[PATCH 2/2] nvme/quirk: Add a delay before checking for adapter readiness

Tue Apr 12 13:31:10 PDT 2016

Hi Guilherme,

Thanks for the clarification. I’ll followup with the product support team here and attempt to re-create.

Dave

On 4/12/16, 3:12 PM, "Guilherme G. Piccoli" <gpiccoli at linux.vnet.ibm.com> wrote:

>On 04/12/2016 02:58 PM, David Darrington wrote:
>> When you say, “This quirk is necessary because just
>> increasing the timeout is not enough - the driver must wait _before_
>> start reading NVME_REG_CSTS register on this specific adapter.,”
>> This doesn’t make sense to me. I’ve never seen this with the
>> HGST adapters. Have you reported this to HGST as a problem?
>
>Hey David, thanks very much for your comment. We're experiencing this 
>exact scenario, as described in commit message. Whenever the adapter 
>needs to be disabled, if we don't wait before reading the NVME_CSTS_RDY 
>bit, we end up reaching the timeout. The read result from this register 
>become 0xFFFF in sme time, and adapter is not able to finish the reset.
>
>If, on the other hand, we add this small timeout before start reading 
>the NVME_REG_CSTS register, everything works fine. Notice this patch is 
>a quirk, so if you are able to reproduce and have a firmware solution, 
>for example, it'd be better.
>
>Problem was reported to HGST (Murali is our contact) and the product 
>team is unable to find a root cause yet, while testers are hitting the 
>issue.
>
>Thank you,
>
>
>
>Guilherme
>
>
>>
>> On 4/11/16, 3:15 PM, "Linux-nvme on behalf of Guilherme G. Piccoli" <linux-nvme-bounces at lists.infradead.org on behalf of gpiccoli at linux.vnet.ibm.com> wrote:
>>
>>> When disabling the controller, the specification says the register
>>> NVME_REG_CC should be written and then driver needs to wait the
>>> adapter to be ready, which is checked by reading another register
>>> bit (NVME_CSTS_RDY). There's a timeout validation in this checking,
>>> so in case this timeout is reached the driver gives up and removes
>>> the adapter from the system.
>>>
>>> The PCI_DEVICE(0x1c58, 0x0003) (HGST adapter) end up being removed
>>> after a reset because driver keeps verifying the NVME_REG_CSTS until
>>> the timeout is reached. This patch adds a quirk for this adapter, by
>>> introducing a delay before nvme_wait_ready(), so the reset procedure
>>> is able to be completed. This quirk is necessary because just
>>> increasing the timeout is not enough - the driver must wait _before_
>>> start reading NVME_REG_CSTS register on this specific adapter.
>>>
>>> Signed-off-by: Guilherme G. Piccoli <gpiccoli at linux.vnet.ibm.com>
>>> ---
>>> drivers/nvme/host/core.c |  4 ++++
>>> drivers/nvme/host/nvme.h | 13 +++++++++++++
>>> drivers/nvme/host/pci.c  |  2 ++
>>> 3 files changed, 19 insertions(+)
>>>
>>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>>> index 643f457..37817bb 100644
>>> --- a/drivers/nvme/host/core.c
>>> +++ b/drivers/nvme/host/core.c
>>> @@ -824,6 +824,10 @@ int nvme_disable_ctrl(struct nvme_ctrl *ctrl, u64 cap)
>>> 	ret = ctrl->ops->reg_write32(ctrl, NVME_REG_CC, ctrl->ctrl_config);
>>> 	if (ret)
>>> 		return ret;
>>> +
>>> +	if (ctrl->quirks & NVME_QUIRK_DELAY_BEFORE_CHECK_RDY)
>>> +		msleep(NVME_QUIRK_DELAY_AMOUNT_MS);
>>> +
>>> 	return nvme_wait_ready(ctrl, cap, false);
>>> }
>>> EXPORT_SYMBOL_GPL(nvme_disable_ctrl);
>>> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
>>> index f846da4..b8247c4 100644
>>> --- a/drivers/nvme/host/nvme.h
>>> +++ b/drivers/nvme/host/nvme.h
>>> @@ -65,8 +65,21 @@ enum nvme_quirks {
>>> 	 * logical blocks.
>>> 	 */
>>> 	NVME_QUIRK_DISCARD_ZEROES		= (1 << 2),
>>> +
>>> +	/*
>>> +	* The controller needs a delay before starts checking the device
>>> +	* readiness, which is done by reading the NVME_CSTS_RDY bit.
>>> +	*/
>>> +	NVME_QUIRK_DELAY_BEFORE_CHECK_RDY	= (1 << 3),
>>> };
>>>
>>> +/* The below value is the specific amount of delay needed before checking
>>> + * readiness in case of the PCI_DEVICE(0x1c58, 0x0003), which needs the
>>> + * NVME_QUIRK_DELAY_BEFORE_CHECK_RDY quirk enabled. The value was found
>>> + * empirically. The value is in milliseconds.
>>> + */
>>> +#define NVME_QUIRK_DELAY_AMOUNT_MS		2000
>>> +
>>> struct nvme_ctrl {
>>> 	const struct nvme_ctrl_ops *ops;
>>> 	struct request_queue *admin_q;
>>> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
>>> index 220e0b5..a5e3d0e 100644
>>> --- a/drivers/nvme/host/pci.c
>>> +++ b/drivers/nvme/host/pci.c
>>> @@ -2173,6 +2173,8 @@ static const struct pci_device_id nvme_id_table[] = {
>>> 	{ PCI_VDEVICE(INTEL, 0x5845),	/* Qemu emulated controller */
>>> 		.driver_data = NVME_QUIRK_IDENTIFY_CNS, },
>>> 	{ PCI_DEVICE(PCI_VENDOR_ID_APPLE, 0x2001) },
>>> +	{ PCI_DEVICE(0x1c58, 0x0003),	/*HGST adapter */
>>> +		.driver_data = NVME_QUIRK_DELAY_BEFORE_CHECK_RDY, },
>>> 	{ PCI_DEVICE_CLASS(PCI_CLASS_STORAGE_EXPRESS, 0xffffff) },
>>> 	{ 0, }
>>> };
>>> --
>>> 2.1.0
>>>
>>>
>>> _______________________________________________
>>> Linux-nvme mailing list
>>> Linux-nvme at lists.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/linux-nvme
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