Re: [PATCH] mmc: sdhci-omap: Workaround errata regarding SDR104/HS200 tuning failures (i929)
From: Kishon Vijay Abraham I
Date: Thu Nov 29 2018 - 23:41:05 EST
Hi Faiz,
On 30/11/18 12:35 AM, Faiz Abbas wrote:
> Errata i929 in certain OMAP5/DRA7XX/AM57XX silicon revisions
> (SPRZ426D - November 2014 - Revised February 2018 [1]) mentions
> unexpected tuning pattern errors. A small failure band may be present
> in the tuning range which may be missed by the current algorithm.
> Furthermore, the failure bands vary with temperature leading to
> different optimum tuning values for different temperatures.
>
> As suggested in the related Application Report (SPRACA9B - October 2017
> - Revised July 2018 [2]), tuning should be done in two stages.
> In stage 1, assign the optimum ratio in the maximum pass window for the
> current temperature. In stage 2, if the chosen value is close to the
> small failure band, move away from it in the appropriate direction.
>
> References:
> [1] http://www.ti.com/lit/pdf/sprz426
> [2] http://www.ti.com/lit/pdf/SPRACA9
>
> Signed-off-by: Faiz Abbas <faiz_abbas@xxxxxx>
> ---
> drivers/mmc/host/Kconfig | 2 +
> drivers/mmc/host/sdhci-omap.c | 90 ++++++++++++++++++++++++++++++++++-
> 2 files changed, 91 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
> index 1b58739d9744..6d3553f06f27 100644
> --- a/drivers/mmc/host/Kconfig
> +++ b/drivers/mmc/host/Kconfig
> @@ -969,6 +969,8 @@ config MMC_SDHCI_XENON
> config MMC_SDHCI_OMAP
> tristate "TI SDHCI Controller Support"
> depends on MMC_SDHCI_PLTFM && OF
> + select THERMAL
> + select TI_SOC_THERMAL
> help
> This selects the Secure Digital Host Controller Interface (SDHCI)
> support present in TI's DRA7 SOCs. The controller supports
> diff --git a/drivers/mmc/host/sdhci-omap.c b/drivers/mmc/host/sdhci-omap.c
> index b3cb39d0db6f..9ccce7ef3a60 100644
> --- a/drivers/mmc/host/sdhci-omap.c
> +++ b/drivers/mmc/host/sdhci-omap.c
> @@ -27,6 +27,7 @@
> #include <linux/regulator/consumer.h>
> #include <linux/pinctrl/consumer.h>
> #include <linux/sys_soc.h>
> +#include <linux/thermal.h>
>
> #include "sdhci-pltfm.h"
>
> @@ -286,14 +287,18 @@ static int sdhci_omap_execute_tuning(struct mmc_host *mmc, u32 opcode)
> struct sdhci_host *host = mmc_priv(mmc);
> struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
> struct sdhci_omap_host *omap_host = sdhci_pltfm_priv(pltfm_host);
> + struct thermal_zone_device *thermal_dev;
> struct device *dev = omap_host->dev;
> struct mmc_ios *ios = &mmc->ios;
> u32 start_window = 0, max_window = 0;
> + bool single_point_failure = false;
> u8 cur_match, prev_match = 0;
> u32 length = 0, max_len = 0;
> u32 phase_delay = 0;
> + int temperature;
> int ret = 0;
> u32 reg;
> + int i;
>
> /* clock tuning is not needed for upto 52MHz */
> if (ios->clock <= 52000000)
> @@ -303,6 +308,16 @@ static int sdhci_omap_execute_tuning(struct mmc_host *mmc, u32 opcode)
> if (ios->timing == MMC_TIMING_UHS_SDR50 && !(reg & CAPA2_TSDR50))
> return 0;
>
> + thermal_dev = thermal_zone_get_zone_by_name("cpu_thermal");
> + if (IS_ERR(thermal_dev)) {
> + dev_err(dev, "Unable to get thermal zone for tuning\n");
> + return PTR_ERR(thermal_dev);
> + }
Can't we get thermal zone once during probe?
