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nvme: set controller enable bit in a separate write

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The NVM Express Base Specification 2.0 specifies in the description
of the CC – Controller Configuration register:
"Host software shall set the Arbitration Mechanism Selected (CC.AMS),
the Memory Page Size (CC.MPS), and the I/O Command Set Selected (CC.CSS)
to valid values prior to enabling the controller by setting CC.EN to ‘1’.

While we haven't seen any controller misbehaving while setting all bits
in a single write, let's do it in the order that it is written in the
spec, as there could potentially be controllers that are implemented to
rely on the configuration bits being set before enabling the controller.

Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Niklas Cassel 2022-05-26 15:57:21 +02:00 committed by Christoph Hellwig
parent 70ce345534
commit aa41d2fe60
1 changed files with 9 additions and 1 deletions
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10
drivers/nvme/host/core.c
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@ -2227,8 +2227,16 @@ int nvme_enable_ctrl(struct nvme_ctrl *ctrl)
ctrl->ctrl_config |= (NVME_CTRL_PAGE_SHIFT - 12) << NVME_CC_MPS_SHIFT;
ctrl->ctrl_config |= NVME_CC_AMS_RR | NVME_CC_SHN_NONE;
ctrl->ctrl_config |= NVME_CC_IOSQES | NVME_CC_IOCQES;
ctrl->ctrl_config |= NVME_CC_ENABLE;
ret = ctrl->ops->reg_write32(ctrl, NVME_REG_CC, ctrl->ctrl_config);
if (ret)
return ret;
/* Flush write to device (required if transport is PCI) */
ret = ctrl->ops->reg_read32(ctrl, NVME_REG_CC, &ctrl->ctrl_config);
if (ret)
return ret;
ctrl->ctrl_config |= NVME_CC_ENABLE;
ret = ctrl->ops->reg_write32(ctrl, NVME_REG_CC, ctrl->ctrl_config);
if (ret)
return ret;