RE: [PATCH] mmc: host: sdhci-esdhc-imx: reset usdhc before sending tuning command for manual tuning method

From: Bough Chen <haibo.chen@nxp.com>
To: Adrian Hunter <adrian.hunter@intel.com>,
	"ulf.hansson@linaro.org" <ulf.hansson@linaro.org>,
	"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>
Cc: dl-linux-imx <linux-imx@nxp.com>,
	"shawnguo@kernel.org" <shawnguo@kernel.org>,
	"s.hauer@pengutronix.de" <s.hauer@pengutronix.de>,
	"kernel@pengutronix.de" <kernel@pengutronix.de>,
	"festevam@gmail.com" <festevam@gmail.com>
Subject: RE: [PATCH] mmc: host: sdhci-esdhc-imx: reset usdhc before sending tuning command for manual tuning method
Date: Fri, 7 Aug 2020 01:50:03 +0000	[thread overview]
Message-ID: <VI1PR04MB52945822087D81437FA6CCC590490@VI1PR04MB5294.eurprd04.prod.outlook.com> (raw)
In-Reply-To: <d3e56b01-144b-17cf-d414-9e0d558b9bcc@intel.com>

> -----Original Message-----
> From: Adrian Hunter [mailto:adrian.hunter@intel.com]
> Sent: 2020年8月6日 20:11
> To: Bough Chen <haibo.chen@nxp.com>; ulf.hansson@linaro.org;
> linux-mmc@vger.kernel.org
> Cc: dl-linux-imx <linux-imx@nxp.com>; shawnguo@kernel.org;
> s.hauer@pengutronix.de; kernel@pengutronix.de; festevam@gmail.com
> Subject: Re: [PATCH] mmc: host: sdhci-esdhc-imx: reset usdhc before sending
> tuning command for manual tuning method
> 
> On 6/08/20 2:48 pm, haibo.chen@nxp.com wrote:
> > From: Haibo Chen <haibo.chen@nxp.com>
> >
> > According to IC suggestion, everytime before sending the tuning
> > command, need to reset the usdhc, so to reset the tuning circuit, to
> > let every tuning command work well for the manual tuning method. For
> > standard tuning method, IC already add the reset operation in the logic.
> >
> > Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
> > ---
> >  drivers/mmc/host/sdhci-esdhc-imx.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c
> > b/drivers/mmc/host/sdhci-esdhc-imx.c
> > index a76b4513fbec..e4694eb1b914 100644
> > --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> > +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> > @@ -990,6 +990,7 @@ static void esdhc_prepare_tuning(struct sdhci_host
> > *host, u32 val)
> >
> >  	/* FIXME: delay a bit for card to be ready for next tuning due to errors */
> >  	mdelay(1);
> > +	sdhci_reset(host, SDHCI_RESET_ALL);
> 
> Doesn't that reset all registers i.e. the entire ios state?
> 

Hi Adrian,
For i.MX usdhc, RESET_ALL operation do not impact any register value, it just reset the internal logic setting. I already verified that.
Here I just want to set the SDHCI_RESET_ALL bit, but I notice that the API sdhci_reset() will also touch the host->clock, so I'm not sure whether it is good enough to use this API directly. Any suggestion? At least, current patch can fix the manual tuning issue on imx7d/imx8qxp.

> >
> >  	reg = readl(host->ioaddr + ESDHC_MIX_CTRL);
> >  	reg |= ESDHC_MIX_CTRL_EXE_TUNE | ESDHC_MIX_CTRL_SMPCLK_SEL |
> >