Date:   Tue, 3 Oct 2017 14:44:38 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Vijay Viswanath <vviswana@...eaurora.org>, ulf.hansson@...aro.org,
        will.deacon@....com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        asutoshd@...eaurora.org, stummala@...eaurora.org,
        riteshh@...eaurora.org, subhashj@...eaurora.org
Subject: Re: [PATCH v2 4/4] mmc: sdhci-msm: Add sdhci msm register write APIs
 which wait for pwr irq

On 27/09/17 08:34, Vijay Viswanath wrote:
> Register writes which change voltage of IO lines or turn the IO bus
> on/off require controller to be ready before progressing further. When
> the controller is ready, it will generate a power irq which needs to be
> handled. The thread which initiated the register write should wait for
> power irq to complete. This will be done through the new sdhc msm write
> APIs which will check whether the particular write can trigger a power
> irq and wait for it with a timeout if it is expected.
> The SDHC core power control IRQ gets triggered when -
> * There is a state change in power control bit (bit 0)
>   of SDHCI_POWER_CONTROL register.
> * There is a state change in 1.8V enable bit (bit 3) of
>   SDHCI_HOST_CONTROL2 register.
> * Bit 1 of SDHCI_SOFTWARE_RESET is set.
> 
> Also add support APIs which are used by sdhc msm write APIs to check
> if power irq is expected to be generated and wait for the power irq
> to come and complete if the irq is expected.
> 
> This patch requires CONFIG_MMC_SDHCI_IO_ACCESSORS to be enabled.
> 
> Signed-off-by: Sahitya Tummala <stummala@...eaurora.org>
> Signed-off-by: Vijay Viswanath <vviswana@...eaurora.org>

