Re: Help needed: Enabling HPI causes some eMMC devices to stop working

[Jaehoon Chung <jh80.chung@samsung.com>]

Hi.

On 02/19/2015 04:15 AM, Hans de Goede wrote:
> Hi,
> 
> As part of the Linux Allwinner SoC support work I do in my
> spare time, I'm working on getting stock Linux running on
> the Utoo P66 Allwinner A13 based tablet.
> 
> This tablet is interesting because it uses an eMMC rather then
> raw nand as is typically seen on Allwinner tablets.
> 
> It has taken me a while to get the kernel to talk to the eMMC,
> in the end the following hack does the trick:
> 
> 
> From: Hans de Goede <hdegoede@redhat.com>
> Date: Wed, 18 Feb 2015 20:04:03 +0100
> Subject: [PATCH] mmc: HACK: disable HPI
> 
> HACK: trying to enable HPI breaks EMMC access on the Utoo P66 tablet I'm
> trying to get supported, so disable it. FIXME: come up with a proper fix.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  drivers/mmc/core/mmc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 1d41e85..b343587 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -1418,7 +1418,7 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
>         /*
>          * Enable HPI feature (if supported)
>          */
> -       if (card->ext_csd.hpi) {
> +       if (0 && card->ext_csd.hpi) {
>                 err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
>                                 EXT_CSD_HPI_MGMT, 1,
>                                 card->ext_csd.generic_cmd6_time);
> 
> This patch has one good thing going for it, which it is that it makes
> the eMMC work, without this talking to the eMMC fails as soon as the
> kernel tries to read the partition table, with response-timeout errors
> when doing a mmc command 18 to read sector 0.

I don't understand what response-timeout error related with HPI?

> 
> So this is as far as I've come, and beyond this my mmc knowledge is simply
> not good enough. Could this be a controller specific problem ? IOW do
> we need a controller flag to not enable HPi, like we've
> MMC_CAP2_BOOTPART_NOACC ? Or is this likely more something specific to the eMMC
> used.
> 
> Assuming for now it is something specific to the eMMC used, how do we fix this?
> 
> Is there maybe some way to figure out that enabling HPI is not a good idea on
> this eMMC?

According to eMMC spec, HPI feature is mandatory. And it only needs to consider how the feature use.
Do you use the BKOPS or other use-case?

Best Regards,
Jaehoon Chung

> 
> Or do we need a quirk for this in devicetree? Now a days we can tie info to an sdio
> slave device in devicetree, so that is an option too.
> 
> Thanks & Regards,
> 
> Hans
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