linux-kernel - Re: [PATCH v2 2/2] mmc: sdhci-pci: Use ACPI to get max frequency for Intel byt sdio controller sub-vended by NI

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Date:   Wed, 23 Nov 2016 09:35:10 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Zach Brown <zach.brown@...com>, ulf.hansson@...aro.org
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] mmc: sdhci-pci: Use ACPI to get max frequency for
 Intel byt sdio controller sub-vended by NI

On 22/11/16 23:53, Zach Brown wrote:
> On NI 9037 boards the max SDIO frequency is limited by trace lengths
> and other layout choices. The max SDIO frequency is stored in an ACPI
> table.
> 
> The driver reads the ACPI entry MXFQ during sdio_probe_slot and sets the
> f_max field of the host.
> 
> Signed-off-by: Nathan Sullivan <nathan.sullivan@...com>
> Reviewed-by: Jaeden Amero <jaeden.amero@...com>
> Reviewed-by: Josh Cartwright <joshc@...com>
> Signed-off-by: Zach Brown <zach.brown@...com>
> ---
>  drivers/mmc/host/sdhci-pci-core.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-pci-core.c b/drivers/mmc/host/sdhci-pci-core.c
> index 9741505..34284b8 100644
> --- a/drivers/mmc/host/sdhci-pci-core.c
> +++ b/drivers/mmc/host/sdhci-pci-core.c
> @@ -27,6 +27,7 @@
>  #include <linux/pm_runtime.h>
>  #include <linux/mmc/slot-gpio.h>
>  #include <linux/mmc/sdhci-pci-data.h>
> +#include <linux/acpi.h>
>  
>  #include "sdhci.h"
>  #include "sdhci-pci.h"
> @@ -375,6 +376,30 @@ static int byt_emmc_probe_slot(struct sdhci_pci_slot *slot)
>  	return 0;
>  }
>  
> +#ifdef CONFIG_ACPI
> +
> +static int ni_byt_sdio_probe_slot(struct sdhci_pci_slot *slot)
> +{
> +	acpi_status status;
> +	unsigned long long max_freq;
> +
> +	status = acpi_evaluate_integer(ACPI_HANDLE(&slot->chip->pdev->dev),
> +				       "MXFQ", NULL, &max_freq);
> +	if (ACPI_FAILURE(status)) {
> +		dev_err(&slot->chip->pdev->dev,
> +			"MXFQ not found in acpi table\n");
> +		return -EINVAL;
> +	}
> +
> +	slot->host->mmc->f_max = max_freq * 1000000;
> +
> +	slot->host->mmc->caps |= MMC_CAP_POWER_OFF_CARD | MMC_CAP_NONREMOVABLE |
> +				 MMC_CAP_WAIT_WHILE_BUSY;
> +	return 0;
> +}
> +
> +#else

No, it is the ACPI access that needs to be a separate function.  We don't
want 2 ni_byt_sdio_probe_slot(). Perhaps, something like:

#ifdef CONFIG_ACPI
static int ni_set_max_freq(struct sdhci_pci_slot *slot)
{
	acpi_status status;
	unsigned long long max_freq;

	status = acpi_evaluate_integer(ACPI_HANDLE(&slot->chip->pdev->dev),
				       "MXFQ", NULL, &max_freq);
	if (ACPI_FAILURE(status))
		dev_err(&slot->chip->pdev->dev,
			"MXFQ not found in acpi table\n");
		return -EINVAL;
	}

	slot->host->mmc->f_max = max_freq * 1000000;

	return 0;
}
#else
static inline int ni_set_max_freq(struct sdhci_pci_slot *slot)
{
	return 0;
}
#endif