linux-kernel - Re: [PATCH] mmc: rtsx: add 74 Clocks in power on flow

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Message-ID: <YhSl4WuE2Dpil/Zj@kroah.com>
Date:   Tue, 22 Feb 2022 09:59:13 +0100
From:   "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
To:     Ricky WU <ricky_wu@...ltek.com>
Cc:     "ulf.hansson@...aro.org" <ulf.hansson@...aro.org>,
        "kai.heng.feng@...onical.com" <kai.heng.feng@...onical.com>,
        "tommyhebb@...il.com" <tommyhebb@...il.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: rtsx: add 74 Clocks in power on flow

On Tue, Feb 22, 2022 at 08:48:30AM +0000, Ricky WU wrote:
> > -----Original Message-----
> > From: gregkh@...uxfoundation.org <gregkh@...uxfoundation.org>
> > Sent: Tuesday, February 22, 2022 3:42 PM
> > To: Ricky WU <ricky_wu@...ltek.com>
> > Cc: ulf.hansson@...aro.org; kai.heng.feng@...onical.com;
> > tommyhebb@...il.com; linux-mmc@...r.kernel.org;
> > linux-kernel@...r.kernel.org
> > Subject: Re: [PATCH] mmc: rtsx: add 74 Clocks in power on flow
> > 
> > On Tue, Feb 22, 2022 at 07:27:52AM +0000, Ricky WU wrote:
> > > After 1ms stabilizing the voltage time add "Host provides at least 74
> > > Clocks before issuing first command" that is spec definition
> > 
> > You do have 72 columns to use here, no need to wrap this so tightly.
> >
> 
> Ok...
> so I need to have next patch to fix this format?

Please do, because:

> 
> > >
> > > Signed-off-by: Ricky Wu <ricky_wu@...ltek.com>
> > > ---
> > >  drivers/mmc/host/rtsx_pci_sdmmc.c | 7 +++++++
> > >  1 file changed, 7 insertions(+)
> > >
> > > diff --git a/drivers/mmc/host/rtsx_pci_sdmmc.c
> > > b/drivers/mmc/host/rtsx_pci_sdmmc.c
> > > index 2a3f14afe9f8..e016d720e453 100644
> > > --- a/drivers/mmc/host/rtsx_pci_sdmmc.c
> > > +++ b/drivers/mmc/host/rtsx_pci_sdmmc.c
> > > @@ -940,10 +940,17 @@ static int sd_power_on(struct realtek_pci_sdmmc
> > *host)
> > >  	if (err < 0)
> > >  		return err;
> > >
> > > +	mdelay(1);
> > 
> > What is this delay for?
> >
> 
> Spec definition, need to wait 1ms for voltage stable
> and below mdelay(5) is our device send 74 Clocks time

Clock cycles and mdelay() are not going to always stay the same, right?

I really have no idea what "74 clocks time" means, is this some specific
timing value for this hardware?  What is the units?  This needs to be
documented better in both the changelog and in the code.

thanks,

greg k-h