Re: [PATCH 3/5] mmc: sdhci-msm: Add support to wait for power irq

From: Vijay Viswanath
Date: Mon Aug 28 2017 - 08:35:02 EST

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In reply to: Adrian Hunter: "Re: [PATCH 3/5] mmc: sdhci-msm: Add support to wait for power irq"
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On 8/24/2017 3:35 PM, Adrian Hunter wrote:

On 18/08/17 08:19, Vijay Viswanath wrote:

From: Sahitya Tummala <stummala@xxxxxxxxxxxxxx>

Add support API which will check if power irq is expected to be
generated and wait for the power irq to come and complete if the irq is
expected.

Signed-off-by: Sahitya Tummala <stummala@xxxxxxxxxxxxxx>
Signed-off-by: Vijay Viswanath <vviswana@xxxxxxxxxxxxxx>
---
drivers/mmc/host/sdhci-msm.c | 125 ++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 123 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
index f3e0489..6d3b1fd 100644
--- a/drivers/mmc/host/sdhci-msm.c
+++ b/drivers/mmc/host/sdhci-msm.c
@@ -123,6 +123,10 @@
#define CMUX_SHIFT_PHASE_MASK (7 << CMUX_SHIFT_PHASE_SHIFT)
#define MSM_MMC_AUTOSUSPEND_DELAY_MS 50
+
+/* Timeout value to avoid infinite waiting for pwr_irq */
+#define MSM_PWR_IRQ_TIMEOUT_MS 5000
+
struct sdhci_msm_host {
struct platform_device *pdev;
void __iomem *core_mem; /* MSM SDCC mapped address */
@@ -138,6 +142,11 @@ struct sdhci_msm_host {
bool calibration_done;
u8 saved_tuning_phase;
bool use_cdclp533;
+ u32 curr_pwr_state;
+ u32 curr_io_level;
+#ifdef CONFIG_MMC_SDHCI_IO_ACCESSORS
+ struct completion pwr_irq_completion;
+#endif
};
static unsigned int msm_get_clock_rate_for_bus_mode(struct sdhci_host *host,
@@ -995,6 +1004,90 @@ static void sdhci_msm_set_uhs_signaling(struct sdhci_host *host,
sdhci_msm_hs400(host, &mmc->ios);
}
+#ifdef CONFIG_MMC_SDHCI_IO_ACCESSORS
+static inline void sdhci_msm_init_pwr_irq_completion(
+ struct sdhci_msm_host *msm_host)
+{
+ init_completion(&msm_host->pwr_irq_completion);
+}
+
+static inline void sdhci_msm_complete_pwr_irq_completion(
+ struct sdhci_msm_host *msm_host)
+{
+ complete(&msm_host->pwr_irq_completion);
+}
+
+/*
+ * sdhci_msm_check_power_status API should be called when registers writes
+ * which can toggle sdhci IO bus ON/OFF or change IO lines HIGH/LOW happens.
+ * To what state the register writes will change the IO lines should be passed
+ * as the argument req_type. This API will check whether the IO line's state
+ * is already the expected state and will wait for power irq only if
+ * power irq is expected to be trigerred based on the current IO line state
+ * and expected IO line state.
+ */
+static void sdhci_msm_check_power_status(struct sdhci_host *host, u32 req_type)
+{
+ struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+ struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
+ unsigned long flags;
+ bool done = false;
+
+ spin_lock_irqsave(&host->lock, flags);
+ pr_debug("%s: %s: request %d curr_pwr_state %x curr_io_level %x\n",
+ mmc_hostname(host->mmc), __func__, req_type,
+ msm_host->curr_pwr_state, msm_host->curr_io_level);
+
+ /*
+ * The IRQ for request type IO High/LOW will be generated when -
+ * there is a state change in 1.8V enable bit (bit 3) of
+ * SDHCI_HOST_CONTROL2 register. The reset state of that bit is 0
+ * which indicates 3.3V IO voltage. So, when MMC core layer tries
+ * to set it to 3.3V before card detection happens, the
+ * IRQ doesn't get triggered as there is no state change in this bit.
+ * The driver already handles this case by changing the IO voltage
+ * level to high as part of controller power up sequence. Hence, check
+ * for host->pwr to handle a case where IO voltage high request is
+ * issued even before controller power up.
+ */
+ if ((req_type & REQ_IO_HIGH) && !host->pwr) {
+ pr_debug("%s: do not wait for power IRQ that never comes\n",
+ mmc_hostname(host->mmc));
+ spin_unlock_irqrestore(&host->lock, flags);
+ return;
+ }
+ if ((req_type & msm_host->curr_pwr_state) ||
+ (req_type & msm_host->curr_io_level))
+ done = true;
+ spin_unlock_irqrestore(&host->lock, flags);
+ /*
+ * This is needed here to hanlde a case where IRQ gets
+ * triggered even before this function is called so that
+ * x->done counter of completion gets reset. Otherwise,
+ * next call to wait_for_completion returns immediately
+ * without actually waiting for the IRQ to be handled.
+ */
+ if (done)
+ init_completion(&msm_host->pwr_irq_completion);
+ else if (!wait_for_completion_timeout(&msm_host->pwr_irq_completion,
+ msecs_to_jiffies(MSM_PWR_IRQ_TIMEOUT_MS)))

This all looks a bit more complicated and fragile than it needs to be. You
are waiting for an event so you really want to be using
wait_event_timeout(). Reset the event condition before (will need a memory
barrier) writing the register and then just wait_event_timeout() to wait i.e.

Waiter:
clear flag
memory barrier
write register
wait_event_timeout(wq,flag is set,timeout)

Interrupt:
set flag
wake_up(&wq);

AFAICS you shouldn't need the spin lock at all.

