mmc: mediatek: add latch-ck support

some platform(eg.mt2701) does not support "stop clk fix", in
this case, need set correct latch-ck to avoid crc error caused
by stop clock block-internally.
Signed-off-by: NChaotian Jing <chaotian.jing@mediatek.com>
Tested-by: NSean Wang <sean.wang@mediatek.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/mtk-sd.c

@@ -378,6 +378,7 @@ struct msdc_host {
 	u32 sclk;		/* SD/MS bus clock frequency */
 	unsigned char timing;
 	bool vqmmc_enabled;
+	u32 latch_ck;
 	u32 hs400_ds_delay;
 	u32 hs200_cmd_int_delay; /* cmd internal delay for HS200/SDR104 */
 	u32 hs400_cmd_int_delay; /* cmd internal delay for HS400 */
@@ -1661,6 +1662,8 @@ static int msdc_tune_data(struct mmc_host *mmc, u32 opcode)
 	u32 tune_reg = host->dev_comp->pad_tune_reg;
 	int i, ret;
 
+	sdr_set_field(host->base + MSDC_PATCH_BIT, MSDC_INT_DAT_LATCH_CK_SEL,
+		      host->latch_ck);
 	sdr_clr_bits(host->base + MSDC_IOCON, MSDC_IOCON_DSPL);
 	sdr_clr_bits(host->base + MSDC_IOCON, MSDC_IOCON_W_DSPL);
 	for (i = 0 ; i < PAD_DELAY_MAX; i++) {
@@ -1773,6 +1776,9 @@ static const struct mmc_host_ops mt_msdc_ops = {
 static void msdc_of_property_parse(struct platform_device *pdev,
 				   struct msdc_host *host)
 {
+	of_property_read_u32(pdev->dev.of_node, "mediatek,latch-ck",
+			     &host->latch_ck);
+
 	of_property_read_u32(pdev->dev.of_node, "hs400-ds-delay",
 			     &host->hs400_ds_delay);