Re: [PATCH 1/4] mmc: mmci: avoid fake busy polling
From: Ludovic BARRE
Date: Thu Apr 25 2019 - 10:09:52 EST
On 4/25/19 12:08 PM, Ulf Hansson wrote:
On Thu, 25 Apr 2019 at 11:22, Ludovic BARRE <ludovic.barre@xxxxxx> wrote:
hi Ulf
On 4/23/19 3:39 PM, Ulf Hansson wrote:
On Tue, 5 Mar 2019 at 17:10, Ludovic Barre <ludovic.Barre@xxxxxx> wrote:
From: Ludovic Barre <ludovic.barre@xxxxxx>
The busy status bit could occurred even if no busy response is
expected (example cmd11). On sdmmc variant, the busy_detect_flag
reflects inverted value of d0 state, it's sampled at the end of a
CMD response and a second time 2 clk cycles after the CMD response.
To avoid a fake busy, the busy status could be checked and polled
only if the command has RSP_BUSY flag.
I would appreciate a better explanation of what this patch really changes.
The above is giving some background to the behavior of sdmmc variant,
but at this point that variant doesn't even have the
->variant->busy_detect flag set.
Yes, I will try to explain more and focus on common behavior.
Signed-off-by: Ludovic Barre <ludovic.barre@xxxxxx>
---
drivers/mmc/host/mmci.c | 19 +++++++++++++------
1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
index 387ff14..4901b73 100644
--- a/drivers/mmc/host/mmci.c
+++ b/drivers/mmc/host/mmci.c
@@ -1220,12 +1220,13 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
unsigned int status)
{
void __iomem *base = host->base;
- bool sbc;
+ bool sbc, busy_resp;
if (!cmd)
return;
sbc = (cmd == host->mrq->sbc);
+ busy_resp = !!(cmd->flags & MMC_RSP_BUSY);
/*
* We need to be one of these interrupts to be considered worth
@@ -1239,8 +1240,7 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
/*
* ST Micro variant: handle busy detection.
*/
- if (host->variant->busy_detect) {
- bool busy_resp = !!(cmd->flags & MMC_RSP_BUSY);
+ if (busy_resp && host->variant->busy_detect) {
/* We are busy with a command, return */
if (host->busy_status &&
@@ -1253,7 +1253,7 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
* that the special busy status bit is still set before
* proceeding.
*/
- if (!host->busy_status && busy_resp &&
+ if (!host->busy_status &&
!(status & (MCI_CMDCRCFAIL|MCI_CMDTIMEOUT)) &&
(readl(base + MMCISTATUS) & host->variant->busy_detect_flag)) {
All the changes above makes perfect sense to me, but looks more like a
cleanup of the code, rather than actually changing the behavior.
yes, few changing (this just avoid to enter in
"if (host->variant->busy_detect)") at each time.
I could move this part in cleanup patch (before this patch)
Sounds good to me!
@@ -1508,6 +1508,7 @@ static irqreturn_t mmci_irq(int irq, void *dev_id)
{
struct mmci_host *host = dev_id;
u32 status;
+ bool busy_resp;
int ret = 0;
spin_lock(&host->lock);
@@ -1550,9 +1551,15 @@ static irqreturn_t mmci_irq(int irq, void *dev_id)
}
/*
- * Don't poll for busy completion in irq context.
+ * Don't poll for:
+ * -busy completion in irq context.
+ * -no busy response expected.
*/
- if (host->variant->busy_detect && host->busy_status)
+ busy_resp = host->cmd ?
+ !!(host->cmd->flags & MMC_RSP_BUSY) : false;
This doesn't make sense to me, but I may be missing something.
host->busy_status is being updated by mmci_cmd_irq() and only when
MMC_RSP_BUSY is set for the command in flight. In other words,
checking for MMC_RSP_BUSY here as well is redundant. No?
In mmci_irq the "do while" loops until the status is totally cleared.
Today (for variant with busy_detect option), the status busy_detect_flag
is excluded only while busy_status period (command with MMC_RSP_BUSY and
while busy line is low => "busy_status=1")
On SDMMC variant I noticed that busy_detect_flag status could be enabled
even if the command is not MMC_RSP_BUSY, for example sdmmc variant stay
in loop while cmd11 voltage switch.
Right, I see.
So I wish extend host->variant->busy_detect_flag exclusion for all
commands which is not a MMC_RSP_BUSY. I suppose that other variants
could have the same behavior, and else there is no impact, normally.
I am guessing this is because the variant->busy_dpsm_flag has been set
in the datactrl register, which is needed for mmci_card_busy().
That said, I am kind of wondering if we ever should need repeat the
while loop if 'status' contains the bit for
host->variant->busy_detect_flag. I mean we have already called
mmci_cmd_irq() to handle it.
So, couldn't we just always do:
if (host->variant->busy_detect_flag)
status &= ~host->variant->busy_detect_flag;
No?
yes that make sense, I launched tests on sdmmc and it's ok.
I think, that we could take on this solution.
If it's ok for you, I resend a series with all modifications.
Regards
Ludo
+
+ if (host->variant->busy_detect &&
+ (!busy_resp || host->busy_status))
status &= ~host->variant->busy_detect_flag;
ret = 1;
--
2.7.4
Kind regards
Uffe
Kind regards
Uffe