mmc: dw_mmc: Allow lower TMOUT value than maximum

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>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
Link: https://lore.kernel.org/r/20211119155337.14341-1-marten.lindahl@axis.comSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/dw_mmc.c

@@ -1284,6 +1284,33 @@ 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)
+{
+	u32 clk_div, tmout;
+	u64 tmp;
+
+	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_ULL(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)
@@ -1304,7 +1331,7 @@ 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);
 	}