Drivers for MMC hosts that accept phase corrections can take advantage
of the helper by embedding a mmc_clk_phase_map_t object in their
private data and invoking mmc_of_parse_clk_phase() to extract phase
parameters. It is the responsibility of the host driver to translate and
apply the extracted values to hardware as required.

Signed-off-by: Andrew Jeffery <redacted>
---
 drivers/mmc/core/host.c  | 44 ++++++++++++++++++++++++++++++++++++++++
 include/linux/mmc/host.h | 17 ++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
index 96b2ca1f1b06..b1697f00c4b5 100644
--- a/drivers/mmc/core/host.c
+++ b/drivers/mmc/core/host.c

@@ -163,6 +163,50 @@ static void mmc_retune_timer(struct timer_list *t)
        mmc_retune_needed(host);
 }

+static void mmc_of_parse_timing_phase(struct device *dev, const char *prop,
+                                     struct mmc_clk_phase *phase)
+{
+       int degrees[2] = {0};
+       int rc;
+
+       rc = device_property_read_u32_array(dev, prop, degrees, 2);
+       phase->valid = !rc;
+       if (phase->valid) {
+               phase->in_deg = degrees[0];
+               phase->out_deg = degrees[1];
+       }
+}
+
+void
+mmc_of_parse_clk_phase(struct mmc_host *host, mmc_clk_phase_map_t map)

+{
+       struct device *dev = host->parent;
+
+       mmc_of_parse_timing_phase(dev, "clk-phase-legacy",
+                                 &map[MMC_TIMING_LEGACY]);
+       mmc_of_parse_timing_phase(dev, "clk-phase-mmc-hs",
+                                 &map[MMC_TIMING_MMC_HS]);
+       mmc_of_parse_timing_phase(dev, "clk-phase-sd-hs",
+                                 &map[MMC_TIMING_SD_HS]);
+       mmc_of_parse_timing_phase(dev, "clk-phase-uhs-sdr12",
+                                 &map[MMC_TIMING_UHS_SDR12]);
+       mmc_of_parse_timing_phase(dev, "clk-phase-uhs-sdr25",
+                                 &map[MMC_TIMING_UHS_SDR25]);
+       mmc_of_parse_timing_phase(dev, "clk-phase-uhs-sdr50",
+                                 &map[MMC_TIMING_UHS_SDR50]);
+       mmc_of_parse_timing_phase(dev, "clk-phase-uhs-sdr104",
+                                 &map[MMC_TIMING_UHS_SDR104]);
+       mmc_of_parse_timing_phase(dev, "clk-phase-uhs-ddr50",
+                                 &map[MMC_TIMING_UHS_DDR50]);
+       mmc_of_parse_timing_phase(dev, "clk-phase-mmc-ddr52",
+                                 &map[MMC_TIMING_MMC_DDR52]);
+       mmc_of_parse_timing_phase(dev, "clk-phase-mmc-hs200",
+                                 &map[MMC_TIMING_MMC_HS200]);
+       mmc_of_parse_timing_phase(dev, "clk-phase-mmc-hs400",
+                                 &map[MMC_TIMING_MMC_HS400]);
+}
+EXPORT_SYMBOL(mmc_of_parse_clk_phase);
+
 /**
  *     mmc_of_parse() - parse host's device-tree node
  *     @host: host whose node should be parsed.

diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 01bba36545c5..bc4731c9738f 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h

@@ -79,6 +79,22 @@ struct mmc_ios {
        bool enhanced_strobe;                   /* hs400es selection */
 };

+struct mmc_clk_phase {
+       bool valid;
+       u16 in_deg;
+       u16 out_deg;
+};
+
+/*
+ * Define a type to map between bus timings and phase correction values. To
+ * avoid bloat in struct mmc_host we leave it to the host driver to define the
+ * phase map object in its private data if it supports phase correction.
+ * However, mmc_of_parse_clk_phase() is provided by the mmc core and needs the
+ * provided array to be correctly sized, so typedef an appropriately sized
+ * array to minimise the chance that the wrong size object is passed.
+ */
+typedef struct mmc_clk_phase mmc_clk_phase_map_t[MMC_TIMING_MMC_HS400 + 1];
+