atmel_mci: Fix data timeout value

Calculate the data timeout based on values from the CSD instead of
just using a hardcoded DTOR value. This is a backport of a similar fix
in BSP 2.0, with one additional fix: the DTOCYC value is rounded up
instead of down.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>

diff --git a/cpu/at32ap/atmel_mci.c b/cpu/at32ap/atmel_mci.c
index bdca1c19f41a6144517c43456ee9c4e4b2940435..cf48be10ba4d44795aadef6afda5cdfa0df30f22 100644 (file)
--- a/cpu/at32ap/atmel_mci.c
+++ b/cpu/at32ap/atmel_mci.c
@@ -56,6 +56,7 @@
 #define MMC_DEFAULT_RCA                1
 
 static unsigned int mmc_rca;
+static int mmc_card_is_sd;
 static block_dev_desc_t mmc_blkdev;
 
 block_dev_desc_t *mmc_get_dev(int dev)
@@ -373,6 +374,7 @@ static int sd_init_card(struct mmc_cid *cid, int verbose)
        mmc_rca = resp[0] >> 16;
        if (verbose)
                printf("SD Card detected (RCA %u)\n", mmc_rca);
+       mmc_card_is_sd = 1;
        return 0;
 }
 
@@ -407,6 +409,59 @@ static int mmc_init_card(struct mmc_cid *cid, int verbose)
        return ret;
 }
 
+static void mci_set_data_timeout(struct mmc_csd *csd)
+{
+       static const unsigned int dtomul_to_shift[] = {
+               0, 4, 7, 8, 10, 12, 16, 20,
+       };
+       static const unsigned int taac_exp[] = {
+               1, 10, 100, 1000, 10000, 100000, 1000000, 10000000,
+       };
+       static const unsigned int taac_mant[] = {
+               0,  10, 12, 13, 15, 60, 25, 30,
+               35, 40, 45, 50, 55, 60, 70, 80,
+       };
+       unsigned int timeout_ns, timeout_clks;
+       unsigned int e, m;
+       unsigned int dtocyc, dtomul;
+       unsigned int shift;
+       u32 dtor;
+
+       e = csd->taac & 0x07;
+       m = (csd->taac >> 3) & 0x0f;
+
+       timeout_ns = (taac_exp[e] * taac_mant[m] + 9) / 10;
+       timeout_clks = csd->nsac * 100;
+
+       timeout_clks += (((timeout_ns + 9) / 10)
+                        * ((CFG_MMC_CLK_PP + 99999) / 100000) + 9999) / 10000;
+       if (!mmc_card_is_sd)
+               timeout_clks *= 10;
+       else
+               timeout_clks *= 100;
+
+       dtocyc = timeout_clks;
+       dtomul = 0;
+       while (dtocyc > 15 && dtomul < 8) {
+               dtomul++;
+               shift = dtomul_to_shift[dtomul];
+               dtocyc = (timeout_clks + (1 << shift) - 1) >> shift;
+       }
+
+       if (dtomul >= 8) {
+               dtomul = 7;
+               dtocyc = 15;
+               puts("Warning: Using maximum data timeout\n");
+       }
+
+       dtor = (MMCI_BF(DTOMUL, dtomul)
+               | MMCI_BF(DTOCYC, dtocyc));
+       mmci_writel(DTOR, dtor);
+
+       printf("mmc: Using %u cycles data timeout (DTOR=0x%x)\n",
+              dtocyc << shift, dtor);
+}
+
 int mmc_init(int verbose)
 {
        struct mmc_cid cid;
@@ -421,6 +476,8 @@ int mmc_init(int verbose)
        mmci_writel(IDR, ~0UL);
        mci_set_mode(CFG_MMC_CLK_OD, MMC_DEFAULT_BLKLEN);
 
+       mmc_card_is_sd = 0;
+
        ret = sd_init_card(&cid, verbose);
        if (ret) {
                mmc_rca = MMC_DEFAULT_RCA;
@@ -436,6 +493,8 @@ int mmc_init(int verbose)
        if (verbose)
                mmc_dump_csd(&csd);
 
+       mci_set_data_timeout(&csd);
+
        /* Initialize the blockdev structure */
        mmc_blkdev.if_type = IF_TYPE_MMC;
        mmc_blkdev.part_type = PART_TYPE_DOS;