This refactors the ->busy_complete() callback currently
only used by Ux500 and STM32 to handle busy detection on
hardware where one and the same IRQ is fired whether we get
a start or an end signal on busy detect.
The code is currently using the cached status from the
command IRQ in ->busy_status as a state to select what to
do next: if this state is non-zero we are waiting for
IRQs and if it is zero we treat the state as the starting
point for a busy detect wait cycle.
Make this explicit by creating a state machine where the
->busy_complete callback moves between three states.
The Ux500 busy detect code currently assumes this order:
we enable the busy detect IRQ, get a busy start IRQ, then a
busy end IRQ, and then we clear and mask this IRQ and
proceed.
We insert debug prints for unexpected states.
This works as before on most cards, however on a
problematic card that is not working with busy detect, and
which I have been debugging, the following happens a lot:
[ 3.380554] mmci-pl18x 80005000.mmc: no busy signalling in time
[ 3.387420] mmci-pl18x 80005000.mmc: no busy signalling in time
[ 3.394561] mmci-pl18x 80005000.mmc: lost busy status
when waiting for busy start IRQ
This probably means that the busy detect start IRQ has
already occurred when we start executing the
->busy_complete() callbacks, and the busy detect end IRQ
is counted as the start IRQ, and this is what is causing
the card to not be detected properly.
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
---
ChangeLog v6->v7:
- Return properly with true if we get the second "busy end IRQ"
as expected.
- If busy is still asserted at busy end IRQ, we keep waiting
instead of aborting and completing the command.
- Drop the STM32 changes - just makes things complex.
ChangeLog v4->v6:
- When waiting for the busy end IRQ, what we expect is that
the IRQ should trigger right after the busy signal ends, and
thus thes busy indication should be de-asserted (low). We
invert the logic such that this is what we expect, and
the error case is if the busy detect status is still high
when we get the busy end IRQ.
ChangeLog v3->v4:
- Assign state MMCI_BUSY_DONE outside the if()-clause for
the busy detect initialization.
ChangeLog v2->v3:
- Drop surplus states and merge IDLE and DONE states into one,
we start out DONE. Name states *_WAITING_FOR_* so it is clear
what is going on.
- Rebase on other changes.
- Reword commit message.
ChangeLog v1->v2:
- No changes
---
drivers/mmc/host/mmci.c | 49 +++++++++++++++++++++++++++++++------------------
drivers/mmc/host/mmci.h | 14 ++++++++++++++
2 files changed, 45 insertions(+), 18 deletions(-)
diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
index e493fb7c724f..e61aeca278ec 100644
--- a/drivers/mmc/host/mmci.c
+++ b/drivers/mmc/host/mmci.c
@@ -680,6 +680,7 @@ static bool ux500_busy_complete(struct mmci_host *host, u32 status, u32 err_msk)
writel(host->variant->busy_detect_mask, base + MMCICLEAR);
writel(readl(base + MMCIMASK0) &
~host->variant->busy_detect_mask, base + MMCIMASK0);
+ host->busy_state = MMCI_BUSY_DONE;
host->busy_status = 0;
return true;
}
@@ -697,7 +698,7 @@ static bool ux500_busy_complete(struct mmci_host *host, u32 status, u32 err_msk)
* while, to allow it to be set, but tests indicates that it
* isn't needed.
*/
- if (!host->busy_status) {
+ if (host->busy_state == MMCI_BUSY_DONE) {
status = readl(base + MMCISTATUS);
if (status & host->variant->busy_detect_flag) {
writel(readl(base + MMCIMASK0) |
@@ -705,6 +706,7 @@ static bool ux500_busy_complete(struct mmci_host *host, u32 status, u32 err_msk)
base + MMCIMASK0);
host->busy_status = status & (MCI_CMDSENT | MCI_CMDRESPEND);
+ host->busy_state = MMCI_BUSY_WAITING_FOR_START_IRQ;
return false;
}
}
@@ -720,25 +722,34 @@ static bool ux500_busy_complete(struct mmci_host *host, u32 status, u32 err_msk)
* both the start and the end interrupts needs to be cleared,
* one after the other. So, clear the busy start IRQ here.
