Re: Query on patch "7ff2760 mmc: core: Add a facility to "pause" re-tuning"

Re: Query on patch "7ff2760 mmc: core: Add a facility to "pause" re-tuning"

[Adrian Hunter]

On 19/05/20 1:42 pm, Y.b. Lu wrote:
> Hi Uffe and Adrian,
> 
>  
> 
> May I have a query on below patch. Do we really need re-tuning before
> switching to RPMB partition each time per eMMC spec, especially for HS400
> mode with auto-tuning?

It was to ensure tuning would not be needed while accessing RPMB since RPMB
does not support tuning.

> 
> What’s the impact if no re-tuning here?

Increased risk of CRC errors.

> 
>  
> 
> 7ff2760 mmc: core: Add a facility to "pause" re-tuning
> 
>  
> 
> +/*
> 
> + * Pause re-tuning for a small set of operations.  The pause begins after the
> 
> + * next command and after first doing re-tuning.
> 
> + */
> 
> +void mmc_retune_pause(struct mmc_host *host)
> 
> +{
> 
> +       if (!host->retune_paused) {
> 
> +               host->retune_paused = 1;
> 
> +               mmc_retune_needed(host);
> 
> +               mmc_retune_hold(host);
> 
> +       }
> 
> +}
> 
>  
> 
> Thanks a lot.
> 
>  
> 
> Best regards,
> 
> Yangbo Lu
> 
>  
> 

RE: Query on patch "7ff2760 mmc: core: Add a facility to "pause" re-tuning"

[Y.b. Lu]

Hi Adrian,

Thanks for your quick explaining.
Auto tuning mode make sure tuning would not be needed as hardware will automatically take care of drift for data transfer.
And the chances of drift on response line (48 cycles) is very less.

Ok. The retuning can reduce the risk of CRC errors even the risk is very low for auto tuning mode.
I have no question now:)

Thanks a lot.

Best regards,
Yangbo Lu

> -----Original Message-----
> From: linux-mmc-owner@vger.kernel.org <linux-mmc-owner@vger.kernel.org>
> On Behalf Of Adrian Hunter
> Sent: Tuesday, May 19, 2020 6:57 PM
> To: Y.b. Lu <yangbo.lu@nxp.com>; Ulf Hansson <ulf.hansson@linaro.org>;
> linux-mmc@vger.kernel.org
> Cc: Sachin Miglani <sachin.miglani@nxp.com>
> Subject: Re: Query on patch "7ff2760 mmc: core: Add a facility to "pause"
> re-tuning"
> 
> On 19/05/20 1:42 pm, Y.b. Lu wrote:
> > Hi Uffe and Adrian,
> >
> >
> >
> > May I have a query on below patch. Do we really need re-tuning before
> > switching to RPMB partition each time per eMMC spec, especially for HS400
> > mode with auto-tuning?
> 
> It was to ensure tuning would not be needed while accessing RPMB since
> RPMB
> does not support tuning.
> 
> >
> > What's the impact if no re-tuning here?
> 
> Increased risk of CRC errors.
> 
> >
> >
> >
> > 7ff2760 mmc: core: Add a facility to "pause" re-tuning
> >
> >
> >
> > +/*
> >
> > + * Pause re-tuning for a small set of operations.  The pause begins after the
> >
> > + * next command and after first doing re-tuning.
> >
> > + */
> >
> > +void mmc_retune_pause(struct mmc_host *host)
> >
> > +{
> >
> > +       if (!host->retune_paused) {
> >
> > +               host->retune_paused = 1;
> >
> > +               mmc_retune_needed(host);
> >
> > +               mmc_retune_hold(host);
> >
> > +       }
> >
> > +}
> >
> >
> >
> > Thanks a lot.
> >
> >
> >
> > Best regards,
> >
> > Yangbo Lu
> >
> >
> >