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SubjectRe: [PATCH 2/3] mmc: sdhci: sdhci-pci-o2micro: Check if controller supports 8-bit width
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On 10/06/19 9:53 PM, Raul E Rangel wrote:
> The O2 controller supports 8-bit EMMC access. mmc_select_bus_width()
> will be used to determine if the MMC supports 8-bit or 4-bit access.

The problem is that the bit indicates a host controller capability, not how
many data lines there actually are on the board. Will this break something
that does not have 8 lines?

>
> Signed-off-by: Raul E Rangel <rrangel@chromium.org>
> ---
> 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 | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-pci-o2micro.c b/drivers/mmc/host/sdhci-pci-o2micro.c
> index dd21315922c87..07bb91cbdf1f8 100644
> --- a/drivers/mmc/host/sdhci-pci-o2micro.c
> +++ b/drivers/mmc/host/sdhci-pci-o2micro.c
> @@ -395,11 +395,16 @@ 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);
> + 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:
>

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