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

[Adrian Hunter]

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)

> 
>>>
>>>>>
>>>>> 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,
>>