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From:   AceLan Kao <acelan.kao@canonical.com>
Date:   Tue, 8 Oct 2019 11:10:39 +0800
Message-ID: <CAFv23Qmt7BFJgE+=kJFbnJwYDtVrsX56cN6QtZbs=pRwKjbK0Q@mail.gmail.com>
Subject: Re: [PATCH v2] mfd: intel-lpss: use devm_ioremap_uc for MMIO
To:     Tuowen Zhao <ztuowen@gmail.com>
Cc:     Lee Jones <lee.jones@linaro.org>,
        "Linux-Kernel@Vger. Kernel. Org" <linux-kernel@vger.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Kai Heng Feng <kai.heng.feng@canonical.com>,
        "Luis R. Rodriguez" <mcgrof@kernel.org>
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Confirmed the patch works well on Dell XPS 7390 2-in-1 machine.

Tested-by: AceLan Kao <acelan.kao@canonical.com>

Tuowen Zhao <ztuowen@gmail.com> 於 2019年10月8日 週二 上午2:43寫道：
>
> 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)
>
> 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
>