linux-kernel - Re: [PATCH 2/3] mmc: sdhci-iproc: Cap min clock frequency on BCM2711

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Date:   Wed, 07 Apr 2021 10:44:39 +0200
From:   Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
To:     Stefan Wahren <stefan.wahren@...e.com>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-mmc@...r.kernel.org,
        devicetree@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org,
        Ray Jui <ray.jui@...adcom.com>,
        Scott Branden <scott.branden@...adcom.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Stefan Wahren <wahrenst@....net>,
        Matthias Brugger <mbrugger@...e.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ray Jui <rjui@...adcom.com>,
        Scott Branden <sbranden@...adcom.com>
Cc:     f.fainelli@...il.com, phil@...pberrypi.com,
        tim.gover@...pberrypi.com, alcooperx@...il.com,
        linux-kernel@...r.kernel.org, robh@...nel.org
Subject: Re: [PATCH 2/3] mmc: sdhci-iproc: Cap min clock frequency on BCM2711

On Tue, 2021-04-06 at 19:59 +0200, Stefan Wahren wrote:
> Hi Nicolas,
> 
> Am 06.04.21 um 12:48 schrieb Nicolas Saenz Julienne:
> > There is a known bug on BCM2711's SDHCI core integration where the
> > controller will hang when the difference between the core clock and the
> > bus clock is too great. Specifically this can be reproduced under the
> > following conditions:
> > 
> > - No SD card plugged in, polling thread is running, probing cards at
> >   100KHz.
> > - BCM2711's core clock configured at 500MHz or more.
> > 
> > So set 200MHz as the minimum clock frequency available for that board.
> i think it should be 200 kHz?

Of course... Sorry for that.

Regards,
Nicolas

> > 
> > For more information on the issue see this:
> > https://lore.kernel.org/linux-mmc/20210322185816.27582-1-nsaenz@kernel.org/T/#m11f2783a09b581da6b8a15f302625b43a6ecdeca
> > 
> > Fixes: f84e411c85be ("mmc: sdhci-iproc: Add support for emmc2 of the BCM2711")
> > Signed-off-by: Nicolas Saenz Julienne <nsaenz@...nel.org>
> > ---
> >  drivers/mmc/host/sdhci-iproc.c | 18 ++++++++++++++++++
> >  1 file changed, 18 insertions(+)
> > 
> > diff --git a/drivers/mmc/host/sdhci-iproc.c b/drivers/mmc/host/sdhci-iproc.c
> > index ddeaf8e1f72f..1ef888e91f73 100644
> > --- a/drivers/mmc/host/sdhci-iproc.c
> > +++ b/drivers/mmc/host/sdhci-iproc.c
> > @@ -173,6 +173,23 @@ static unsigned int sdhci_iproc_get_max_clock(struct sdhci_host *host)
> >  		return pltfm_host->clock;
> >  }
> >  
> > 
> > +/*
> > + * There is a known bug on BCM2711's SDHCI core integration where the
> > + * controller will hang when the difference between the core clock and the bus
> > + * clock is too great. Specifically this can be reproduced under the following
> > + * conditions:
> > + *
> > + *  - No SD card plugged in, polling thread is running, probing cards at
> > + *    100KHz.
> > + *  - BCM2711's core clock configured at 500MHz or more
> > + *
> > + * So we set 200MHz as the minimum clock frequency available for that SoC.
> > + */
> > +static unsigned int sdhci_iproc_bcm2711_get_min_clock(struct sdhci_host *host)
> > +{
> > +	return 200000;
> > +}
> > +
> >  static const struct sdhci_ops sdhci_iproc_ops = {
> >  	.set_clock = sdhci_set_clock,
> >  	.get_max_clock = sdhci_iproc_get_max_clock,
> > @@ -271,6 +288,7 @@ static const struct sdhci_ops sdhci_iproc_bcm2711_ops = {
> >  	.set_clock = sdhci_set_clock,
> >  	.set_power = sdhci_set_power_and_bus_voltage,
> >  	.get_max_clock = sdhci_iproc_get_max_clock,
> > +	.get_min_clock = sdhci_iproc_bcm2711_get_min_clock,
> >  	.set_bus_width = sdhci_set_bus_width,
> >  	.reset = sdhci_reset,
> >  	.set_uhs_signaling = sdhci_set_uhs_signaling,



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