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path: root/drivers/mmc/host/dw_mmc-rockchip.c
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Diffstat (limited to 'drivers/mmc/host/dw_mmc-rockchip.c')
-rw-r--r--drivers/mmc/host/dw_mmc-rockchip.c72
1 files changed, 68 insertions, 4 deletions
diff --git a/drivers/mmc/host/dw_mmc-rockchip.c b/drivers/mmc/host/dw_mmc-rockchip.c
index 8c20b81cafd8..358b0dc853b0 100644
--- a/drivers/mmc/host/dw_mmc-rockchip.c
+++ b/drivers/mmc/host/dw_mmc-rockchip.c
@@ -66,6 +66,70 @@ static void dw_mci_rk3288_set_ios(struct dw_mci *host, struct mmc_ios *ios)
/* Make sure we use phases which we can enumerate with */
if (!IS_ERR(priv->sample_clk))
clk_set_phase(priv->sample_clk, priv->default_sample_phase);
+
+ /*
+ * Set the drive phase offset based on speed mode to achieve hold times.
+ *
+ * NOTE: this is _not_ a value that is dynamically tuned and is also
+ * _not_ a value that will vary from board to board. It is a value
+ * that could vary between different SoC models if they had massively
+ * different output clock delays inside their dw_mmc IP block (delay_o),
+ * but since it's OK to overshoot a little we don't need to do complex
+ * calculations and can pick values that will just work for everyone.
+ *
+ * When picking values we'll stick with picking 0/90/180/270 since
+ * those can be made very accurately on all known Rockchip SoCs.
+ *
+ * Note that these values match values from the DesignWare Databook
+ * tables for the most part except for SDR12 and "ID mode". For those
+ * two modes the databook calculations assume a clock in of 50MHz. As
+ * seen above, we always use a clock in rate that is exactly the
+ * card's input clock (times RK3288_CLKGEN_DIV, but that gets divided
+ * back out before the controller sees it).
+ *
+ * From measurement of a single device, it appears that delay_o is
+ * about .5 ns. Since we try to leave a bit of margin, it's expected
+ * that numbers here will be fine even with much larger delay_o
+ * (the 1.4 ns assumed by the DesignWare Databook would result in the
+ * same results, for instance).
+ */
+ if (!IS_ERR(priv->drv_clk)) {
+ int phase;
+
+ /*
+ * In almost all cases a 90 degree phase offset will provide
+ * sufficient hold times across all valid input clock rates
+ * assuming delay_o is not absurd for a given SoC. We'll use
+ * that as a default.
+ */
+ phase = 90;
+
+ switch (ios->timing) {
+ case MMC_TIMING_MMC_DDR52:
+ /*
+ * Since clock in rate with MMC_DDR52 is doubled when
+ * bus width is 8 we need to double the phase offset
+ * to get the same timings.
+ */
+ if (ios->bus_width == MMC_BUS_WIDTH_8)
+ phase = 180;
+ break;
+ case MMC_TIMING_UHS_SDR104:
+ case MMC_TIMING_MMC_HS200:
+ /*
+ * In the case of 150 MHz clock (typical max for
+ * Rockchip SoCs), 90 degree offset will add a delay
+ * of 1.67 ns. That will meet min hold time of .8 ns
+ * as long as clock output delay is < .87 ns. On
+ * SoCs measured this seems to be OK, but it doesn't
+ * hurt to give margin here, so we use 180.
+ */
+ phase = 180;
+ break;
+ }
+
+ clk_set_phase(priv->drv_clk, phase);
+ }
}
#define NUM_PHASES 360
@@ -233,10 +297,10 @@ static int dw_mci_rockchip_init(struct dw_mci *host)
/* Common capabilities of RK3288 SoC */
static unsigned long dw_mci_rk3288_dwmmc_caps[4] = {
- MMC_CAP_ERASE,
- MMC_CAP_ERASE,
- MMC_CAP_ERASE,
- MMC_CAP_ERASE,
+ MMC_CAP_ERASE | MMC_CAP_CMD23,
+ MMC_CAP_ERASE | MMC_CAP_CMD23,
+ MMC_CAP_ERASE | MMC_CAP_CMD23,
+ MMC_CAP_ERASE | MMC_CAP_CMD23,
};
static const struct dw_mci_drv_data rk2928_drv_data = {