linux-kernel - Re: [PATCH v4] mmc: dw_mmc: force setup bus if active slots exist

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Message-ID: <ba42b6c0-067a-ea3d-8330-c2b6ee7a9c36@rock-chips.com>
Date:   Mon, 9 Jan 2017 14:40:10 +0800
From:   Shawn Lin <shawn.lin@...k-chips.com>
To:     Jaehoon Chung <jh80.chung@...sung.com>,
        Ziyuan <xzy.xu@...k-chips.com>, ulf.hansson@...aro.org
Cc:     shawn.lin@...k-chips.com, randy.li@...k-chips.com,
        linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v4] mmc: dw_mmc: force setup bus if active slots exist

On 2017/1/9 13:41, Jaehoon Chung wrote:
> On 01/09/2017 12:39 PM, Ziyuan wrote:
>>
>>
>> On 01/05/2017 03:34 PM, Shawn Lin wrote:
>>> On 2017/1/5 15:23, Ziyuan Xu wrote:
>>>> It's necessary to setup bus if any slots are present.
>>>> - update clock after ctrl reset
>>>> - if the host has genpd node, we can guarantee the clock is available
>>>> before starting request. Otherwies, the clock register is reset once
>>>> power off the pd, and host can't output the active clock during
>>>> communication.
>>>>
>>>> fixes: e9ed8835e990 ("mmc: dw_mmc: add runtime PM callback")
>>>> Reported-by: Randy Li <randy.li@...k-chips.com>
>>>> Signed-off-by: Ziyuan Xu <xzy.xu@...k-chips.com>
>>>>
>>>> ---
>>>> Hi guys,
>>>>
>>>> I found a similar issue on rk3399 platform, which has a genpd node for
>>>> SD card host. Power off-on pd will reset the registers to a default
>>>> value (ie. CLKENA), so that the host can't output the active clock
>>>> during communication.
>>>>
>>>
>>> Indeed, Caesar recently introduced all the genpd for rk3399 platform,
>>> so we need to restore them.
>>>
>>>> So we need to setup bus in rpm resume. It also wraps the update clock
>>>> behaviour which I did in V3.
>>>>
>>>> Thanks,
>>>> Ziyuan Xu
>>>>
>>>>
>>>> Changes in v4:
>>>> - update commit message
>>>> - fix SD host rpm resume can't work
>>>>
>>>> Changes in v3:
>>>> - only reset host with active slot.
>>>>
>>>> Changes in v2:
>>>> - update the commit message
>>>> - use dw_mci_reset instead of dw_mci_ctrl_reset
>>>>
>>>>  drivers/mmc/host/dw_mmc.c | 6 +++---
>>>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>>>> index b44306b..b6053b3 100644
>>>> --- a/drivers/mmc/host/dw_mmc.c
>>>> +++ b/drivers/mmc/host/dw_mmc.c
>>>> @@ -3354,10 +3354,10 @@ int dw_mci_runtime_resume(struct device *dev)
>>>>
>>>>          if (!slot)
>>>>              continue;
>>>> -        if (slot->mmc->pm_flags & MMC_PM_KEEP_POWER) {
>>>> +        if (slot->mmc->pm_flags & MMC_PM_KEEP_POWER)
>>>>              dw_mci_set_ios(slot->mmc, &slot->mmc->ios);
>>>> -            dw_mci_setup_bus(slot, true);
>>>> -        }
>>>> +        /* Force setup bus to guarantee available clock output */
>>>> +        dw_mci_setup_bus(slot, true);
>>>
>>> So the spamming message about
>>>
>>> "Bus speed (slot %d) = %dHz (slot req %dHz, actual %dHZ div = %d)\n"
>>>
>>> will always be there, right? So you could append a new patch to shut
>>> up it as I think it's useless no matter for system pm or rpm to print
>>> it.  How about?
>>
>> Fine, it's favourable with dev_vdbg if the dw_mmc rpm is enabled.
>> Hi Jaehoon,
>> What's your opinion? If you think this patch and shawn's advice are acceptable, I will send the v5 patch.
>
> I don't agreed to use dev_vdbg()..but it needs not to display at everytime.
> Hmm..It needs to consider more..because we needs to see the clock value when it's initialized.
>

A very stright-forward way is to pass a flag to shut up the spamming
log when it's called from the PM context?

> Best Regards,
> Jaehoon Chung
>
>>
>> BR
>> Ziyuan Xu
>>
>>>
>>>>      }
>>>>
>>>>      /* Now that slots are all setup, we can enable card detect */
>>>>
>>>
>>>
>>
>>
>>
>>
>>
>
>
>
>


-- 
Best Regards
Shawn Lin