linux-kernel - Re: [PATCH 2/3] sdhci: sparx5: Add Sparx5 SoC eMMC driver

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Message-ID: <87k10uq19i.fsf@soft-dev15.microsemi.net>
Date:   Fri, 29 May 2020 16:11:37 +0200
From:   Lars Povlsen <lars.povlsen@...rochip.com>
To:     Adrian Hunter <adrian.hunter@...el.com>
CC:     Ulf Hansson <ulf.hansson@...aro.org>, SoC Team <soc@...nel.org>,
        "Microchip Linux Driver Support" <UNGLinuxDriver@...rochip.com>,
        <linux-mmc@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>
Subject: Re: [PATCH 2/3] sdhci: sparx5: Add Sparx5 SoC eMMC driver


Lars Povlsen writes:

> Adrian Hunter writes:
>
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>
>> On 20/05/20 2:14 pm, Lars Povlsen wrote:
>>>
>>> Lars Povlsen writes:
>>>
>>>> Adrian Hunter writes:
>>>>
>>>>> On 13/05/20 4:31 pm, Lars Povlsen wrote:
>>>>>> This adds the eMMC driver for the Sparx5 SoC. It is based upon the
>>>>>> designware IP, but requires some extra initialization and quirks.
>>>>>>
>>>>>> Reviewed-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
>>>>>> Signed-off-by: Lars Povlsen <lars.povlsen@...rochip.com>
>>>>>> ---
>>> {Snip]
>>>>>> +};
>>>>>> +
>>>>>> +static const struct sdhci_pltfm_data sdhci_sparx5_pdata = {
>>>>>> +     .quirks  = 0,
>>>>>> +     .quirks2 = SDHCI_QUIRK2_HOST_NO_CMD23 | /* Card quirk */
>>>>>
>>>>> If this is a card quirk then it should be in drivers/mmc/core/quirks.h not here.
>>>>
>>>
>>> Adrian, I had a go at changing the controller quirk to a card quirk.
>>>
>>> Unfortunately, SDHCI_QUIRK2_HOST_NO_CMD23 does not directly translate to
>>> MMC_QUIRK_BLK_NO_CMD23, as for 'do_rel_wr' in mmc_blk_rw_rq_prep(), it
>>> will *still* use MMC_SET_BLOCK_COUNT (cmd23), causing the issue.
>>>
>>> We are using a ISSI "IS004G" device, and so I have gone through the
>>> motions of adding it to quirks.h. The comment before the list of devices
>>> using MMC_QUIRK_BLK_NO_CMD23 suggest working around a performance issue,
>>> which is not exactly the issue I'm seeing. I'm seeing combinations of
>>> CMD_TOUT_ERR, DATA_CRC_ERR and DATA_END_BIT_ERR whenever a cmd23 is
>>> issued.
>>>
>>> I have not been able to test the controller with another eMMC device
>>> yet, but I expect its not the controller at fault.
>>>
>>> So, I'm a little bit in doubt of how to proceed - either keep the quirk
>>> as a controller quirk - or make a *new* card quirk (with
>>> SDHCI_QUIRK2_HOST_NO_CMD23 semantics)?
>>>
>>> Anybody else have had experience with ISSI eMMC devices?
>>>
>>> I have also tried to use DT sdhci-caps-mask, but MMC_CAP_CMD23 is not
>>> read from the controller just (unconditionally) set in sdhci.c - so that
>>> doesn't fly either.
>>>
>>> Any suggestions?
>>
>> It is up to you.  In the future, you may want to distinguish devices that
>> have this problem from ones that do not.
>>
>> If you are not sure it is the ISSI eMMC, and maybe not the host controller,
>> then might it be the board?  Perhaps make SDHCI_QUIRK2_HOST_NO_CMD23
>> conditional on the particular compatibility string?
>>
>> At a minimum, change the "/* Card quirk */" comment to a fuller explanation.
>>
>
> Adrian, I'm getting a board ready with another eMMC device, and we're
> also trying to contact ISSI for info.
>
> My hope is to at least verify whether this is a controller or a card
> issue one way or the other. Then, I'll choose an appropriate solution
> for it.
>
> Thank you for your advice so far.
>

I was able to try on a board with another eMMC card (panasonic), so that
clearly casts the suspicion on the controller, and ISSI is in the clear.

I reintroduced the original SDHCI_QUIRK2_HOST_NO_CMD23 quirk, with a
"Controller issue" comment.

I will refresh the series shortly.

Cheers,

> ---Lars
>
>>>
>>>> Yes, its supposedly a card quirk. I'll see to use the card quirks
>>>> methods in place.
>>>>
>>>

--
Lars Povlsen,
Microchip