[PATCH v4] 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.
This is normally good enough to complete the request, 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

v3:
 - Use 'if-else' instead of 'goto'
 - Don't touch response field when maximize data field

v4:
 - Prevent 32bit divider overflow by splitting the operation
 - Changed %06x to %#08x as suggested by Doug
 - Rephrased commit msg as suggested by Doug

 drivers/mmc/host/dw_mmc.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
index d977f34f6b55..8e9d33e1b96c 100644
--- a/drivers/mmc/host/dw_mmc.c
+++ b/drivers/mmc/host/dw_mmc.c
@@ -1283,6 +1283,32 @@ 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);
+	tmp = DIV_ROUND_UP(tmp, clk_div);
+
+	/* TMOUT[7:0] (RESPONSE_TIMEOUT) */
+	tmout = 0xFF; /* Set maximum */
+
+	/* TMOUT[31:8] (DATA_TIMEOUT) */
+	if (!tmp || tmp > 0xFFFFFF)
+		tmout |= (0xFFFFFF << 8);
+	else
+		tmout |= (tmp & 0xFFFFFF) << 8;
+
+	mci_writel(host, TMOUT, tmout);
+	dev_dbg(host->dev, "timeout_ns: %u => TMOUT[31:8]: 0x%#08x",
+		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 +1329,7 @@ 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