linux-kernel - Re: [PATCH v3 3/3] mmc: xenon: Fix 2G limitation on AC5 SoC

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Date:   Fri, 09 Dec 2022 13:39:25 +0200
From:   Vadym Kochan <vadym.kochan@...ision.eu>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        Hu Ziji <huziji@...vell.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Elad Nachman <enachman@...vell.com>,
        Chris Packham <chris.packham@...iedtelesis.co.nz>
Subject: Re: [PATCH v3 3/3] mmc: xenon: Fix 2G limitation on AC5 SoC

Hi Adrian,

On Fri, 9 Dec 2022 09:23:05 +0200, Adrian Hunter <adrian.hunter@...el.com> wrote:
> On 5/12/22 12:59, Vadym Kochan wrote:
> > There is a limitation on AC5 SoC that mmc controller
> > can't have DMA access over 2G memory, so use SDMA with
> > a bounce buffer. Swiotlb can't help because on arm64 arch
> > it reserves memblock's at the end of the memory.
> > 
> > Additionally set mask to 34 bit since on AC5 SoC RAM starts
> > at 0x2_00000000.
> 
> Can you explain more about how a 34-bit DMA mask works when
> SDMA only supports 32-bit addresses?
> 

So, after I set

> > +		host->flags &= ~SDHCI_USE_64_BIT_DMA;

then sdhc core sets mask to 32 bit, but then dma_map fails to map
bounce buffer because the base address is higher than 32bit - 0x2_00000000,
and 34bit mask fixed it.

> > 
> > Co-developed-by: Elad Nachman <enachman@...vell.com>
> > Signed-off-by: Elad Nachman <enachman@...vell.com>
> > Signed-off-by: Vadym Kochan <vadym.kochan@...ision.eu>
> > ---
> >  drivers/mmc/host/sdhci-xenon.c | 38 ++++++++++++++++++++++++++++++++++
> >  drivers/mmc/host/sdhci-xenon.h |  3 ++-
> >  2 files changed, 40 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mmc/host/sdhci-xenon.c b/drivers/mmc/host/sdhci-xenon.c
> > index 08e838400b52..5f3db0425674 100644
> > --- a/drivers/mmc/host/sdhci-xenon.c
> > +++ b/drivers/mmc/host/sdhci-xenon.c
> > @@ -13,7 +13,9 @@
> >  
> >  #include <linux/acpi.h>
> >  #include <linux/delay.h>
> > +#include <linux/dma-mapping.h>
> >  #include <linux/ktime.h>
> > +#include <linux/mm.h>
> >  #include <linux/module.h>
> >  #include <linux/of.h>
> >  #include <linux/pm.h>
> > @@ -253,6 +255,22 @@ static unsigned int xenon_get_max_clock(struct sdhci_host *host)
> >  		return pltfm_host->clock;
> >  }
> >  
> > +static int xenon_set_dma_mask(struct sdhci_host *host)
> > +{
> > +	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> > +	struct xenon_priv *priv = sdhci_pltfm_priv(pltfm_host);
> > +	struct mmc_host *mmc = host->mmc;
> > +	struct device *dev = mmc_dev(mmc);
> > +
> > +	if (priv->hw_version == XENON_AC5) {
> > +		host->flags &= ~SDHCI_USE_64_BIT_DMA;
> > +
> > +		return dma_set_mask_and_coherent(dev, DMA_BIT_MASK(34));
> > +	}
> > +
> > +	return sdhci_set_dma_mask(host);
> > +}
> > +
> >  static const struct sdhci_ops sdhci_xenon_ops = {
> >  	.voltage_switch		= xenon_voltage_switch,
> >  	.set_clock		= sdhci_set_clock,
> > @@ -261,6 +279,7 @@ static const struct sdhci_ops sdhci_xenon_ops = {
> >  	.reset			= xenon_reset,
> >  	.set_uhs_signaling	= xenon_set_uhs_signaling,
> >  	.get_max_clock		= xenon_get_max_clock,
> > +	.set_dma_mask		= xenon_set_dma_mask,
> >  };
> >  
> >  static const struct sdhci_pltfm_data sdhci_xenon_pdata = {
> > @@ -486,6 +505,18 @@ static void xenon_sdhc_unprepare(struct sdhci_host *host)
> >  	xenon_disable_sdhc(host, sdhc_id);
> >  }
> >  
> > +static int xenon_ac5_probe(struct sdhci_host *host)
> > +{
> > +	struct sysinfo si;
> > +
> > +	si_meminfo(&si);
> > +
> > +	if ((si.totalram * si.mem_unit) > SZ_2G)
> > +		host->quirks |= SDHCI_QUIRK_BROKEN_ADMA;
> > +
> > +	return 0;
> > +}
> > +
> >  static int xenon_probe(struct platform_device *pdev)
> >  {
> >  	struct sdhci_pltfm_host *pltfm_host;
> > @@ -533,6 +564,12 @@ static int xenon_probe(struct platform_device *pdev)
> >  		}
> >  	}
> >  
> > +	if (priv->hw_version == XENON_AC5) {
> > +		err = xenon_ac5_probe(host);
> > +		if (err)
> > +			goto err_clk_axi;
> > +	}
> > +
> >  	err = mmc_of_parse(host->mmc);
> >  	if (err)
> >  		goto err_clk_axi;
> > @@ -682,6 +719,7 @@ static const struct of_device_id sdhci_xenon_dt_ids[] = {
> >  	{ .compatible = "marvell,armada-ap807-sdhci", .data = (void *)XENON_AP807},
> >  	{ .compatible = "marvell,armada-cp110-sdhci", .data =  (void *)XENON_CP110},
> >  	{ .compatible = "marvell,armada-3700-sdhci", .data =  (void *)XENON_A3700},
> > +	{ .compatible = "marvell,ac5-sdhci", .data = (void *)XENON_AC5},
> >  	{}
> >  };
> >  MODULE_DEVICE_TABLE(of, sdhci_xenon_dt_ids);
> > diff --git a/drivers/mmc/host/sdhci-xenon.h b/drivers/mmc/host/sdhci-xenon.h
> > index 3e9c6c908a79..0460d97aad26 100644
> > --- a/drivers/mmc/host/sdhci-xenon.h
> > +++ b/drivers/mmc/host/sdhci-xenon.h
> > @@ -57,7 +57,8 @@ enum xenon_variant {
> >  	XENON_A3700,
> >  	XENON_AP806,
> >  	XENON_AP807,
> > -	XENON_CP110
> > +	XENON_CP110,
> > +	XENON_AC5
> >  };
> >  
> >  struct xenon_priv {
> 

Regards,