[PATCH V2 2/3] platform: generic: allwinner: fix OF process for T-HEAD c9xx pmu

[Inochi Amaoto]

T-HEAD c9xx pmu needs to clear OV bits of MCOUNTEROF in any condition
to avoid unnecessary OF interrupts.

In addition, the S-mode SCOUNTEROF only have OF bit set when the related
bits of MCOUNTERWEN is set, so also configure MCOUNTERWEN to allow kernel
to access valid SCOUNTEROF.

Signed-off-by: Haijiao Liu <haijiao.liu at sophgo.com>
Co-authored-by: Inochi Amaoto <inochiama at outlook.com>
Signed-off-by: Inochi Amaoto <inochiama at outlook.com>
---
 platform/generic/allwinner/sun20i-d1.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/platform/generic/allwinner/sun20i-d1.c b/platform/generic/allwinner/sun20i-d1.c
index 0f0a9f3..f59b1e8 100644
--- a/platform/generic/allwinner/sun20i-d1.c
+++ b/platform/generic/allwinner/sun20i-d1.c
@@ -225,22 +225,23 @@ static int sun20i_d1_fdt_fixup(void *fdt, const struct fdt_match *match)

 static void thead_c9xx_pmu_ctr_enable_irq(uint32_t ctr_idx)
 {
-	unsigned long mip_val;
-
 	if (ctr_idx >= SBI_PMU_HW_CTR_MAX)
 		return;

-	mip_val = csr_read(CSR_MIP);
 	/**
 	 * Clear out the OF bit so that next interrupt can be enabled.
-	 * This should be done only when the corresponding overflow interrupt
-	 * bit is cleared. That indicates that software has already handled the
-	 * previous interrupts or the hardware yet to set an overflow interrupt.
-	 * Otherwise, there will be race conditions where we may clear the bit
-	 * the software is yet to handle the interrupt.
+	 * This should be done before starting interrupt to avoid unexcepted
+	 * overflow interrupt.
 	 */
-	if (!(mip_val & THEAD_C9XX_MIP_MOIP))
-		csr_clear(THEAD_C9XX_CSR_MCOUNTEROF, BIT(ctr_idx));
+	csr_clear(THEAD_C9XX_CSR_MCOUNTEROF, BIT(ctr_idx));
+
+	/**
+	 * This register is described in C9xx document as the control register
+	 * for enabling writes to the superuser state counter. However, if the
+	 * corresponding bit is not set to 1, scounterof will always read as 0
+	 * when the counter register overflows.
+	 */
+	csr_set(THEAD_C9XX_CSR_MCOUNTERWEN, BIT(ctr_idx));

 	/**
 	 * SSCOFPMF uses the OF bit for enabling/disabling the interrupt,
@@ -252,6 +253,10 @@ static void thead_c9xx_pmu_ctr_enable_irq(uint32_t ctr_idx)

 static void thead_c9xx_pmu_ctr_disable_irq(uint32_t ctr_idx)
 {
+	/**
+	 * There is no need to clear the bit of mcounterwen, it will expire
+	 * after setting the csr mcountinhibit.
+	 */
 	csr_clear(THEAD_C9XX_CSR_MCOUNTERINTEN, BIT(ctr_idx));
 }

--
2.41.0