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

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Message-ID: <49544a65-9b3c-c56a-e5f7-89c5fa6e6cd0@rock-chips.com>
Date:   Thu, 5 Jan 2017 15:34:16 +0800
From:   Shawn Lin <shawn.lin@...k-chips.com>
To:     Ziyuan Xu <xzy.xu@...k-chips.com>, ulf.hansson@...aro.org,
        jh80.chung@...sung.com, shawn.lin@...k-chips.com
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 2017/1/5 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?

>  	}
>
>  	/* Now that slots are all setup, we can enable card detect */
>


-- 
Best Regards
Shawn Lin