctrl->iosqes != NVME_NVM_IOSQES) {
> + ctrl->ctrl_config &= ~(0xfu << NVME_CC_IOSQES_SHIFT);
> + ctrl->ctrl_config |= ctrl->iosqes << NVME_CC_IOSQES_SHIFT;
> + ret = ctrl->ops->reg_write32(ctrl, NVME_REG_CC,
> + ctrl->ctrl_config);
> + if (ret) {
> + dev_err(ctrl->device,
> + "error updating CC register\n");
> + goto out_free;
> + }
> + }

Actually, this doesn't work on a "real" nvme controller, to change CC
values the controller needs to be disabled. So back to the version
you circulated to me in private mail that just sets q->sqes and has a
comment that this is magic for The Apple controller. If/when we get
standardized large SQE support we'll need to discover that earlier or
do a disable/enable dance. Sorry for misleading you down this road and
creating the extra work.

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