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

[Adrian Hunter]

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.

> +		__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.

> +	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);
>  
>