mmc: core: Prepare to support SD UHS-II cards

The SD UHS-II interface was introduced to the SD spec v4.00 several years
ago. The interface is fundamentally different from an electrical and a
protocol point of view, comparing to the legacy SD interface.

However, the legacy SD protocol is supported through a specific transport
layer (SD-TRAN) defined in the UHS-II addendum of the spec. This allows the
SD card to be managed in a very similar way as a legacy SD card, hence a
lot of code can be re-used to support these new types of cards through the
mmc subsystem.

Moreover, an SD card that supports the UHS-II interface shall also be
backwards compatible with the legacy SD interface, which allows a UHS-II
card to be inserted into a legacy slot. As a matter of fact, this is
already supported by mmc subsystem as of today.

To prepare to add support for UHS-II, this change puts the basic foundation
in the mmc core in place, allowing it to be more easily reviewed before
subsequent changes implements the actual support.

Basically, the approach here adds a new UHS-II bus_ops type and adds a
separate initialization path for the UHS-II card. The intent is to avoid us
from sprinkling the legacy initialization path, but also to simplify
implementation of the UHS-II specific bits.

At this point, there is only one new host ops added to manage the various
ios settings needed for UHS-II. Additional host ops that are needed, are
being added from subsequent changes.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20240913102836.6144-3-victorshihgli@gmail.com

2 files changed, 30 insertions, 0 deletions

diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index eb67d3d5ff5b..0bb1ad1ea4dc 100644
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -209,6 +209,11 @@ struct sd_ext_reg {
 #define SD_EXT_PERF_CMD_QUEUE	(1<<4)
 };
 
+struct sd_uhs2_config {
+	u32			node_id;
+	/* TODO: Extend with more register configs. */
+};
+
 struct sdio_cccr {
 	unsigned int		sdio_vsn;
 	unsigned int		sd_vsn;
@@ -320,6 +325,8 @@ struct mmc_card {
 	struct sd_ext_reg	ext_power;	/* SD extension reg for PM */
 	struct sd_ext_reg	ext_perf;	/* SD extension reg for PERF */
 
+	struct sd_uhs2_config	uhs2_config;	/* SD UHS-II config */
+
 	unsigned int		sdio_funcs;	/* number of SDIO functions */
 	atomic_t		sdio_funcs_probed; /* number of probed SDIO funcs */
 	struct sdio_cccr	cccr;		/* common card info */
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 8fc2b328ec4d..e1d380de3aaa 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -64,6 +64,10 @@ struct mmc_ios {
 #define MMC_TIMING_MMC_HS400	10
 #define MMC_TIMING_SD_EXP	11
 #define MMC_TIMING_SD_EXP_1_2V	12
+#define MMC_TIMING_UHS2_SPEED_A    13
+#define MMC_TIMING_UHS2_SPEED_A_HD 14
+#define MMC_TIMING_UHS2_SPEED_B    15
+#define MMC_TIMING_UHS2_SPEED_B_HD 16
 
 	unsigned char	signal_voltage;		/* signalling voltage (1.8V or 3.3V) */
 
@@ -92,6 +96,14 @@ struct mmc_clk_phase_map {
 	struct mmc_clk_phase phase[MMC_NUM_CLK_PHASES];
 };
 
+struct sd_uhs2_caps {
+	/* TODO: Add UHS-II capabilities for the host. */
+};
+
+enum sd_uhs2_operation {
+	UHS2_SET_IOS,
+};
+
 struct mmc_host;
 
 enum mmc_err_stat {
@@ -219,6 +231,14 @@ struct mmc_host_ops {
 
 	/* Initialize an SD express card, mandatory for MMC_CAP2_SD_EXP. */
 	int	(*init_sd_express)(struct mmc_host *host, struct mmc_ios *ios);
+
+	/*
+	 * The uhs2_control callback is used to execute SD UHS-II specific
+	 * operations. It's mandatory to implement for hosts that supports the
+	 * SD UHS-II interface (MMC_CAP2_SD_UHS2). Expected return values are a
+	 * negative errno in case of a failure or zero for success.
+	 */
+	int	(*uhs2_control)(struct mmc_host *host, enum sd_uhs2_operation op);
 };
 
 struct mmc_cqe_ops {
@@ -379,6 +399,7 @@ struct mmc_host {
 				 MMC_CAP2_HS200_1_2V_SDR)
 #define MMC_CAP2_SD_EXP		(1 << 7)	/* SD express via PCIe */
 #define MMC_CAP2_SD_EXP_1_2V	(1 << 8)	/* SD express 1.2V */
+#define MMC_CAP2_SD_UHS2	(1 << 9)	/* SD UHS-II support */
 #define MMC_CAP2_CD_ACTIVE_HIGH	(1 << 10)	/* Card-detect signal active high */
 #define MMC_CAP2_RO_ACTIVE_HIGH	(1 << 11)	/* Write-protect signal active high */
 #define MMC_CAP2_NO_PRESCAN_POWERUP (1 << 14)	/* Don't power up before scan */
@@ -405,6 +426,8 @@ struct mmc_host {
 #endif
 #define MMC_CAP2_ALT_GPT_TEGRA	(1 << 28)	/* Host with eMMC that has GPT entry at a non-standard location */
 
+	struct sd_uhs2_caps	uhs2_caps;	/* Host UHS-II capabilities */
+
 	int			fixed_drv_type;	/* fixed driver type for non-removable media */
 
 	mmc_pm_flag_t		pm_caps;	/* supported pm features */