sunxi: mmc: Properly setup mod-clk and clock sampling phases

The sunxi mmc controller has both an internal clock divider, as well as
the divider in the mod0-clk for the mmc controller.

The internal divider cannot be used, as it conflicts with the setting of
clock sampling phases which is done in the mod0-clk, so it must be set to
0 (divide by 1).

For some reason while the kernel has had this correct from day one, the
u-boot sunxi mmc code has been using a fixed mod0-clk and setting its
internal divider depending on the desired speed. This is something which
we've inherited from the original Allwinner u-boot sources, but while this
has been fixed in Allwinner's own u-boot code at least for the A23 and later
upstream u-boot was still doing this wrong.

This commit fixes this, thereby also fixing mmc support not working reliable
on the A23 (which seems more sensitive to this) and possible also fixes some
other sunxi mmc issues.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>

1 files changed, 68 insertions, 27 deletions

diff --git a/drivers/mmc/sunxi_mmc.c b/drivers/mmc/sunxi_mmc.c
index 231f0a0..20d18d0 100644
--- a/drivers/mmc/sunxi_mmc.c
+++ b/drivers/mmc/sunxi_mmc.c
@@ -22,7 +22,6 @@ struct sunxi_mmc_host {
 	unsigned mmc_no;
 	uint32_t *mclkreg;
 	unsigned fatal_err;
-	unsigned mod_clk;
 	struct sunxi_mmc *reg;
 	struct mmc_config cfg;
 };
@@ -79,10 +78,63 @@ static int mmc_resource_init(int sdc_no)
 	return ret;
 }
 
+static int mmc_set_mod_clk(struct sunxi_mmc_host *mmchost, unsigned int hz)
+{
+	unsigned int pll, pll_hz, div, n, oclk_dly, sclk_dly;
+
+	if (hz <= 24000000) {
+		pll = CCM_MMC_CTRL_OSCM24;
+		pll_hz = 24000000;
+	} else {
+		pll = CCM_MMC_CTRL_PLL6;
+		pll_hz = clock_get_pll6();
+	}
+
+	div = pll_hz / hz;
+	if (pll_hz % hz)
+		div++;
+
+	n = 0;
+	while (div > 16) {
+		n++;
+		div = (div + 1) / 2;
+	}
+
+	if (n > 3) {
+		printf("mmc %u error cannot set clock to %u\n",
+		       mmchost->mmc_no, hz);
+		return -1;
+	}
+
+	/* determine delays */
+	if (hz <= 400000) {
+		oclk_dly = 0;
+		sclk_dly = 7;
+	} else if (hz <= 25000000) {
+		oclk_dly = 0;
+		sclk_dly = 5;
+	} else if (hz <= 50000000) {
+		oclk_dly = 3;
+		sclk_dly = 5;
+	} else {
+		/* hz > 50000000 */
+		oclk_dly = 2;
+		sclk_dly = 4;
+	}
+
+	writel(CCM_MMC_CTRL_ENABLE | pll | CCM_MMC_CTRL_SCLK_DLY(sclk_dly) |
+	       CCM_MMC_CTRL_N(n) | CCM_MMC_CTRL_OCLK_DLY(oclk_dly) |
+	       CCM_MMC_CTRL_M(div), mmchost->mclkreg);
+
+	debug("mmc %u set mod-clk req %u parent %u n %u m %u rate %u\n",
+	      mmchost->mmc_no, hz, pll_hz, 1u << n, div,
+	      pll_hz / (1u << n) / div);
+
+	return 0;
+}
+
 static int mmc_clk_io_on(int sdc_no)
 {
-	unsigned int pll_clk;
-	unsigned int divider;
 	struct sunxi_mmc_host *mmchost = &mmc_host[sdc_no];
 	struct sunxi_ccm_reg *ccm = (struct sunxi_ccm_reg *)SUNXI_CCM_BASE;
 
@@ -96,15 +148,7 @@ static int mmc_clk_io_on(int sdc_no)
 	setbits_le32(&ccm->ahb_reset0_cfg, 1 << AHB_RESET_OFFSET_MMC(sdc_no));
 #endif
 
-	/* config mod clock */
-	pll_clk = clock_get_pll6();
-	/* should be close to 100 MHz but no more, so round up */
-	divider = ((pll_clk + 99999999) / 100000000) - 1;
-	writel(CCM_MMC_CTRL_ENABLE | CCM_MMC_CTRL_PLL6 | divider,
-	       mmchost->mclkreg);
-	mmchost->mod_clk = pll_clk / (divider + 1);
-
-	return 0;
+	return mmc_set_mod_clk(mmchost, 24000000);
 }
 
 static int mmc_update_clk(struct mmc *mmc)
@@ -129,7 +173,7 @@ static int mmc_update_clk(struct mmc *mmc)
 	return 0;
 }
 
-static int mmc_config_clock(struct mmc *mmc, unsigned div)
+static int mmc_config_clock(struct mmc *mmc)
 {
 	struct sunxi_mmc_host *mmchost = mmc->priv;
 	unsigned rval = readl(&mmchost->reg->clkcr);
@@ -140,16 +184,17 @@ static int mmc_config_clock(struct mmc *mmc, unsigned div)
 	if (mmc_update_clk(mmc))
 		return -1;
 
-	/* Change Divider Factor */
+	/* Set mod_clk to new rate */
+	if (mmc_set_mod_clk(mmchost, mmc->clock))
+		return -1;
+
+	/* Clear internal divider */
 	rval &= ~SUNXI_MMC_CLK_DIVIDER_MASK;
-	rval |= div;
 	writel(rval, &mmchost->reg->clkcr);
-	if (mmc_update_clk(mmc))
-		return -1;
+
 	/* Re-enable Clock */
 	rval |= SUNXI_MMC_CLK_ENABLE;
 	writel(rval, &mmchost->reg->clkcr);
-
 	if (mmc_update_clk(mmc))
 		return -1;
 
@@ -159,18 +204,14 @@ static int mmc_config_clock(struct mmc *mmc, unsigned div)
 static void mmc_set_ios(struct mmc *mmc)
 {
 	struct sunxi_mmc_host *mmchost = mmc->priv;
-	unsigned int clkdiv = 0;
 
-	debug("set ios: bus_width: %x, clock: %d, mod_clk: %d\n",
-	      mmc->bus_width, mmc->clock, mmchost->mod_clk);
+	debug("set ios: bus_width: %x, clock: %d\n",
+	      mmc->bus_width, mmc->clock);
 
 	/* Change clock first */
-	clkdiv = (mmchost->mod_clk + (mmc->clock >> 1)) / mmc->clock / 2;
-	if (mmc->clock) {
-		if (mmc_config_clock(mmc, clkdiv)) {
-			mmchost->fatal_err = 1;
-			return;
-		}
+	if (mmc->clock && mmc_config_clock(mmc) != 0) {
+		mmchost->fatal_err = 1;
+		return;
 	}
 
 	/* Change bus width */