Date:   Wed, 18 Jan 2017 14:46:06 +0530
From:   Ritesh Harjani <riteshh@...eaurora.org>
To:     Georgi Djakov <georgi.djakov@...aro.org>
Cc:     adrian.hunter@...el.com, ulf.hansson@...aro.org,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2] mmc: sdhci-msm: Add sdhci_reset() implementation

Hi Georgi,

Sorry for delaying this.
I did check with HW folks here, but it seems like we still don't have 
confirmation. In case if I get any new updates later, we can revisit it.

Also I see that we have the same implementation in current driver for 
changing IO voltage. In that case I think this patch should be fine to 
avoid the error message on reboot.


On 12/3/2016 2:24 PM, Ritesh Harjani wrote:
>
>
> On 12/1/2016 11:38 PM, Georgi Djakov wrote:
>> On 11/29/2016 05:40 AM, Ritesh Harjani wrote:
>>> Hi Georgi,
>>>
>>> On 11/28/2016 11:09 PM, Georgi Djakov wrote:
>>>> On apq8016, apq8084 and apq8074 platforms, writing to the software
>>>> reset register triggers the "power irq". We need to ack and handle
>>>> the irq, otherwise the following message appears:
>>>>
>>>> mmc0: Reset 0x1 never completed.
>>>> sdhci: =========== REGISTER DUMP (mmc0)===========
>>>> sdhci: Sys addr: 0x00000000 | Version:  0x00002e02
>>>> sdhci: Blk size: 0x00004000 | Blk cnt:  0x00000000
>>>> sdhci: Argument: 0x00000000 | Trn mode: 0x00000000
>>>> sdhci: Present:  0x01f80000 | Host ctl: 0x00000000
>>>> sdhci: Power:    0x00000000 | Blk gap:  0x00000000
>>>> sdhci: Wake-up:  0x00000000 | Clock:    0x00000003
>>>> sdhci: Timeout:  0x00000000 | Int stat: 0x00000000
>>>> sdhci: Int enab: 0x00000000 | Sig enab: 0x00000000
>>>> sdhci: AC12 err: 0x00000000 | Slot int: 0x00000000
>>>> sdhci: Caps:     0x322dc8b2 | Caps_1:   0x00008007
>>>> sdhci: Cmd:      0x00000000 | Max curr: 0x00000000
>>>> sdhci: Host ctl2: 0x00000000
>>>> sdhci: ADMA Err: 0x00000000 | ADMA Ptr: 0x0000000000000000
>>>> sdhci: ===========================================
>>>>
>>>> Fix it by implementing the custom sdhci_reset() function,
>>>> which performs the software reset and then handles the irq.
>>>>
>>>> Signed-off-by: Georgi Djakov <georgi.djakov@...aro.org>
>>>> ---
Reviewed-by: Ritesh Harjani <riteshh@...eaurora.org>


>>>>
>>>> Changes since v1: (https://lkml.org/lkml/2016/11/22/411)
>>>>  * Perform the software reset by just writing to the
>>>> SDHCI_SOFTWARE_RESET
>>>>    register and then check for the irq.
>>> I am still not sure about this change. Below change will trigger the
>>> IRQ, once this call is completed (say on a single core system) -since
>>> this is called while holding spin_lock_irqsave.
>>>
>>> But you will be end up calling sdhci_msm_voltage_switch twice,
>>> which to me does not seems correct.
>>> 1. 1st time you are directly calling it in sdhci_msm_reset.
>>> 2. 2nd time will be called from within pwr_irq to handle the same case.
>>
>> Yes, that would be the behavior. This function actually is not doing
>> anything much than to check irq status and ack it. Testing the patch
> Ok.
>
>> on a few different platforms does not show any side effects, however i
>> could not be 100% sure as i have limited information about the hardware.
> what about the case when say the IRQ is delayed because of some other
> overheads in the system. Will this approach still works?
> I understand this would require some HW knowledge to understand the
> functioning/importance of this pwr_irq. I will try and get in touch with
> HW folk here.
>
> Regards
> Ritesh
>
>
>>
>> Thanks,
>> Georgi
>>
>>>
>>> Please let me know your thoughts on this ?
>>>
>>> Regards
>>> Ritesh
>>>
>>>>
>>>>  drivers/mmc/host/sdhci-msm.c | 29 ++++++++++++++++++++++++++++-
>>>>  1 file changed, 28 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/mmc/host/sdhci-msm.c
>>>> b/drivers/mmc/host/sdhci-msm.c
>>>> index 32879b845b75..157ae07f9309 100644
>>>> --- a/drivers/mmc/host/sdhci-msm.c
>>>> +++ b/drivers/mmc/host/sdhci-msm.c
>>>> @@ -1019,6 +1019,33 @@ static void sdhci_msm_set_clock(struct
>>>> sdhci_host *host, unsigned int clock)
>>>>      __sdhci_msm_set_clock(host, clock);
>>>>  }
>>>>
>>>> +void sdhci_msm_reset(struct sdhci_host *host, u8 mask)
>>>> +{
>>>> +    unsigned long timeout = 100;
>>>> +
>>>> +    sdhci_writeb(host, mask, SDHCI_SOFTWARE_RESET);
>>>> +
>>>> +    if (mask & SDHCI_RESET_ALL) {
>>>> +        host->clock = 0;
>>>> +
>>>> +        /*
>>>> +         * SDHCI_RESET_ALL triggers the PWR IRQ and we need
>>>> +         * to handle it here.
>>>> +         */
>>>> +        sdhci_msm_voltage_switch(host);
>>>> +    }
>>>> +
>>>> +    while (sdhci_readb(host, SDHCI_SOFTWARE_RESET) & mask) {
>>>> +        if (timeout == 0) {
>>>> +            pr_err("%s: Reset 0x%x never completed.\n",
>>>> +                   mmc_hostname(host->mmc), (int)mask);
>>>> +            return;
>>>> +        }
>>>> +        timeout--;
>>>> +        mdelay(1);
>>>> +    }
>>>> +}
>>>> +
>>>>  static const struct of_device_id sdhci_msm_dt_match[] = {
>>>>      { .compatible = "qcom,sdhci-msm-v4" },
>>>>      {},
>>>> @@ -1028,7 +1055,7 @@ MODULE_DEVICE_TABLE(of, sdhci_msm_dt_match);
>>>>
>>>>  static const struct sdhci_ops sdhci_msm_ops = {
>>>>      .platform_execute_tuning = sdhci_msm_execute_tuning,
>>>> -    .reset = sdhci_reset,
>>>> +    .reset = sdhci_msm_reset,
>>>>      .set_clock = sdhci_msm_set_clock,
>>>>      .get_min_clock = sdhci_msm_get_min_clock,
>>>>      .get_max_clock = sdhci_msm_get_max_clock,
>>>> --
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>>>>
>>>
>> --
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>

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