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    SubjectRe: [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@intel.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@marvell.com>
    > > Signed-off-by: Elad Nachman <enachman@marvell.com>
    > > Signed-off-by: Vadym Kochan <vadym.kochan@plvision.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,

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