Re: [PATCH v3 3/3] mmc: xenon: Fix 2G limitation on AC5 SoC
From: Vadym Kochan
Date: Mon Dec 12 2022 - 06:40:43 EST
Hi Adrian,
On Mon, 12 Dec 2022 10:42:36 +0200, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
> On 9/12/22 15:27, Vadym Kochan wrote:
> > On Fri, 9 Dec 2022 14:13:06 +0200, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
> >> On 9/12/22 14:10, Vadym Kochan wrote:
> >>> Hi Adrian,
> >>>
> >>> On Fri, 9 Dec 2022 13:53:58 +0200, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote:
> >>>> On 9/12/22 13:39, Vadym Kochan wrote:
> >>>>> Hi Adrian,
> >>>>>
> >>>>> On Fri, 9 Dec 2022 09:23:05 +0200, Adrian Hunter <adrian.hunter@xxxxxxxxx> 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.
> >>>>
> >>>> What happens if the bounce buffer gets mapped in the range
> >>>> 0x1_00000000 to 0x1_ffffffff ?
> >>>>
> >>>
> >>> From my understanding, on the AC5 SoC RAM starts at 0x2_00000000 so the bounce
> >>> buffer can be mapped in the range 0x2_00000000..0x2_ffffffff
> >>
> >> Right but I guess I meant what about 0x3_00000000..0x3_ffffffff ?
> >> Isn't that also in DMA_BIT_MASK(34)
> >
> > Yes, you are right.
>
> So it would fail in that case? Is it possible to use devicetree
> reserved memory or some such, to set aside 64k for the bounce
> buffer DMA mapping?
>
The main restriction is that only lower 2GB can be used for DMA.
I already did send solution based on reserved memory, I can send it again in context of this series.
Also what about the solution which Linus suggested ?
[cut]
Let's just create a new quirk:
SDHCI_QUIRK_31BIT_DMA_ROOF
Define the semantics such that this will allow DMA for buffers that are below
the 31st bit, but does not have the semantics to limit scatter-gather buffers to
be 32-bit aligned.
[/cut]
Thanks,
> >
> >>
> >>>
> >>>>>
> >>>>>>>
> >>>>>>> Co-developed-by: Elad Nachman <enachman@xxxxxxxxxxx>
> >>>>>>> Signed-off-by: Elad Nachman <enachman@xxxxxxxxxxx>
> >>>>>>> Signed-off-by: Vadym Kochan <vadym.kochan@xxxxxxxxxxx>
> >>>>>>> ---
> >>>>>>> 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,
> >>>>
> >>
>