Message-ID: <57162270.6040701@schinagl.nl>
Date:	Tue, 19 Apr 2016 14:20:00 +0200
From:	Olliver Schinagl <oliver@...inagl.nl>
To:	Jaehoon Chung <jh80.chung@...sung.com>,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Chen-Yu Tsai <wens@...e.org>,
	Venu Byravarasu <vbyravarasu@...dia.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Michal Hocko <mhocko@...e.com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Sudeep Holla <Sudeep.Holla@....com>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	Wolfram Sang <wsa+renesas@...g-engineering.com>,
	Wenkai Du <wenkai.du@...el.com>,
	Chaotian Jing <chaotian.jing@...iatek.com>,
	Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
	Hans de Goede <hdegoede@...hat.com>,
	Michal Suchanek <hramrach@...il.com>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 1/2] mmc: core: Improve marking broken HPI through
 devicetree

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@...inagl.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@...hat.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@...inagl.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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