mmc: jz4740: Inform the mmc core about the maximum busy timeout

Some commands uses R1B responses, which means the card may assert the DAT0
line to signal busy for a period of time, after it has received the
command. The mmc core normally specifies the busy period for the command in
the cmd->busy_timeout. Ideally the driver should respect it, but that
requires quite some update of the code, so let's defer that to someone with
the HW at hand.

Instead, let's inform the mmc core about the maximum supported busy timeout
in ->max_busy_timeout during ->probe(). This value corresponds to the fixed
5s timeout used by jz4740. In this way, we let the mmc core validate the
needed timeout, which may lead to that it converts from a R1B into a R1
response and then use CMD13 to poll for busy completion.

In other words, this change enables support for commands with longer busy
periods than 5s, like erase (CMD38) for example.

Cc: Paul Cercueil <paul@crapouillou.net>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20200414161413.3036-5-ulf.hansson@linaro.org

drivers/mmc/host/jz4740_mmc.c

@@ -108,6 +108,7 @@
 #define	JZ_MMC_LPM_LOW_POWER_MODE_EN BIT(0)
 
 #define JZ_MMC_CLK_RATE 24000000
+#define JZ_MMC_REQ_TIMEOUT_MS 5000
 
 enum jz4740_mmc_version {
 	JZ_MMC_JZ4740,
@@ -440,7 +441,8 @@ static unsigned int jz4740_mmc_poll_irq(struct jz4740_mmc_host *host,
 
 	if (timeout == 0) {
 		set_bit(0, &host->waiting);
-		mod_timer(&host->timeout_timer, jiffies + 5*HZ);
+		mod_timer(&host->timeout_timer,
+			  jiffies + msecs_to_jiffies(JZ_MMC_REQ_TIMEOUT_MS));
 		jz4740_mmc_set_irq_enabled(host, irq, true);
 		return true;
 	}
@@ -893,7 +895,8 @@ static void jz4740_mmc_request(struct mmc_host *mmc, struct mmc_request *req)
 
 	host->state = JZ4740_MMC_STATE_READ_RESPONSE;
 	set_bit(0, &host->waiting);
-	mod_timer(&host->timeout_timer, jiffies + 5*HZ);
+	mod_timer(&host->timeout_timer,
+		  jiffies + msecs_to_jiffies(JZ_MMC_REQ_TIMEOUT_MS));
 	jz4740_mmc_send_command(host, req->cmd);
 }
 
@@ -1023,6 +1026,12 @@ static int jz4740_mmc_probe(struct platform_device* pdev)
 	mmc->f_min = mmc->f_max / 128;
 	mmc->ocr_avail = MMC_VDD_32_33 | MMC_VDD_33_34;
 
+	/*
+	 * We use a fixed timeout of 5s, hence inform the core about it. A
+	 * future improvement should instead respect the cmd->busy_timeout.
+	 */
+	mmc->max_busy_timeout = JZ_MMC_REQ_TIMEOUT_MS;
+
 	mmc->max_blk_size = (1 << 10) - 1;
 	mmc->max_blk_count = (1 << 15) - 1;
 	mmc->max_req_size = mmc->max_blk_size * mmc->max_blk_count;