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Date:   Tue, 8 Oct 2019 16:58:36 +0300
From:   Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To:     Tuowen Zhao <ztuowen@gmail.com>
Cc:     lee.jones@linaro.org, linux-kernel@vger.kernel.org,
        mika.westerberg@linux.intel.com, acelan.kao@canonical.com,
        bhelgaas@google.com, kai.heng.feng@canonical.com, mcgrof@kernel.org
Subject: Re: [PATCH v2] mfd: intel-lpss: use devm_ioremap_uc for MMIO
Message-ID: <20191008135836.GL32742@smile.fi.intel.com>
References: <20191007184231.13256-1-ztuowen@gmail.com>
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On Mon, Oct 07, 2019 at 12:42:31PM -0600, Tuowen Zhao wrote:
> Some BIOS erroneously specifies write-combining BAR for intel-lpss-pci
> in MTRR. This will cause the system to hang during boot. If possible,
> this bug could be corrected with a firmware update.
> 
> This patch adds devm_ioremap_uc as a new managed wrapper to ioremap_uc
> and with it overwrite the MTRR settings to force the use of strongly
> uncachable pages for intel-lpss.
> 
> The BIOS bug is present on Dell XPS 13 7390 2-in-1:
> 
> [    0.001734]   5 base 4000000000 mask 6000000000 write-combining
> 
> 4000000000-7fffffffff : PCI Bus 0000:00
>   4000000000-400fffffff : 0000:00:02.0 (i915)
>   4010000000-4010000fff : 0000:00:15.0 (intel-lpss-pci)
> 

Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> Link: https://bugzilla.kernel.org/show_bug.cgi?id=203485
> Signed-off-by: Tuowen Zhao <ztuowen@gmail.com>
> ---
> Changes from previous version:
> 
>   * changed commit message
> 
>  drivers/mfd/intel-lpss.c |  2 +-
>  include/linux/io.h       |  2 ++
>  lib/devres.c             | 19 +++++++++++++++++++
>  3 files changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mfd/intel-lpss.c b/drivers/mfd/intel-lpss.c
> index bfe4ff337581..b0f0781a6b9c 100644
> --- a/drivers/mfd/intel-lpss.c
> +++ b/drivers/mfd/intel-lpss.c
> @@ -384,7 +384,7 @@ int intel_lpss_probe(struct device *dev,
>  	if (!lpss)
>  		return -ENOMEM;
>  
> -	lpss->priv = devm_ioremap(dev, info->mem->start + LPSS_PRIV_OFFSET,
> +	lpss->priv = devm_ioremap_uc(dev, info->mem->start + LPSS_PRIV_OFFSET,
>  				  LPSS_PRIV_SIZE);
>  	if (!lpss->priv)
>  		return -ENOMEM;
> diff --git a/include/linux/io.h b/include/linux/io.h
> index accac822336a..a59834bc0a11 100644
> --- a/include/linux/io.h
> +++ b/include/linux/io.h
> @@ -64,6 +64,8 @@ static inline void devm_ioport_unmap(struct device *dev, void __iomem *addr)
>  
>  void __iomem *devm_ioremap(struct device *dev, resource_size_t offset,
>  			   resource_size_t size);
> +void __iomem *devm_ioremap_uc(struct device *dev, resource_size_t offset,
> +				   resource_size_t size);
>  void __iomem *devm_ioremap_nocache(struct device *dev, resource_size_t offset,
>  				   resource_size_t size);
>  void __iomem *devm_ioremap_wc(struct device *dev, resource_size_t offset,
> diff --git a/lib/devres.c b/lib/devres.c
> index 6a0e9bd6524a..beb0a064b891 100644
> --- a/lib/devres.c
> +++ b/lib/devres.c
> @@ -9,6 +9,7 @@
>  enum devm_ioremap_type {
>  	DEVM_IOREMAP = 0,
>  	DEVM_IOREMAP_NC,
> +	DEVM_IOREMAP_UC,
>  	DEVM_IOREMAP_WC,
>  };
>  
> @@ -39,6 +40,9 @@ static void __iomem *__devm_ioremap(struct device *dev, resource_size_t offset,
>  	case DEVM_IOREMAP_NC:
>  		addr = ioremap_nocache(offset, size);
>  		break;
> +	case DEVM_IOREMAP_UC:
> +		addr = ioremap_uc(offset, size);
> +		break;
>  	case DEVM_IOREMAP_WC:
>  		addr = ioremap_wc(offset, size);
>  		break;
> @@ -68,6 +72,21 @@ void __iomem *devm_ioremap(struct device *dev, resource_size_t offset,
>  }
>  EXPORT_SYMBOL(devm_ioremap);
>  
> +/**
> + * devm_ioremap_uc - Managed ioremap_uc()
> + * @dev: Generic device to remap IO address for
> + * @offset: Resource address to map
> + * @size: Size of map
> + *
> + * Managed ioremap_uc().  Map is automatically unmapped on driver detach.
> + */
> +void __iomem *devm_ioremap_uc(struct device *dev, resource_size_t offset,
> +			      resource_size_t size)
> +{
> +	return __devm_ioremap(dev, offset, size, DEVM_IOREMAP_UC);
> +}
> +EXPORT_SYMBOL(devm_ioremap_uc);
> +
>  /**
>   * devm_ioremap_nocache - Managed ioremap_nocache()
>   * @dev: Generic device to remap IO address for
> -- 
> 2.23.0
> 

-- 
With Best Regards,
Andy Shevchenko