linux-kernel - Re: [PATCH v3 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:   Thu, 1 Dec 2016 09:52:22 +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 v3 2/2] mmc: sdhci-pci: Use ACPI to get max frequency for
 Intel byt sdio controller sub-vended by NI

On 28/11/16 21:16, 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>

Acked-by: Adrian Hunter <adrian.hunter@...el.com>

> ---
>  drivers/mmc/host/sdhci-pci-core.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-pci-core.c b/drivers/mmc/host/sdhci-pci-core.c
> index 9741505..c9e51b1 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"
> @@ -375,8 +376,39 @@ static int byt_emmc_probe_slot(struct sdhci_pci_slot *slot)
>  	return 0;
>  }
>  
> +#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
> +
>  static int ni_byt_sdio_probe_slot(struct sdhci_pci_slot *slot)
>  {
> +	int err;
> +
> +	err = ni_set_max_freq(slot);
> +	if (err)
> +		return err;
> +
>  	slot->host->mmc->caps |= MMC_CAP_POWER_OFF_CARD | MMC_CAP_NONREMOVABLE |
>  				 MMC_CAP_WAIT_WHILE_BUSY;
>  	return 0;
>