Re: [PATCH] mmc: sdhci-xenon: Fix 2G limitation on AC5 SoC

[Florian Fainelli]

On 7/26/22 10:07, Vadym Kochan wrote:
> From: Elad Nachman <enachman@xxxxxxxxxxx>
> 
> There is a limitation on AC5 SoC that mmc controller
> can't have DMA access over 2G memory.
> 
> Signed-off-by: Elad Nachman <enachman@xxxxxxxxxxx>
> Signed-off-by: Vadym Kochan <vadym.kochan@xxxxxxxxxxx>
> ---
>  drivers/mmc/host/sdhci-xenon.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-xenon.c b/drivers/mmc/host/sdhci-xenon.c
> index 08e838400b52..666d06b58564 100644
> --- a/drivers/mmc/host/sdhci-xenon.c
> +++ b/drivers/mmc/host/sdhci-xenon.c
> @@ -18,6 +18,7 @@
>  #include <linux/of.h>
>  #include <linux/pm.h>
>  #include <linux/pm_runtime.h>
> +#include <linux/mm.h>
>  
>  #include "sdhci-pltfm.h"
>  #include "sdhci-xenon.h"
> @@ -422,6 +423,8 @@ static int xenon_probe_params(struct platform_device *pdev)
>  	struct xenon_priv *priv = sdhci_pltfm_priv(pltfm_host);
>  	u32 sdhc_id, nr_sdhc;
>  	u32 tuning_count;
> +	struct device_node *np = pdev->dev.of_node;
> +	struct sysinfo si;
>  
>  	/* Disable HS200 on Armada AP806 */
>  	if (priv->hw_version == XENON_AP806)
> @@ -450,6 +453,15 @@ static int xenon_probe_params(struct platform_device *pdev)
>  	}
>  	priv->tuning_count = tuning_count;
>  
> +	si_meminfo(&si);
> +
> +	if (of_device_is_compatible(np, "marvell,ac5-sdhci") &&
> +	    ((si.totalram * si.mem_unit) > 0x80000000 /*2G*/)) {

Why not limit the DMA mask of the device and ensure, that bounce buffers get used so you can still do DMA?

Also, you ought to be able to describe that limitation using Device Tree (assuming this is an option) and declaring a dedicated bus node for the SDHCI controller and providing a suitable dma-ranges property, see: arch/arm/boot/dts/bcm2711.dtsi and the 'soc' node for such examples.



> +		host->quirks |= SDHCI_QUIRK_BROKEN_DMA;
> +		host->quirks |= SDHCI_QUIRK_BROKEN_ADMA;
> +		dev_info(mmc_dev(mmc), "Disabling DMA because of 2GB DMA access limit.\n");
> +	}
> +
>  	return xenon_phy_parse_params(dev, host);
>  }
>  
> @@ -682,6 +694,7 @@ 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_AP806},
>  	{}
>  };
>  MODULE_DEVICE_TABLE(of, sdhci_xenon_dt_ids);


-- 
Florian