Acked-by: Adrian Hunter <adrian.hunter@...el.com>

> ---
>  drivers/mmc/host/sdhci-msm.c | 173 ++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 171 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index 42a65ab..b72a487 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 +142,10 @@ struct sdhci_msm_host {
>  	bool calibration_done;
>  	u8 saved_tuning_phase;
>  	bool use_cdclp533;
> +	u32 curr_pwr_state;
> +	u32 curr_io_level;
> +	wait_queue_head_t pwr_irq_wait;
> +	bool pwr_irq_flag;
>  };
>  
>  static unsigned int msm_get_clock_rate_for_bus_mode(struct sdhci_host *host,
> @@ -995,6 +1003,73 @@ static void sdhci_msm_set_uhs_signaling(struct sdhci_host *host,
>  		sdhci_msm_hs400(host, &mmc->ios);
>  }
>  
> +static inline void sdhci_msm_init_pwr_irq_wait(struct sdhci_msm_host *msm_host)
> +{
> +	init_waitqueue_head(&msm_host->pwr_irq_wait);
> +}
> +
> +static inline void sdhci_msm_complete_pwr_irq_wait(
> +		struct sdhci_msm_host *msm_host)
> +{
> +	wake_up(&msm_host->pwr_irq_wait);
> +}
> +
> +/*
> + * 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);
> +	bool done = false;
> +
> +	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, req_type: %d\n",
> +				mmc_hostname(host->mmc), req_type);
> +		return;
> +	}
> +	if ((req_type & msm_host->curr_pwr_state) ||
> +			(req_type & msm_host->curr_io_level))
> +		done = true;
> +	/*
> +	 * This is needed here to handle cases where register writes will
> +	 * not change the current bus state or io level of the controller.
> +	 * In this case, no power irq will be triggerred and we should
> +	 * not wait.
> +	 */
> +	if (!done) {
> +		if (!wait_event_timeout(msm_host->pwr_irq_wait,
> +				msm_host->pwr_irq_flag,
> +				msecs_to_jiffies(MSM_PWR_IRQ_TIMEOUT_MS)))
> +			__WARN_printf("%s: pwr_irq for req: (%d) timed out\n",
> +					mmc_hostname(host->mmc), req_type);
> +	}
> +	pr_debug("%s: %s: request %d done\n", mmc_hostname(host->mmc),
> +			__func__, req_type);
> +}
> +
>  static void sdhci_msm_dump_pwr_ctrl_regs(struct sdhci_host *host)
>  {
>  	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> @@ -1013,6 +1088,8 @@ 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;
> +
>  
>  	irq_status = readl_relaxed(msm_host->core_mem + CORE_PWRCTL_STATUS);
>  	irq_status &= INT_MASK;
> @@ -1041,10 +1118,26 @@ 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
> @@ -1053,6 +1146,11 @@ static void sdhci_msm_handle_pwr_irq(struct sdhci_host *host, int irq)
>  	 */
>  	writel_relaxed(irq_ack, msm_host->core_mem + CORE_PWRCTL_CTL);
>  
> +	if (pwr_state)
> +		msm_host->curr_pwr_state = pwr_state;
> +	if (io_level)
> +		msm_host->curr_io_level = io_level;
> +
>  	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);
> @@ -1061,8 +1159,13 @@ static void sdhci_msm_handle_pwr_irq(struct sdhci_host *host, int irq)
>  static irqreturn_t sdhci_msm_pwr_irq(int irq, void *data)
>  {
>  	struct sdhci_host *host = (struct sdhci_host *)data;
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
>  
>  	sdhci_msm_handle_pwr_irq(host, irq);
> +	msm_host->pwr_irq_flag = 1;
> +	sdhci_msm_complete_pwr_irq_wait(msm_host);
> +
>  
>  	return IRQ_HANDLED;
>  }
> @@ -1131,6 +1234,69 @@ static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
>  	__sdhci_msm_set_clock(host, clock);
>  }
>  
> +/*
> + * Platform specific register write functions. This is so that, if any
> + * register write needs to be followed up by platform specific actions,
> + * they can be added here. These functions can go to sleep when writes
> + * to certain registers are done.
> + * These functions are relying on sdhci_set_ios not using spinlock.
> + */
> +static int __sdhci_msm_check_write(struct sdhci_host *host, u16 val, int reg)
> +{
> +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> +	struct sdhci_msm_host *msm_host = sdhci_pltfm_priv(pltfm_host);
> +	u32 req_type = 0;
> +
> +	switch (reg) {
> +	case SDHCI_HOST_CONTROL2:
> +		req_type = (val & SDHCI_CTRL_VDD_180) ? REQ_IO_LOW :
> +			REQ_IO_HIGH;
> +		break;
> +	case SDHCI_SOFTWARE_RESET:
> +		if (host->pwr && (val & SDHCI_RESET_ALL))
> +			req_type = REQ_BUS_OFF;
> +		break;
> +	case SDHCI_POWER_CONTROL:
> +		req_type = !val ? REQ_BUS_OFF : REQ_BUS_ON;
> +		break;
> +	}
> +
> +	if (req_type) {
> +		msm_host->pwr_irq_flag = 0;
> +		/*
> +		 * Since this register write may trigger a power irq, ensure
> +		 * all previous register writes are complete by this point.
> +		 */
> +		mb();
> +	}
> +	return req_type;
> +}
> +
> +/* This function may sleep*/
> +static void sdhci_msm_writew(struct sdhci_host *host, u16 val, int reg)
> +{
> +	u32 req_type = 0;
> +
> +	req_type = __sdhci_msm_check_write(host, val, reg);
> +	writew_relaxed(val, host->ioaddr + reg);
> +
> +	if (req_type)
> +		sdhci_msm_check_power_status(host, req_type);
> +}
> +
> +/* This function may sleep*/
> +static void sdhci_msm_writeb(struct sdhci_host *host, u8 val, int reg)
> +{
> +	u32 req_type = 0;
> +
> +	req_type = __sdhci_msm_check_write(host, val, reg);
> +
> +	writeb_relaxed(val, host->ioaddr + reg);
> +
> +	if (req_type)
> +		sdhci_msm_check_power_status(host, req_type);
> +}
> +
>  static const struct of_device_id sdhci_msm_dt_match[] = {
>  	{ .compatible = "qcom,sdhci-msm-v4" },
>  	{},
> @@ -1145,6 +1311,8 @@ static void sdhci_msm_set_clock(struct sdhci_host *host, unsigned int clock)
>  	.get_max_clock = sdhci_msm_get_max_clock,
>  	.set_bus_width = sdhci_set_bus_width,
>  	.set_uhs_signaling = sdhci_msm_set_uhs_signaling,
> +	.write_w = sdhci_msm_writew,
> +	.write_b = sdhci_msm_writeb,
>  };
>  
>  static const struct sdhci_pltfm_data sdhci_msm_pdata = {
> @@ -1312,6 +1480,7 @@ static int sdhci_msm_probe(struct platform_device *pdev)
>  		goto clk_disable;
>  	}
>  
> +	sdhci_msm_init_pwr_irq_wait(msm_host);
>  	/* Enable pwr irq interrupts */
>  	writel_relaxed(INT_MASK, msm_host->core_mem + CORE_PWRCTL_MASK);
>  
> 

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