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SubjectRe: [PATCH 1/2] mmc: core: Improve marking broken HPI through devicetree
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Hey Jaehoon,

On 19-04-16 11:49, Jaehoon Chung wrote:
> Hi
>
> On 04/19/2016 06:42 PM, Olliver Schinagl wrote:
>> Hi Ulf,
>>
>> On 19-04-16 11:29, Ulf Hansson wrote:
>>> On 19 April 2016 at 09:12, Olliver Schinagl <oliver@schinagl.nl> wrote:
>>>> In patch 81f8a7be66 Hans de Goede added a patch to allow marking an mmc
>>>> device as to having an broken HPI implementation. After talking some
>>>> with Hans, we now think it is actually the mmc controller that can be
>>>> broken and not support broken HPI's.
>>> I don't want us to invent a DT binding for something you *think* is a
>>> HW controller issue.
>>>
>>> Have you really excluded that this isn't a software issue? Me
>>> personally haven't been using HPI that much so I can't really tell
>>> about the code robustness from the mmc core (mmc protocol point of
>>> view).
>> Well this patch goes hand in hand so to speak with the broken-hpi patch introduced by him, he did most of the investigation. We just discussed how to handle it and asked me to cook up the patch.
> I didn't understand why add this property. Is this same patch?
>
> commit 81f8a7be6642b4c26ab681b2e0f4c4120a6de1b0
> Author: Hans de Goede <hdegoede@redhat.com>
> Date: Wed Apr 1 17:26:23 2015 +0200
>
> mmc: Add support for marking hpi as broken through devicetree
>
> The eMMC on a tablet I've will stop working / communicating as soon as
> the kernel executes:
>
> mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
> EXT_CSD_HPI_MGMT, 1,
> card->ext_csd.generic_cmd6_time);
>
> There seems to be no way to reliable identify eMMC-s which have a broken
> hpi implementation, but at least for eMMC's which are soldered onto a board
> we can work around this by specifying that hpi is broken in devicetree.
Similar, this does it on the card level, e.g. you mark a card as having
a broken HPI implementation.

The truth is, the card may not be broken at all, but the mmc controller
so we add a property on the controller level.

What Ulf is pondering, if this is not a software stack problem, rather
then a hardware implementation, which I don't know.
>> @hans, what do you think?
>>> Kind regards
>>> Uffe
>>>
>>>> This patch adds a new capability, mmc-broken-hpi, which allows us to
>>>> mark a broken hpi implementation on the host level.
>>>>
>>>> Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>
>>>> ---
>>>> drivers/mmc/core/host.c | 2 ++
>>>> drivers/mmc/core/mmc.c | 2 +-
>>>> include/linux/mmc/host.h | 1 +
>>>> 3 files changed, 4 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
>>>> index 6e4c55a..9b63b36 100644
>>>> --- a/drivers/mmc/core/host.c
>>>> +++ b/drivers/mmc/core/host.c
>>>> @@ -270,6 +270,8 @@ int mmc_of_parse(struct mmc_host *host)
>>>> host->caps |= MMC_CAP_HW_RESET;
>>>> if (of_property_read_bool(np, "cap-sdio-irq"))
>>>> host->caps |= MMC_CAP_SDIO_IRQ;
>>>> + if (of_property_read_bool(np, "mmc-broken-hpi"))
>>>> + host->caps |= MMC_CAP_BROKEN_HPI;
>>>> if (of_property_read_bool(np, "full-pwr-cycle"))
>>>> host->caps2 |= MMC_CAP2_FULL_PWR_CYCLE;
>>>> if (of_property_read_bool(np, "keep-power-in-suspend"))
>>>> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
>>>> index 4dbe3df..9a19562 100644
>>>> --- a/drivers/mmc/core/mmc.c
>>>> +++ b/drivers/mmc/core/mmc.c
>>>> @@ -1592,7 +1592,7 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
>>>> /*
>>>> * Enable HPI feature (if supported)
>>>> */
>>>> - if (card->ext_csd.hpi) {
>>>> + if (card->ext_csd.hpi && !(host->caps & MMC_CAP_BROKEN_HPI)) {
>>>> err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
>>>> EXT_CSD_HPI_MGMT, 1,
>>>> card->ext_csd.generic_cmd6_time);
>>>> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
>>>> index 8dd4d29..20f758e 100644
>>>> --- a/include/linux/mmc/host.h
>>>> +++ b/include/linux/mmc/host.h
>>>> @@ -264,6 +264,7 @@ struct mmc_host {
>>>> #define MMC_CAP_DRIVER_TYPE_A (1 << 23) /* Host supports Driver Type A */
>>>> #define MMC_CAP_DRIVER_TYPE_C (1 << 24) /* Host supports Driver Type C */
>>>> #define MMC_CAP_DRIVER_TYPE_D (1 << 25) /* Host supports Driver Type D */
>>>> +#define MMC_CAP_BROKEN_HPI (1 << 29) /* Host support for HPI is broken */
>>>> #define MMC_CAP_CMD23 (1 << 30) /* CMD23 supported. */
>>>> #define MMC_CAP_HW_RESET (1 << 31) /* Hardware reset */
>>>>
>>>> --
>>>> 2.8.0.rc3
>>>>
>>
>>

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