[PATCH v2 1/3] mmc: k1: handle a missing max-frequency and clk_set_rate()'s return value

[Dave Klotz]

The driver sets the io clock to the max-frequency the device tree gives
and fails the probe on any non-zero return from clk_set_rate(). Two
problems follow:

- clk_set_rate() returns the new rate on success and a negative error
  code on failure. The SpacemiT clock driver happens to return 0, but
  any clock driver that reports the rate makes the probe fail.
- A node without max-frequency asks for 0 Hz. On the K1 clock driver
  that picks no divider at all and writes whatever the calculation left
  behind into the io clock's divider field; host->max_clk is then 0,
  the capabilities register gives no base clock either, and the probe
  fails in sdhci_setup_cfg().

Treat only a negative return as an error. Without max-frequency, leave
the io clock as an earlier stage set it and run from its current rate.

Signed-off-by: Dave Klotz <davewk...@protonmail.com>

Changes in v2:
- Use ulong and IS_ERR_VALUE() for the clock API return values.
- Validate clk_get_rate() before narrowing to cfg.f_max and retain the error.

---
 drivers/mmc/spacemit_sdhci.c | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/spacemit_sdhci.c b/drivers/mmc/spacemit_sdhci.c
index f5578f38bd..6488ae0fdb 100644
--- a/drivers/mmc/spacemit_sdhci.c
+++ b/drivers/mmc/spacemit_sdhci.c
@@ -606,10 +606,30 @@
                goto err_reset;
        }
 
-       ret = clk_set_rate(&clk, plat->cfg.f_max);
-       if (ret) {
-               log_err("Failed to set io clk: %d\n", ret);
-               goto err_reset;
+       /*
+        * Without max-frequency there is no rate to ask for: leave the io
+        * clock as an earlier stage set it and run from its current rate. The
+        * capabilities register gives no base clock on the K1, so it cannot
+        * stand in. clk_set_rate() returns the new rate on success, so only a
+        * negative value is an error.
+        */
+       if (plat->cfg.f_max) {
+               ulong rate = clk_set_rate(&clk, plat->cfg.f_max);
+
+               if (IS_ERR_VALUE(rate)) {
+                       ret = (int)rate;
+                       log_err("Failed to set io clk: %d\n", ret);
+                       goto err_reset;
+               }
+       } else {
+               ulong rate = clk_get_rate(&clk);
+
+               if (IS_ERR_VALUE(rate) || !rate) {
+                       ret = rate ? (int)rate : -EINVAL;
+                       log_err("No max-frequency and no io clk rate\n");
+                       goto err_reset;
+               }
+               plat->cfg.f_max = rate;
        }
 
        /* Set quirks */
-- 
2.55.0