[PATCH v1 0/1] ufs: core: Add host quirk QUIRK_MCQ_EXPAND_QUEUE_SLOT

[PATCH v1 0/1] ufs: core: Add host quirk QUIRK_MCQ_EXPAND_QUEUE_SLOT

[Chun-Hung Wu]

Support quirk for host controller not able to distinguish
queue full or empty.

Alice Chao (1):
  ufs: core: Add host quirk QUIRK_MCQ_EXPAND_QUEUE_SLOT

 drivers/ufs/core/ufs-mcq.c |  5 ++++-
 include/ufs/ufshcd.h       | 11 +++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

-- 
2.18.0

[PATCH v1 1/1] ufs: core: Add host quirk QUIRK_MCQ_EXPAND_QUEUE_SLOT

[Chun-Hung Wu]

From: Alice Chao <alice.chao@mediatek.com>

This quirk needs to be enabled if the host controller cannot
distinguish queue full or empty.

Signed-off-by: Alice Chao <alice.chao@mediatek.com>
---
 drivers/ufs/core/ufs-mcq.c |  5 ++++-
 include/ufs/ufshcd.h       | 11 +++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/ufs/core/ufs-mcq.c b/drivers/ufs/core/ufs-mcq.c
index 2ba8ec254dce..9b8ed3f9a349 100644
--- a/drivers/ufs/core/ufs-mcq.c
+++ b/drivers/ufs/core/ufs-mcq.c
@@ -436,7 +436,10 @@ int ufshcd_mcq_init(struct ufs_hba *hba)
 
 	for (i = 0; i < hba->nr_hw_queues; i++) {
 		hwq = &hba->uhq[i];
-		hwq->max_entries = hba->nutrs;
+		if (ufshcd_is_mcq_expand_queue_slot(hba))
+			hwq->max_entries = hba->nutrs + 1;
+		else
+			hwq->max_entries = hba->nutrs;
 		spin_lock_init(&hwq->sq_lock);
 		spin_lock_init(&hwq->cq_lock);
 		mutex_init(&hwq->sq_mutex);
diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
index 7d07b256e906..44de185501b5 100644
--- a/include/ufs/ufshcd.h
+++ b/include/ufs/ufshcd.h
@@ -643,6 +643,12 @@ enum ufshcd_quirks {
 	 * thus need this quirk to skip related flow.
 	 */
 	UFSHCD_QUIRK_MCQ_BROKEN_RTC			= 1 << 21,
+
+	/*
+	 * This quirk needs to be enabled if the host controller cannot
+	 * distinguish queue full or empty.
+	 */
+	UFSHCD_QUIRK_MCQ_EXPAND_QUEUE_SLOT              = 1 << 22,
 };
 
 enum ufshcd_caps {
@@ -1198,6 +1204,11 @@ static inline bool ufshcd_enable_wb_if_scaling_up(struct ufs_hba *hba)
 	return hba->caps & UFSHCD_CAP_WB_WITH_CLK_SCALING;
 }
 
+static inline bool ufshcd_is_mcq_expand_queue_slot(struct ufs_hba *hba)
+{
+	return hba->quirks & UFSHCD_QUIRK_MCQ_EXPAND_QUEUE_SLOT;
+}
+
 #define ufsmcq_writel(hba, val, reg)	\
 	writel((val), (hba)->mcq_base + (reg))
 #define ufsmcq_readl(hba, reg)	\
-- 
2.18.0

Re: [PATCH v1 1/1] ufs: core: Add host quirk QUIRK_MCQ_EXPAND_QUEUE_SLOT

[Bart Van Assche]

On 10/25/23 01:56, Chun-Hung Wu wrote:
> This quirk needs to be enabled if the host controller cannot 
> distinguish queue full or empty.

 From the UFSHCI 4.0 specification: "When the head and tail doorbells are
equal, the queue is empty. [ ... ] When the head and tail doorbells are
not equal, the queue contains queue entries."

How is it possible that a host controller cannot distinguish queue full
or queue empty? Which (head - tail) values cause trouble? More
information is needed.

Thanks,

Bart.

