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

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Message-ID: <ce870974-3e4f-107f-2047-89dcaebff1a2@intel.com>
Date:   Fri, 9 Dec 2022 13:53:58 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Vadym Kochan <vadym.kochan@...ision.eu>,
        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

On 9/12/22 13:39, Vadym Kochan wrote:
> 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.

What happens if the bounce buffer gets mapped in the range
0x1_00000000 to 0x1_ffffffff ?

> 
>>>
>>> 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,