Re: [PATCH v4 15/19] watchdog: s3c2410_wdt: Add support for WTCON register DBGACK_MASK bit

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On 11/21/23 09:52, Sam Protsenko wrote:
On Mon, Nov 20, 2023 at 3:21 PM Peter Griffin <peter.griffin@xxxxxxxxxx> wrote:

The WDT uses the CPU core signal DBGACK to determine whether the SoC
is running in debug mode or not. If the DBGACK signal is asserted and
DBGACK_MASK is enabled, then WDT output and interrupt is masked.

Presence of the DBGACK_MASK bit is determined by adding a new
QUIRK_HAS_DBGACK_BIT quirk. Currently only gs101 SoC is known to have
the DBGACK_MASK bit so add the quirk to drv_data_gs101_cl1 and
drv_data_gs101_cl1 quirks.

Signed-off-by: Peter Griffin <peter.griffin@xxxxxxxxxx>
---
  drivers/watchdog/s3c2410_wdt.c | 32 +++++++++++++++++++++++++++-----
  1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
index 08b8c57dd812..ed561deeeed9 100644
--- a/drivers/watchdog/s3c2410_wdt.c
+++ b/drivers/watchdog/s3c2410_wdt.c
@@ -34,9 +34,10 @@

  #define S3C2410_WTCNT_MAXCNT   0xffff

-#define S3C2410_WTCON_RSTEN    (1 << 0)
-#define S3C2410_WTCON_INTEN    (1 << 2)
-#define S3C2410_WTCON_ENABLE   (1 << 5)
+#define S3C2410_WTCON_RSTEN            (1 << 0)
+#define S3C2410_WTCON_INTEN            (1 << 2)
+#define S3C2410_WTCON_ENABLE           (1 << 5)
+#define S3C2410_WTCON_DBGACK_MASK      (1 << 16)

  #define S3C2410_WTCON_DIV16    (0 << 3)
  #define S3C2410_WTCON_DIV32    (1 << 3)
@@ -107,12 +108,16 @@
   * %QUIRK_HAS_PMU_CNT_EN: PMU block has some register (e.g. CLUSTERx_NONCPU_OUT)
   * with "watchdog counter enable" bit. That bit should be set to make watchdog
   * counter running.
+ *
+ * %QUIRK_HAS_DBGACK_BIT: WTCON register has DBGACK_MASK bit. Enables masking
+ * WDT interrupt and reset request according to CPU core DBGACK signal.
   */
  #define QUIRK_HAS_WTCLRINT_REG                 (1 << 0)
  #define QUIRK_HAS_PMU_MASK_RESET               (1 << 1)
  #define QUIRK_HAS_PMU_RST_STAT                 (1 << 2)
  #define QUIRK_HAS_PMU_AUTO_DISABLE             (1 << 3)
  #define QUIRK_HAS_PMU_CNT_EN                   (1 << 4)
+#define QUIRK_HAS_DBGACK_BIT                   (1 << 5)

  /* These quirks require that we have a PMU register map */
  #define QUIRKS_HAVE_PMUREG \
@@ -279,7 +284,7 @@ static const struct s3c2410_wdt_variant drv_data_gs101_cl0 = {
         .cnt_en_reg = GS_CLUSTER0_NONCPU_OUT,
         .cnt_en_bit = 8,
         .quirks = QUIRK_HAS_PMU_RST_STAT | QUIRK_HAS_PMU_MASK_RESET | QUIRK_HAS_PMU_CNT_EN |
-                 QUIRK_HAS_WTCLRINT_REG,
+                 QUIRK_HAS_WTCLRINT_REG | QUIRK_HAS_DBGACK_BIT,
  };

  static const struct s3c2410_wdt_variant drv_data_gs101_cl1 = {
@@ -291,7 +296,7 @@ static const struct s3c2410_wdt_variant drv_data_gs101_cl1 = {
         .cnt_en_reg = GS_CLUSTER1_NONCPU_OUT,
         .cnt_en_bit = 7,
         .quirks = QUIRK_HAS_PMU_RST_STAT | QUIRK_HAS_PMU_MASK_RESET | QUIRK_HAS_PMU_CNT_EN |
-                 QUIRK_HAS_WTCLRINT_REG,
+                 QUIRK_HAS_WTCLRINT_REG | QUIRK_HAS_DBGACK_BIT,
  };


This patch states it's adding the feature, but in fact it's also
enabling this feature for gs101. Suggest moving this patch before the
one enabling gs101 wdt. This way, one patch will only add the feature,
and another patch will enable gs101 entirely (with this feature used).
At least it seems like more atomic approach to me.


Both approaches have their merits and their downsides. I for my part am not
even sure if DBGACK_MASK should be enabled unconditionally if supported.
With your approach, it would be impossible (or at least more difficult) to
revert if it turns out to be broken and/or have unexpected side effects.
That seems less desirable to me than the current approach.

Guenter





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