Re: [PATCH v1 1/1] ufs: core: Add host quirk QUIRK_MCQ_EXPAND_QUEUE_SLOT

[Chun-Hung Wu (巫駿宏)]

On Wed, 2023-10-25 at 11:10 -0700, Bart Van Assche wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  On 10/25/23 01:56, Chun-Hung Wu wrote:
> > This quirk needs to be enabled if the host controller cannot 
> > distinguish queue full or empty.
> 
>  From the UFSHCI 4.0 specification: "When the head and tail doorbells
> are
> equal, the queue is empty. [ ... ] When the head and tail doorbells
> are
> not equal, the queue contains queue entries."
> 
> How is it possible that a host controller cannot distinguish queue
> full
> or queue empty? Which (head - tail) values cause trouble? More
> information is needed.
> 
> Thanks,
> 
> Bart.
> 
From UFSHCI 4.0 spec "When the head and tail doorbells are equal, the
queue is empty. *Nothe that this definition means there will always be
one empty queue entry"
One of our platform does not keep one empty queue
entry for CQ full
case, that's  why we need this patch to fix this corner case.

Thanks,
Chun-Hung

Re: [PATCH v1 1/1] ufs: core: Add host quirk QUIRK_MCQ_EXPAND_QUEUE_SLOT

[Bart Van Assche]

On 10/26/23 20:27, Chun-Hung Wu (巫駿宏) wrote:
> From UFSHCI 4.0 spec "When the head and tail doorbells are equal, the
> queue is empty. *Nothe that this definition means there will always be
> one empty queue entry"
> One of our platform does not keep one empty queue
> entry for CQ full
> case, that's  why we need this patch to fix this corner case.

The UFSHCI driver should make sure that there is always one empty queue
entry. Does "platform" in the above text refer to the SoC that includes
the UFSHCI controller?

What is totally unclear to me is why the following code depends on the
UFSHCI controller type:

+		if (ufshcd_is_mcq_expand_queue_slot(hba))
+			hwq->max_entries = hba->nutrs + 1;
+		else
+			hwq->max_entries = hba->nutrs;

Shouldn't hwq->max_entries = hba->nutrs + 1 be used for all UFSHCI 4.0
controllers?

Thanks,

Bart.

Re: [PATCH v1 1/1] ufs: core: Add host quirk QUIRK_MCQ_EXPAND_QUEUE_SLOT

[Chun-Hung Wu (巫駿宏)]

On Fri, 2023-10-27 at 13:55 -0700, Bart Van Assche wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  On 10/26/23 20:27, Chun-Hung Wu (巫駿宏) wrote:
> > From UFSHCI 4.0 spec "When the head and tail doorbells are equal,
> the
> > queue is empty. *Nothe that this definition means there will always
> be
> > one empty queue entry"
> > One of our platform does not keep one empty queue
> > entry for CQ full
> > case, that's  why we need this patch to fix this corner case.
> 
> The UFSHCI driver should make sure that there is always one empty
> queue
> entry. Does "platform" in the above text refer to the SoC that
> includes
> the UFSHCI controller?
Yes here "platform" indicates SoC that includes the UFSHCI controller.
> 
> What is totally unclear to me is why the following code depends on
> the
> UFSHCI controller type:
> 
> +if (ufshcd_is_mcq_expand_queue_slot(hba))
> +hwq->max_entries = hba->nutrs + 1;
> +else
> +hwq->max_entries = hba->nutrs;
> 
> Shouldn't hwq->max_entries = hba->nutrs + 1 be used for all UFSHCI
> 4.0
> controllers?
> 
> Thanks,
> 
> Bart.
> 
I think UFSHCI 4.0 spec "When the head and tail doorbells are equal,the
queue is empty. *Nothe that this definition means there will alwaysbe
one empty queue entry" means that "UFSHCI controller" should always
keep one empty queue entry.
One of our host does not follow the spec, therefore, this host will
treat CQ full(head = tail) as CQ empty (head = tail). That's why we
propose this quirk to expand one queue slot for hosts have such issue.
It will make CQ full(head != tail)[keep one empty queue entry] not
equal to CQ empty(head = tail).
hwq->max_entries will be used to set SQ&CQ size in SQ&CQ Configuration
Registers, we think it should only apply to specific hosts need this
quirk not all.

Thanks,
Chun-Hung

RE: [PATCH v1 0/1] ufs: core: Add host quirk QUIRK_MCQ_EXPAND_QUEUE_SLOT

[Avri Altman]

> Support quirk for host controller not able to distinguish queue full or empty.
> 
> Alice Chao (1):
>   ufs: core: Add host quirk QUIRK_MCQ_EXPAND_QUEUE_SLOT
As part of introducing the quirk, you need to set it on for someone.

Thanks,
Avri

> 
>  drivers/ufs/core/ufs-mcq.c |  5 ++++-
>  include/ufs/ufshcd.h       | 11 +++++++++++
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 
> --
> 2.18.0