mmc: sdhci-esdhc-imx: optimize the manual tuing logic to get the best timing

Current manual tuning logic only get the first pass window, but
this pass window maybe not the best pass window.

Now find all the pass window, and chose the largest pass window,
and use the average value of this largest pass window to get the
best timing.

Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20230831032647.3128702-1-haibo.chen@nxp.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
index 3b8030f3552af821311e9b5fce1dbf04013ca271..40a6e2f8145a114feda347d86b0ebf6039c370b4 100644 (file)
--- a/drivers/mmc/host/sdhci-esdhc-imx.c
+++ b/drivers/mmc/host/sdhci-esdhc-imx.c
@@ -1154,32 +1154,52 @@ static void esdhc_post_tuning(struct sdhci_host *host)
        writel(reg, host->ioaddr + ESDHC_MIX_CTRL);
 }
 
+/*
+ * find the largest pass window, and use the average delay of this
+ * largest window to get the best timing.
+ */
 static int esdhc_executing_tuning(struct sdhci_host *host, u32 opcode)
 {
        int min, max, avg, ret;
+       int win_length, target_min, target_max, target_win_length;
 
-       /* find the mininum delay first which can pass tuning */
        min = ESDHC_TUNE_CTRL_MIN;
-       while (min < ESDHC_TUNE_CTRL_MAX) {
-               esdhc_prepare_tuning(host, min);
-               if (!mmc_send_tuning(host->mmc, opcode, NULL))
-                       break;
-               min += ESDHC_TUNE_CTRL_STEP;
-       }
-
-       /* find the maxinum delay which can not pass tuning */
-       max = min + ESDHC_TUNE_CTRL_STEP;
+       max = ESDHC_TUNE_CTRL_MIN;
+       target_win_length = 0;
        while (max < ESDHC_TUNE_CTRL_MAX) {
-               esdhc_prepare_tuning(host, max);
-               if (mmc_send_tuning(host->mmc, opcode, NULL)) {
-                       max -= ESDHC_TUNE_CTRL_STEP;
-                       break;
+               /* find the mininum delay first which can pass tuning */
+               while (min < ESDHC_TUNE_CTRL_MAX) {
+                       esdhc_prepare_tuning(host, min);
+                       if (!mmc_send_tuning(host->mmc, opcode, NULL))
+                               break;
+                       min += ESDHC_TUNE_CTRL_STEP;
                }
-               max += ESDHC_TUNE_CTRL_STEP;
+
+               /* find the maxinum delay which can not pass tuning */
+               max = min + ESDHC_TUNE_CTRL_STEP;
+               while (max < ESDHC_TUNE_CTRL_MAX) {
+                       esdhc_prepare_tuning(host, max);
+                       if (mmc_send_tuning(host->mmc, opcode, NULL)) {
+                               max -= ESDHC_TUNE_CTRL_STEP;
+                               break;
+                       }
+                       max += ESDHC_TUNE_CTRL_STEP;
+               }
+
+               win_length = max - min + 1;
+               /* get the largest pass window */
+               if (win_length > target_win_length) {
+                       target_win_length = win_length;
+                       target_min = min;
+                       target_max = max;
+               }
+
+               /* continue to find the next pass window */
+               min = max + ESDHC_TUNE_CTRL_STEP;
        }
 
        /* use average delay to get the best timing */
-       avg = (min + max) / 2;
+       avg = (target_min + target_max) / 2;
        esdhc_prepare_tuning(host, avg);
        ret = mmc_send_tuning(host->mmc, opcode, NULL);
        esdhc_post_tuning(host);