mmc: sdhci: SD tuning is broken for some controllers (7ce45e95) · Commits · 戴 / test

The SD Host Controller spec states that the SD Host Controller can request that the driver send up to 40 CMD19's while doing tuning and that the total time the card spends responding must be < 150ms. The sdhci_execute_tuning() function in sdhci.c that loops through sending the CMD19's has multiple bugs. First it sets a "timeout" variable to 150 and a loop counter variable to 40. It then decrements both variables by 1 at the end of each loop. It tries to handle violations of the count and time by doing a break when BOTH variables are equal to zero, which can never happen because they we set to different values and decremented by 1 at the same time. The timeout variable is not based on time at all and is totally useless. The routine also considers a loop counter of zero to be an error which means that any controller that requests the max of 40 CMD19s will cause tuning to fail and be disabled. I've fixed these issues by allowing up to 40 CMD19's and I've removed any attempt to handle the 150ms time limit. Removing timeout checking seems safe here because each CMD19 is timeout protected and the max loop counters insures we don't loop forever. Adding timeout checking would not be as simple as snapping the time at the loop start and checking for 150ms to pass because the loop queues the CMD19's and uses events to wait for completion so the time would include all the normal scheduler latencies. Signed-off-by:

Al Cooper <alcooperx@gmail.com> Signed-off-by:

Ulf Hansson <ulf.hansson@linaro.org> Signed-off-by:

Chris Ball <chris@printf.net>

drivers/mmc/host/sdhci.c

+9 −15

Original line number	Diff line number	Diff line
		@@ -1823,7 +1823,6 @@ static int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode)
		struct sdhci_host *host = mmc_priv(mmc);
		u16 ctrl;
		int tuning_loop_counter = MAX_TUNING_LOOP;
		unsigned long timeout;
		int err = 0;
		unsigned long flags;

		@@ -1882,14 +1881,10 @@ static int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode)
		* Issue CMD19 repeatedly till Execute Tuning is set to 0 or the number
		* of loops reaches 40 times or a timeout of 150ms occurs.
		*/
		timeout = 150;
		do {
		struct mmc_command cmd = {0};
		struct mmc_request mrq = {NULL};

		if (!tuning_loop_counter && !timeout)
		break;

		cmd.opcode = opcode;
		cmd.arg = 0;
		cmd.flags = MMC_RSP_R1 \| MMC_CMD_ADTC;
		@@ -1897,6 +1892,9 @@ static int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode)
		cmd.data = NULL;
		cmd.error = 0;

		if (tuning_loop_counter-- == 0)
		break;

		mrq.cmd = &cmd;
		host->mrq = &mrq;

		@@ -1954,8 +1952,6 @@ static int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode)
		host->tuning_done = 0;

		ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
		tuning_loop_counter--;
		timeout--;

		/* eMMC spec does not require a delay between tuning cycles */
		if (opcode == MMC_SEND_TUNING_BLOCK)
		@@ -1966,18 +1962,16 @@ static int sdhci_execute_tuning(struct mmc_host *mmc, u32 opcode)
		* The Host Driver has exhausted the maximum number of loops allowed,
		* so use fixed sampling frequency.
		*/
		if (!tuning_loop_counter \|\| !timeout) {
		if (tuning_loop_counter < 0) {
		ctrl &= ~SDHCI_CTRL_TUNED_CLK;
		sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
		err = -EIO;
		} else {
		}
		if (!(ctrl & SDHCI_CTRL_TUNED_CLK)) {
		pr_info(DRIVER_NAME ": Tuning procedure"
		" failed, falling back to fixed sampling"
		" clock\n");
		err = -EIO;
		}
		}

		out:
		/*

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