Re: [PATCH 2/3] mmc: sdhci-xenon: Try to fix 2G address limitation on AC5 SoC

[Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>]

On 06/08/2022 11:58, Vadym Kochan wrote:
> There is a limitation on AC5 SoC that Xenon SDHC can address only
> first 2GB of memory. Turning to the SDMA mode to use the bounce_buffer
> causes ext_csd recognition to fail on init.
> 
> Using of swiotlb=force also does not help as it is allocated at the
> end of the memory.
> 
> So it was decided to use reserved-memory as a bounce buffer in case
> if the board has more than 2G of memory, or turn on the PIO
> mode if such memory region does not exist in the device-tree.
> 
> It was tested that this approach is 1.5 times faster than PIO.
> 
> Signed-off-by: Vadym Kochan <vadym.kochan@plvision.eu>
> ---
>  drivers/mmc/host/sdhci-xenon.c | 36 ++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-xenon.c b/drivers/mmc/host/sdhci-xenon.c
> index 08e838400b52..fbbd1a045002 100644
> --- a/drivers/mmc/host/sdhci-xenon.c
> +++ b/drivers/mmc/host/sdhci-xenon.c
> @@ -14,8 +14,10 @@
>  #include <linux/acpi.h>
>  #include <linux/delay.h>
>  #include <linux/ktime.h>
> +#include <linux/mm.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/of_reserved_mem.h>
>  #include <linux/pm.h>
>  #include <linux/pm_runtime.h>
>  
> @@ -486,6 +488,31 @@ 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 device *dev = mmc_dev(host->mmc);
> +	struct sysinfo si;
> +	int err;
> +
> +	si_meminfo(&si);
> +
> +	if ((si.totalram * si.mem_unit) > SZ_2G) {
> +		struct device_node *dma_bounce_np;
> +
> +		dma_bounce_np = of_parse_phandle(dev->of_node,
> +						 "marvell,ac5-sdhci-dma-bounce-pool", 0);

No. Undocumented property. Please document all bindings, not only pieces.

> +		err = of_reserved_mem_device_init_by_idx(dev, dma_bounce_np, 0);
> +		of_node_put(dma_bounce_np);
> +		if (err) {
> +			dev_warn(dev, "Disabling DMA because of 2GB DMA access limit and missing DMA bounce region\n");
> +			host->quirks |= SDHCI_QUIRK_BROKEN_ADMA;
> +			host->quirks |= SDHCI_QUIRK_BROKEN_DMA;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  static int xenon_probe(struct platform_device *pdev)
>  {
>  	struct sdhci_pltfm_host *pltfm_host;
> @@ -531,6 +558,12 @@ static int xenon_probe(struct platform_device *pdev)
>  			if (err)
>  				goto err_clk;
>  		}
> +
> +		if (of_device_is_compatible(dev->of_node, "marvell,ac5-sdhci")) {

Don't code compatible comparing in the driver. This is done by matching,
only once. You should use driver data/variant type.

> +			err = xenon_ac5_probe(host);
> +			if (err)
> +				goto err_clk_axi;
> +		}
>  	}
>  
>  	err = mmc_of_parse(host->mmc);
> @@ -570,6 +603,7 @@ static int xenon_probe(struct platform_device *pdev)
>  	pm_runtime_put_noidle(&pdev->dev);
>  	xenon_sdhc_unprepare(host);
>  err_clk_axi:
> +	of_reserved_mem_device_release(&pdev->dev);
>  	clk_disable_unprepare(priv->axi_clk);
>  err_clk:
>  	clk_disable_unprepare(pltfm_host->clk);
> @@ -591,6 +625,7 @@ static int xenon_remove(struct platform_device *pdev)
>  	sdhci_remove_host(host, 0);
>  
>  	xenon_sdhc_unprepare(host);
> +	of_reserved_mem_device_release(&pdev->dev);
>  	clk_disable_unprepare(priv->axi_clk);
>  	clk_disable_unprepare(pltfm_host->clk);
>  
> @@ -682,6 +717,7 @@ 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},

It's not the same.

>  	{}
>  };
>  MODULE_DEVICE_TABLE(of, sdhci_xenon_dt_ids);


Best regards,
Krzysztof