Will do it this way. It looks cleaner and neat. Thanks!

+ __WARN_printf("%s: request(%d) timed out waiting for pwr_irq\n",
+ mmc_hostname(host->mmc), req_type);
+ pr_debug("%s: %s: request %d done\n", mmc_hostname(host->mmc),
+ __func__, req_type);
+}
+#else
+static inline void sdhci_msm_init_pwr_irq_completion(
+ struct sdhci_msm_host *msm_host)
+{
+}
+
+static inline void sdhci_msm_complete_pwr_irq_completion(
+ struct sdhci_msm_host *msm_host)
+{
+}
+#endif
+
static void sdhci_msm_dump_pwr_ctrl_regs(struct sdhci_host *host)
{
struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
@@ -1013,6 +1106,9 @@ static void sdhci_msm_handle_pwr_irq(struct sdhci_host *host, int irq)
struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
u32 irq_status, irq_ack = 0;
int retry = 10;
+ int pwr_state = 0, io_level = 0;
+ unsigned long flags;
+
irq_status = readl_relaxed(msm_host->core_mem + CORE_PWRCTL_STATUS);
irq_status &= INT_MASK;
@@ -1040,10 +1136,26 @@ static void sdhci_msm_handle_pwr_irq(struct sdhci_host *host, int irq)
udelay(10);
}
- if (irq_status & (CORE_PWRCTL_BUS_ON | CORE_PWRCTL_BUS_OFF))
+ /* Handle BUS ON/OFF*/
+ if (irq_status & CORE_PWRCTL_BUS_ON) {
+ pwr_state = REQ_BUS_ON;
+ io_level = REQ_IO_HIGH;
+ irq_ack |= CORE_PWRCTL_BUS_SUCCESS;
+ }
+ if (irq_status & CORE_PWRCTL_BUS_OFF) {
+ pwr_state = REQ_BUS_OFF;
+ io_level = REQ_IO_LOW;
irq_ack |= CORE_PWRCTL_BUS_SUCCESS;
- if (irq_status & (CORE_PWRCTL_IO_LOW | CORE_PWRCTL_IO_HIGH))
+ }
+ /* Handle IO LOW/HIGH */
+ if (irq_status & CORE_PWRCTL_IO_LOW) {
+ io_level = REQ_IO_LOW;
irq_ack |= CORE_PWRCTL_IO_SUCCESS;
+ }
+ if (irq_status & CORE_PWRCTL_IO_HIGH) {
+ io_level = REQ_IO_HIGH;
+ irq_ack |= CORE_PWRCTL_IO_SUCCESS;
+ }
/*
* The driver has to acknowledge the interrupt, switch voltages and
@@ -1052,6 +1164,14 @@ static void sdhci_msm_handle_pwr_irq(struct sdhci_host *host, int irq)
*/
writel_relaxed(irq_ack, msm_host->core_mem + CORE_PWRCTL_CTL);
+ spin_lock_irqsave(&host->lock, flags);
+ if (pwr_state)
+ msm_host->curr_pwr_state = pwr_state;
+ if (io_level)
+ msm_host->curr_io_level = io_level;

Why separate curr_pwr_state and curr_io_level - the bits are separate
anyway. Looks like this could just be:

if (irq_status & (CORE_PWRCTL_BUS_ON | CORE_PWRCTL_BUS_OFF))
irq_ack |= CORE_PWRCTL_BUS_SUCCESS;
if (irq_status & (CORE_PWRCTL_IO_LOW | CORE_PWRCTL_IO_HIGH))
irq_ack |= CORE_PWRCTL_IO_SUCCESS;
writel_relaxed(irq_ack, msm_host->core_mem + CORE_PWRCTL_CTL);

msm_host->pwr_irq_status = irq_status;

And as mentioned above, I don't think you need the spin lock.

I will remove the spinlock. Regarding why there are separate variable for BUS state and IO level,
During initialization, we get CORE_PWRCTL_BUS_ON interrupt from PWRCTL register. But the bit CORE_PWRCTL_IO_HIGH will not be set in the CORE_PWRCTL_STATUS register even though the io level will be high. So after the BUS is set on, if we do a register write to set IO as high, in the sdhci_msm_check_power_status register, we will think that there is a change in IO level and will wait for power irq . But the controller will not trigger any power irq as the IO level was already high.
So whenever we get the BUS_ON interrupt, we should store somewhere that the IO level is also HIGH.

We can do the above with a single variable instead of 2 variables used now, but it will make the code more complex. Whenever we have to change the pwr_irq_status in msm_host, we will have to clear either the 2 IO bits or the whole variable when we get power irq for IO level change or BUS on/off respectively.

+ spin_unlock_irqrestore(&host->lock, flags);
+ sdhci_msm_complete_pwr_irq_completion(msm_host);
+
pr_debug("%s: %s: Handled IRQ(%d), irq_status=0x%x, ack=0x%x\n",
mmc_hostname(msm_host->mmc), __func__, irq, irq_status,
irq_ack);
@@ -1319,6 +1439,7 @@ static int sdhci_msm_probe(struct platform_device *pdev)
goto clk_disable;
}
+ sdhci_msm_init_pwr_irq_completion(msm_host);
/* Enable pwr irq interrupts */
writel_relaxed(INT_MASK, msm_host->core_mem + CORE_PWRCTL_MASK);

Next message: Vijay Viswanath: "Re: [PATCH 4/5] mmc: sdhci-msm: Add ops to do sdhc register write"
Previous message: Masahiro Yamada: "[PATCH] arm64: dts: uniphier: add PXs3 SoC support"
In reply to: Adrian Hunter: "Re: [PATCH 3/5] mmc: sdhci-msm: Add support to wait for power irq"
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