Re: [PATCH] mmc: sdhci-esdhc-imx: Enable boot partition access from DT

Ulf Hansson
2014-09-03T09:09:07Z

On 3 September 2014 11:02, Adrian Hunter <adrian.hunter@intel.com> wrote:
> On 09/03/2014 11:30 AM, Ulf Hansson wrote:
>> On 2 September 2014 17:49, Jean-Michel Hautbois
>> <jean-michel.hautbois@vodalys.com> wrote:
>>> This property is useful when we don't want to access boot partitions on eMMC
>>>
>>> Signed-off-by: Jean-Michel Hautbois <jean-michel.hautbois@vodalys.com>
>>> ---
>>> Documentation/devicetree/bindings/mmc/mmc.txt | 1 +
>>> drivers/mmc/host/sdhci-esdhc-imx.c | 8 ++++++++
>>> include/linux/platform_data/mmc-esdhc-imx.h | 1 +
>>> 3 files changed, 10 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/mmc/mmc.txt b/Documentation/devicetree/bindings/mmc/mmc.txt
>>> index 431716e..59cc854 100644
>>> --- a/Documentation/devicetree/bindings/mmc/mmc.txt
>>> +++ b/Documentation/devicetree/bindings/mmc/mmc.txt
>>> @@ -40,6 +40,7 @@ Optional properties:
>>> - mmc-hs200-1_2v: eMMC HS200 mode(1.2V I/O) is supported
>>> - mmc-hs400-1_8v: eMMC HS400 mode(1.8V I/O) is supported
>>> - mmc-hs400-1_2v: eMMC HS400 mode(1.2V I/O) is supported
>>> +- no-boot-part : when preset, tells to access boot partitions
>>>
>>> *NOTE* on CD and WP polarity. To use common for all SD/MMC host controllers line
>>> polarity properties, we have to fix the meaning of the "normal" and "inverted"
>>> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
>>> index ccec0e3..439e663 100644
>>> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
>>> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
>>> @@ -942,6 +942,11 @@ sdhci_esdhc_imx_probe_dt(struct platform_device *pdev,
>>> if (of_property_read_u32(np, "fsl,delay-line", &boarddata->delay_line))
>>> boarddata->delay_line = 0;
>>>
>>> + if (of_find_property(np, "no-boot-part", NULL))
>>> + boarddata->access_boot_part = false;
>>> + else
>>> + boarddata->access_boot_part = true;
>>> +
>>> return 0;
>>> }
>>> #else
>>> @@ -1119,6 +1124,9 @@ static int sdhci_esdhc_imx_probe(struct platform_device *pdev)
>>> host->quirks2 |= SDHCI_QUIRK2_NO_1_8_V;
>>> }
>>>
>>> + if (!boarddata->access_boot_part)
>>> + host->mmc->caps2 |= MMC_CAP2_BOOTPART_NOACC;
>>> +
>>
>> Hmm, I don't think MMC_CAP2_BOOTPART_NOACC should have a DT binding.
>> Does it describe the hardware in some form?
>>
>> Actually I would like to question why MMC_CAP2_BOOTPART_NOACC exists
>> at all. If there are cards that don't supports the BOOT area,
>> shouldn't we have a card quirk for it instead of a host cap? Maybe
>> Adrian Hunter, how originally wrote the patch for adding
>> MMC_CAP2_BOOTPART_NOACC, could help me understand the reasons behind
>> it!?
>
> It was added because platform firmware was able to prevent access to the
> boot partitions (for security I think), so attempts to access them would
> fail messily. It was not related to any specific card.

Adrian, appreciate your clarification. After all it seems like adding
a DT binding for it should be appropriate.

Kind regards
Uffe