linux-kernel - Re: [PATCH 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:   Tue, 22 Nov 2016 09:24:33 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Zach Brown <zach.brown@...com>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] mmc: sdhci-pci: Use ACPI to get max frequency for
 Intel byt sdio controller sub-vended by NI

On 22 November 2016 at 00:04, Zach Brown <zach.brown@...com> 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 | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-pci-core.c b/drivers/mmc/host/sdhci-pci-core.c
> index 9741505..a855c97 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"
> @@ -377,6 +378,20 @@ static int byt_emmc_probe_slot(struct sdhci_pci_slot *slot)
>
>  static int ni_byt_sdio_probe_slot(struct sdhci_pci_slot *slot)
>  {
> +#ifdef CONFIG_ACPI

I am not a fan of these kind of "ifdefs" immediately in the code. I
rather see them around functions.

Either separate the code within the ifdefs here into it's own function
(and call it from here) and make a stub function in case when
CONFIG_ACPI is unset. Or, perhaps easier, have one version of
ni_byt_sdio_probe_slot() when CONFIG_ACPI is set and another one when
it's unset.


> +       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_info(&slot->chip->pdev->dev,
> +                       "MXFQ not found in acpi table\n");
> +               return -EINVAL;
> +       }
> +
> +       slot->host->mmc->f_max = max_freq * 1000000;
> +#endif
>         slot->host->mmc->caps |= MMC_CAP_POWER_OFF_CARD | MMC_CAP_NONREMOVABLE |
>                                  MMC_CAP_WAIT_WHILE_BUSY;
>         return 0;
> --
> 2.7.4
>

Kind regards
Uffe