linux-kernel - Re: [v2] mmc: sdhci-msm: Optionally wait for signal level changes

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Date:   Tue, 21 Nov 2017 20:38:31 +0100
From:   Luca Weiss <luca@...tu.xyz>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, Stephen Boyd <sboyd@...eaurora.org>,
        Sahitya Tummala <stummala@...eaurora.org>,
        Vijay Viswanath <vviswana@...eaurora.org>
Subject: Re: [v2] mmc: sdhci-msm: Optionally wait for signal level changes

On Montag, 20. November 2017 20:56:47 CET Bjorn Andersson wrote:
> Not all instances of the SDCC core supports changing signal voltage and
> as such will not generate a power interrupt when the software attempts
> to change the voltage. This results in probing the eMMC on some devices
> to take over 2 minutes.
> 
> Check that the SWITCHABLE_SIGNALING_VOLTAGE bit in MCI_GENERICS is set
> before waiting for the power interrupt.
> 
> Cc: Sahitya Tummala <stummala@...eaurora.org>
> Cc: Vijay Viswanath <vviswana@...eaurora.org>
> Fixes: c0309b3803fe ("mmc: sdhci-msm: Add sdhci msm register write APIs
> which wait for pwr irq") Signed-off-by: Bjorn Andersson
> <bjorn.andersson@...aro.org>
Tested-by: Luca Weiss <luca@...tu.xyz>
> ---
> 
> The offending patch is part of your v4.15 pull request, so please pick
> this up for the -rcs.
> 
> Changes since v1:
> - Fixed spelling of swichable...
> 
>  drivers/mmc/host/sdhci-msm.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> index 3fb7d2eec93f..c283291db705 100644
> --- a/drivers/mmc/host/sdhci-msm.c
> +++ b/drivers/mmc/host/sdhci-msm.c
> @@ -29,6 +29,9 @@
>  #define CORE_VERSION_MAJOR_MASK		(0xf << CORE_VERSION_MAJOR_SHIFT)
>  #define CORE_VERSION_MINOR_MASK		0xff
> 
> +#define CORE_MCI_GENERICS		0x70
> +#define SWITCHABLE_SIGNALING_VOLTAGE	BIT(29)
> +
>  #define CORE_HC_MODE		0x78
>  #define HC_MODE_EN		0x1
>  #define CORE_POWER		0x0
> @@ -1028,11 +1031,22 @@ 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;
> +	u32 val;
> 
>  	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 power interrupt will not be generated for signal voltage
> +	 * switches if SWITCHABLE_SIGNALING_VOLTAGE in MCI_GENERICS is not set.
> +	 */
> +	val = readl(msm_host->core_mem + CORE_MCI_GENERICS);
> +	if ((req_type & REQ_IO_HIGH || req_type & REQ_IO_LOW) &&
> +	    !(val & SWITCHABLE_SIGNALING_VOLTAGE)) {
> +		return;
> +	}
> +
>  	/*
>  	 * 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