On 29 March 2018 at 19:44, Jennifer Dahm <jennifer.dahm@xxxxxx> wrote:
> From: Kyle Roeschley <kyle.roeschley@xxxxxx>
>
> On some SD host controllers, 1.8V signaling is required for reliable
> operation of the part. Add a capability which says that we must switch
> to 1.8V signaling during card initialization.
This makes no sense to me, sorry. SD cards, according to the spec,
must always be initialized at 3.3 V I/O, before they can be switched
to UHS mode and 1.8 V I/O.
So if your host have issues with supporting 3.3 V I/O for an SD card
slot, you are in trouble anyways. Or what am I missing?
Kind regards
Uffe
>
> Signed-off-by: Kyle Roeschley <kyle.roeschley@xxxxxx>
> Signed-off-by: Jennifer Dahm <jennifer.dahm@xxxxxx>
> ---
> drivers/mmc/core/sd.c | 7 +++++++
> include/linux/mmc/host.h | 1 +
> 2 files changed, 8 insertions(+)
>
> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> index baf3d5d..b259671 100644
> --- a/drivers/mmc/core/sd.c
> +++ b/drivers/mmc/core/sd.c
> @@ -782,6 +782,13 @@ int mmc_sd_get_cid(struct mmc_host *host, u32 ocr, u32 *cid, u32 *rocr)
> }
> }
>
> + if (host->caps2 & MMC_CAP2_REQUIRE_1_8V &&
> + host->ios.signal_voltage != MMC_SIGNAL_VOLTAGE_180) {
> + pr_err("%s: Host requires UHS-capable card\n",
> + mmc_hostname(host));
> + return -EINVAL;
> + }
> +
> err = mmc_send_cid(host, cid);
> return err;
> }
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 8514623..4d58c10 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -354,6 +354,7 @@ struct mmc_host {
> #define MMC_CAP2_NO_MMC (1 << 22) /* Do not send (e)MMC commands during initialization */
> #define MMC_CAP2_CQE (1 << 23) /* Has eMMC command queue engine */
> #define MMC_CAP2_CQE_DCMD (1 << 24) /* CQE can issue a direct command */
> +#define MMC_CAP2_REQUIRE_1_8V (1 << 25) /* Host requires 1.8V signalling */
>
> int fixed_drv_type; /* fixed driver type for non-removable media */
>
> --
> 2.7.4
>
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