linux-kernel - Re: [PATCH v2 2/3] mmc: sdhci: sdhci-pci-o2micro: Check if controller supports 8-bit width

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Date:   Tue, 18 Jun 2019 13:40:53 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Raul E Rangel <rrangel@...omium.org>
Cc:     "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "ernest.zhang" <ernest.zhang@...hubtech.com>,
        Daniel Kurtz <djkurtz@...omium.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Adrian Hunter <adrian.hunter@...el.com>
Subject: Re: [PATCH v2 2/3] mmc: sdhci: sdhci-pci-o2micro: Check if controller
 supports 8-bit width

On Mon, 17 Jun 2019 at 22:10, Raul E Rangel <rrangel@...omium.org> wrote:
>
> The O2 controller supports 8-bit EMMC access.
>
> JESD84-B51 section A.6.3.a defines the bus testing procedure that
> `mmc_select_bus_width()` implements. This is used to determine the actual
> bus width of the eMMC.
>
> Signed-off-by: Raul E Rangel <rrangel@...omium.org>

Applied for next, thanks!

Kind regards
Uffe



> ---
> I tested this on an AMD chromebook.
>
> $ cat /sys/kernel/debug/mmc1/ios
> clock:          200000000 Hz
> actual clock:   200000000 Hz
> vdd:            21 (3.3 ~ 3.4 V)
> bus mode:       2 (push-pull)
> chip select:    0 (don't care)
> power mode:     2 (on)
> bus width:      3 (8 bits)
> timing spec:    9 (mmc HS200)
> signal voltage: 1 (1.80 V)
> driver type:    0 (driver type B)
>
> Before this patch only 4 bit was negotiated.
>
>  drivers/mmc/host/sdhci-pci-o2micro.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-pci-o2micro.c b/drivers/mmc/host/sdhci-pci-o2micro.c
> index dd21315922c87..9dc4548271b4b 100644
> --- a/drivers/mmc/host/sdhci-pci-o2micro.c
> +++ b/drivers/mmc/host/sdhci-pci-o2micro.c
> @@ -395,11 +395,21 @@ int sdhci_pci_o2_probe_slot(struct sdhci_pci_slot *slot)
>  {
>         struct sdhci_pci_chip *chip;
>         struct sdhci_host *host;
> -       u32 reg;
> +       u32 reg, caps;
>         int ret;
>
>         chip = slot->chip;
>         host = slot->host;
> +
> +       caps = sdhci_readl(host, SDHCI_CAPABILITIES);
> +
> +       /*
> +        * mmc_select_bus_width() will test the bus to determine the actual bus
> +        * width.
> +        */
> +       if (caps & SDHCI_CAN_DO_8BIT)
> +               host->mmc->caps |= MMC_CAP_8_BIT_DATA;
> +
>         switch (chip->pdev->device) {
>         case PCI_DEVICE_ID_O2_SDS0:
>         case PCI_DEVICE_ID_O2_SEABIRD0:
> --
> 2.22.0.410.gd8fdbe21b5-goog
>