*/
- if (host->busy_status &&
- (status & host->variant->busy_detect_flag)) {
- host->busy_status |= status & (MCI_CMDSENT | MCI_CMDRESPEND);
- writel(host->variant->busy_detect_mask, base + MMCICLEAR);
- return false;
+ if (host->busy_state == MMCI_BUSY_WAITING_FOR_START_IRQ) {
+ if (status & host->variant->busy_detect_flag) {
+ host->busy_status |= status & (MCI_CMDSENT | MCI_CMDRESPEND);
+ writel(host->variant->busy_detect_mask, base + MMCICLEAR);
+ host->busy_state = MMCI_BUSY_WAITING_FOR_END_IRQ;
+ return false;
+ } else {
+ dev_dbg(mmc_dev(host->mmc),
+ "lost busy status when waiting for busy start IRQ\n");
+ writel(host->variant->busy_detect_mask, base + MMCICLEAR);
+ writel(readl(base + MMCIMASK0) &
+ ~host->variant->busy_detect_mask, base + MMCIMASK0);
+ host->busy_state = MMCI_BUSY_DONE;
+ host->busy_status = 0;
+ return true;
+ }
}
- /*
- * If there is a command in-progress that has been successfully
- * sent and the busy bit isn't set, it means we have received
- * the busy end IRQ. Clear and mask the IRQ, then continue to
- * process the command.
- */
- if (host->busy_status) {
- writel(host->variant->busy_detect_mask, base + MMCICLEAR);
-
- writel(readl(base + MMCIMASK0) &
- ~host->variant->busy_detect_mask, base + MMCIMASK0);
- host->busy_status = 0;
+ if (host->busy_state == MMCI_BUSY_WAITING_FOR_END_IRQ) {
+ if (!(status & host->variant->busy_detect_flag)) {
+ host->busy_status |= status & (MCI_CMDSENT | MCI_CMDRESPEND);
+ host->busy_state = MMCI_BUSY_DONE;
+ return true;
+ } else {
+ dev_dbg(mmc_dev(host->mmc),
+ "busy status still asserted when handling busy end IRQ - will keep waiting\n");
+ return false;
+ }
}
return true;
@@ -1268,6 +1279,8 @@ mmci_start_command(struct mmci_host *host, struct mmc_command *cmd, u32 c)
}
host->busy_status = 0;
+ host->busy_state = MMCI_BUSY_DONE;
+
if (host->variant->busy_timeout && cmd->flags & MMC_RSP_BUSY) {
if (!cmd->busy_timeout)
cmd->busy_timeout = 10 * MSEC_PER_SEC;
diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
index e1a9b96a3396..12a7bbd3ce26 100644
--- a/drivers/mmc/host/mmci.h
+++ b/drivers/mmc/host/mmci.h
@@ -261,6 +261,19 @@ struct clk;
struct dma_chan;
struct mmci_host;
+/**
+ * enum mmci_busy_state - enumerate the busy detect wait states
+ *
+ * This is used for the state machine waiting for different busy detect
+ * interrupts on hardware that fire a single IRQ for start and end of
+ * the busy detect phase on DAT0.
+ */
+enum mmci_busy_state {
+ MMCI_BUSY_WAITING_FOR_START_IRQ,
+ MMCI_BUSY_WAITING_FOR_END_IRQ,
+ MMCI_BUSY_DONE,
+};
+
/**
* struct variant_data - MMCI variant-specific quirks
* @clkreg: default value for MCICLOCK register
@@ -409,6 +422,7 @@ struct mmci_host {
u32 clk_reg;
u32 clk_reg_add;
u32 datactrl_reg;
+ enum mmci_busy_state busy_state;
u32 busy_status;
u32 mask1_reg;
u8 vqmmc_enabled:1;
--
2.40.1
