[PATCH v2] mmc: dw_mmc: Allow lower TMOUT value than maximum

["Mårten Lindahl" <marten.lindahl@axis.com>]

The TMOUT register is always set with a full value for every transfer,
which (with a 200MHz clock) will give a full DRTO of ~84 milliseconds.
Since the software dto_timer acts as a backup in cases when this timeout
is not long enough, it is normally not a problem. But setting a full
value makes it impossible to test shorter timeouts, when for example
testing data read times on different SD cards.

Add a function to set any value smaller than the maximum of 0xFFFFFF.

Signed-off-by: Mårten Lindahl <marten.lindahl@axis.com>
---

v2:
 - Calculate new value before checking boundaries
 - Include CLKDIV register to get proper value

 drivers/mmc/host/dw_mmc.c | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index 6578cc64ae9e..6edd7a231448 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -1283,6 +1283,36 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)
 	mci_writel(host, CTYPE, (slot->ctype << slot->id));
 }
 
+static void dw_mci_set_data_timeout(struct dw_mci *host,
+				    unsigned int timeout_ns)
+{
+	unsigned int clk_div, tmp, tmout;
+
+	clk_div = (mci_readl(host, CLKDIV) & 0xFF) * 2;
+	if (clk_div == 0)
+		clk_div = 1;
+
+	tmp = DIV_ROUND_UP_ULL((u64)timeout_ns * host->bus_hz,
+			       NSEC_PER_SEC * clk_div);
+
+	if (!tmp || tmp > 0xFFFFFF) {
+		/* Set maximum */
+		tmout = 0xFFFFFFFF;
+		goto tmout_done;
+	}
+
+	/* TMOUT[7:0] (RESPONSE_TIMEOUT) */
+	tmout = 0xFF; /* Set maximum */
+
+	/* TMOUT[31:8] (DATA_TIMEOUT) */
+	tmout |= (tmp & 0xFFFFFF) << 8;
+
+tmout_done:
+	mci_writel(host, TMOUT, tmout);
+	dev_dbg(host->dev, "timeout_ns: %u => TMOUT[31:8]: 0x%06x",
+		timeout_ns, tmout >> 8);
+}
+
 static void __dw_mci_start_request(struct dw_mci *host,
 				   struct dw_mci_slot *slot,
 				   struct mmc_command *cmd)
@@ -1303,7 +1333,7 @@ static void __dw_mci_start_request(struct dw_mci *host,
 
 	data = cmd->data;
 	if (data) {
-		mci_writel(host, TMOUT, 0xFFFFFFFF);
+		dw_mci_set_data_timeout(host, data->timeout_ns);
 		mci_writel(host, BYTCNT, data->blksz*data->blocks);
 		mci_writel(host, BLKSIZ, data->blksz);
 	}
-- 
2.20.1