linux-kernel - Re: [PATCH v4 2/4] mmc: dw_mmc: Add exynos resume_noirq callback to clear WAKEUP

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Message-ID: <19655139.gpQFe0oLNI@flatron>
Date:	Tue, 06 Aug 2013 23:58:13 +0200
From:	Tomasz Figa <tomasz.figa@...il.com>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Chris Ball <cjb@...top.org>, Olof Johansson <olof@...om.net>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	James Hogan <james.hogan@...tec.com>,
	Grant Grundler <grundler@...omium.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	Abhilash Kesavan <a.kesavan@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>, linux-mmc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/4] mmc: dw_mmc: Add exynos resume_noirq callback to clear WAKEUP_INT

Hi Doug,

See my comment inline.

On Tuesday 06 of August 2013 14:37:49 Doug Anderson wrote:
> If the WAKEUP_INT is asserted at wakeup and not cleared, we'll end up
> looping around forever.  This has been seen to happen on exynos5420
> silicon despite the fact that we haven't enabled any wakeup events due
> to a silicon errata.  It is safe to do on all exynos variants.
> 
> Signed-off-by: Doug Anderson <dianders@...omium.org>
> ---
> Changes in v4:
> - Take Seungwon's suggestion and don't add any dw_mmc-pltfm code.
> 
> Changes in v3:
> - Add freeze/thaw and poweroff/restore noirq entries.
> 
> Changes in v2:
> - Use suspend_noirq as per James Hogan.
> 
>  drivers/mmc/host/dw_mmc-exynos.c | 51
> ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 49
> insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mmc/host/dw_mmc-exynos.c
> b/drivers/mmc/host/dw_mmc-exynos.c index 866edef..0c1f192 100644
> --- a/drivers/mmc/host/dw_mmc-exynos.c
> +++ b/drivers/mmc/host/dw_mmc-exynos.c
> @@ -30,6 +30,7 @@
>  #define SDMMC_CLKSEL_TIMING(x, y, z)	(SDMMC_CLKSEL_CCLK_SAMPLE(x) |	\
>  					SDMMC_CLKSEL_CCLK_DRIVE(y) |	\
>  					SDMMC_CLKSEL_CCLK_DIVIDER(z))
> +#define SDMMC_CLKSEL_WAKEUP_INT		BIT(11)
> 
>  #define EXYNOS4210_FIXED_CIU_CLK_DIV	2
>  #define EXYNOS4412_FIXED_CIU_CLK_DIV	4
> @@ -100,6 +101,30 @@ static int dw_mci_exynos_setup_clock(struct dw_mci
> *host) return 0;
>  }
> 
> +/**
> + * dw_mci_exynos_resume_noirq - Exynos-specific resume code
> + *
> + * On exynos5420 there is a silicon errata that will sometimes leave
> the + * WAKEUP_INT bit in the CLKSEL register asserted.  This bit is 1
> to indicate + * that it fired and we can clear it by writing a 1 back. 
> Clear it to prevent + * interrupts from going off constantly.
> + *
> + * We run this code on all exynos variants because it doesn't hurt and
> the bug + * may be more widespread than just exynos5420.
> + */
> +
> +static int dw_mci_exynos_resume_noirq(struct device *dev)
> +{
> +	struct dw_mci *host = dev_get_drvdata(dev);
> +	u32 clksel;
> +
> +	clksel = mci_readl(host, CLKSEL);
> +	if (clksel & SDMMC_CLKSEL_WAKEUP_INT)
> +		mci_writel(host, CLKSEL, clksel);

What about clock gating? Will the clock used for clocking this register be 
always enabled when this gets called?

Best regards,
Tomasz

> +	return 0;
> +}
> +
>  static void dw_mci_exynos_prepare_command(struct dw_mci *host, u32
> *cmdr) {
>  	/*
> @@ -187,17 +212,39 @@ static int dw_mci_exynos_probe(struct
> platform_device *pdev) return dw_mci_pltfm_register(pdev, drv_data);
>  }
> 
> +static struct dev_pm_ops dw_mci_exynos_pmops;
> +
>  static struct platform_driver dw_mci_exynos_pltfm_driver = {
>  	.probe		= dw_mci_exynos_probe,
>  	.remove		= __exit_p(dw_mci_pltfm_remove),
>  	.driver		= {
>  		.name		= "dwmmc_exynos",
>  		.of_match_table	= dw_mci_exynos_match,
> -		.pm		= &dw_mci_pltfm_pmops,
> +		.pm		= &dw_mci_exynos_pmops,
>  	},
>  };
> 
> -module_platform_driver(dw_mci_exynos_pltfm_driver);
> +static int __init dw_mci_exynos_init(void)
> +{
> +	/* Add a "noirq" resume to platform pmops */
> +	memcpy(&dw_mci_exynos_pmops, &dw_mci_pltfm_pmops,
> +	       sizeof(dw_mci_exynos_pmops));
> +	WARN_ON(dw_mci_exynos_pmops.resume_noirq ||
> +		dw_mci_exynos_pmops.thaw_noirq ||
> +		dw_mci_exynos_pmops.restore_noirq);
> +	dw_mci_exynos_pmops.resume_noirq = dw_mci_exynos_resume_noirq;
> +	dw_mci_exynos_pmops.thaw_noirq = dw_mci_exynos_resume_noirq;
> +	dw_mci_exynos_pmops.restore_noirq = dw_mci_exynos_resume_noirq;
> +
> +	return platform_driver_register(&dw_mci_exynos_pltfm_driver);
> +}
> +module_init(dw_mci_exynos_init);
> +
> +static void __exit dw_mci_exynos_exit(void)
> +{
> +	platform_driver_unregister(&dw_mci_exynos_pltfm_driver);
> +}
> +module_exit(dw_mci_exynos_exit);
> 
>  MODULE_DESCRIPTION("Samsung Specific DW-MSHC Driver Extension");
>  MODULE_AUTHOR("Thomas Abraham <thomas.ab@...sung.com");
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