Thanks
Kishon
> +
> + ret = thermal_zone_get_temp(thermal_dev, &temperature);
> + if (ret)
> + return ret;
> +
> reg = sdhci_omap_readl(omap_host, SDHCI_OMAP_DLL);
> reg |= DLL_SWT;
> sdhci_omap_writel(omap_host, SDHCI_OMAP_DLL, reg);
> @@ -317,6 +332,11 @@ static int sdhci_omap_execute_tuning(struct mmc_host *mmc, u32 opcode)
>
> omap_host->is_tuning = true;
>
> + /*
> + * Stage 1: Search for a maximum pass window ignoring any
> + * any single point failures. If the tuning value ends up
> + * near it, move away from it in stage 2 below
> + */
> while (phase_delay <= MAX_PHASE_DELAY) {
> sdhci_omap_set_dll(omap_host, phase_delay);
>
> @@ -324,10 +344,15 @@ static int sdhci_omap_execute_tuning(struct mmc_host *mmc, u32 opcode)
> if (cur_match) {
> if (prev_match) {
> length++;
> + } else if (single_point_failure) {
> + /* ignore single point failure */
> + length++;
> } else {
> start_window = phase_delay;
> length = 1;
> }
> + } else {
> + single_point_failure = prev_match;
> }
>
> if (length > max_len) {
> @@ -345,13 +370,76 @@ static int sdhci_omap_execute_tuning(struct mmc_host *mmc, u32 opcode)
> goto tuning_error;
> }
>
> + /*
> + * Assign tuning value as a ratio of maximum pass window based
> + * on temperature
> + */
> + if (temperature < -20000)
> + phase_delay = min(max_window + 4 * max_len - 24,
> + max_window +
> + DIV_ROUND_UP(13 * max_len, 16) * 4);
> + else if (temperature < 20000)
> + phase_delay = max_window + DIV_ROUND_UP(9 * max_len, 16) * 4;
> + else if (temperature < 40000)
> + phase_delay = max_window + DIV_ROUND_UP(8 * max_len, 16) * 4;
> + else if (temperature < 70000)
> + phase_delay = max_window + DIV_ROUND_UP(7 * max_len, 16) * 4;
> + else if (temperature < 90000)
> + phase_delay = max_window + DIV_ROUND_UP(5 * max_len, 16) * 4;
> + else if (temperature < 120000)
> + phase_delay = max_window + DIV_ROUND_UP(4 * max_len, 16) * 4;
> + else
> + phase_delay = max_window + DIV_ROUND_UP(3 * max_len, 16) * 4;
> +
> + /*
> + * Stage 2: Search for a single point failure near the chosen tuning
> + * value in two steps. First in the +3 to +10 range and then in the
> + * +2 to -10 range. If found, move away from it in the appropriate
> + * direction by the appropriate amount depending on the temperature.
> + */
> + for (i = 3; i <= 10; i++) {
> + sdhci_omap_set_dll(omap_host, phase_delay + i);
> +
> + if (mmc_send_tuning(mmc, opcode, NULL)) {
> + if (temperature < 10000)
> + phase_delay += i + 6;
> + else if (temperature < 20000)
> + phase_delay += i - 12;
> + else if (temperature < 70000)
> + phase_delay += i - 8;
> + else
> + phase_delay += i - 6;
> +
> + goto single_failure_found;
> + }
> + }
> +
> + for (i = 2; i >= -10; i--) {
> + sdhci_omap_set_dll(omap_host, phase_delay + i);
> +
> + if (mmc_send_tuning(mmc, opcode, NULL)) {
> + if (temperature < 10000)
> + phase_delay += i + 12;
> + else if (temperature < 20000)
> + phase_delay += i + 8;
> + else if (temperature < 70000)
> + phase_delay += i + 8;
> + else if (temperature < 90000)
> + phase_delay += i + 10;
> + else
> + phase_delay += i + 12;
> +
> + goto single_failure_found;
> + }
> + }
> +
> +single_failure_found:
> reg = sdhci_omap_readl(omap_host, SDHCI_OMAP_AC12);
> if (!(reg & AC12_SCLK_SEL)) {
> ret = -EIO;
> goto tuning_error;
> }
>
> - phase_delay = max_window + 4 * (max_len >> 1);
> sdhci_omap_set_dll(omap_host, phase_delay);
>
> omap_host->is_tuning = false;
>