Re: [PATCH] clk: mediatek: Don't check HW status for mt8192/5's imp_iic_wrap clocks

From: AngeloGioacchino Del Regno
Date: Tue Jul 12 2022 - 06:58:24 EST

Il 12/07/22 12:56, Chen-Yu Tsai ha scritto:
On Tue, Jul 12, 2022 at 6:55 PM AngeloGioacchino Del Regno
<angelogioacchino.delregno@xxxxxxxxxxxxx> wrote:

Il 12/07/22 12:44, Chen-Yu Tsai ha scritto:

On Tue, Jul 12, 2022 at 4:57 AM Nícolas F. R. A. Prado
<nfraprado@xxxxxxxxxxxxx> wrote:

The imp_iic_wrap clocks on mt8192/mt8195 require that the i2c_sel parent
clock be enabled before their hardware status can be checked. Since this
wasn't taken into account, reading from the clk_summary debugfs file
would cause the system to completely freeze.

Assuming that this clock is managed only by the kernel, and not by any
firmware, simply drop the is_enabled() optional callback and instead
rely on the enable count for the imp_iic_wrap clocks.

That's the wrong way to go about it.

The I2C clocks already have the CLK_OPS_PARENT_ENABLE flag set. So the
issue is that somewhere in the clk core, a piece of code is not honoring
that flag.

And it seems that's in more than one place.

Uhm, you're right. I gave my Tested-by, but not a Reviewed-by because I
wasn't really convinced about this solution being the best.

Now that I think of it, the solution may be as simple as:


static bool clk_core_is_enabled(struct clk_core *core)
bool ret = false;

* If this clock needs parent enabled, but its parent is
* off, we directly return false for two reasons:
* 1. This clock being enabled would be impossible
* 2. The platform may crash for unclocked access while
* reading the status of this clock (where a .is_enabled
* callback is provided).
if (core->flags & CLK_OPS_PARENT_ENABLE &&
return false;

... etc etc etc ...

Nícolas, did you try this approach?

I have a patch ready, but I got distracted by other stuff today.

Let's just wait for your patch then, seems like being the most sensible option.




Signed-off-by: Nícolas F. R. A. Prado <nfraprado@xxxxxxxxxxxxx>


drivers/clk/mediatek/clk-gate.c | 6 ++++++
drivers/clk/mediatek/clk-gate.h | 1 +
drivers/clk/mediatek/clk-mt8192-imp_iic_wrap.c | 2 +-
drivers/clk/mediatek/clk-mt8195-imp_iic_wrap.c | 2 +-
4 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/mediatek/clk-gate.c b/drivers/clk/mediatek/clk-gate.c
index 421806236228..8e7c719a69b3 100644
--- a/drivers/clk/mediatek/clk-gate.c
+++ b/drivers/clk/mediatek/clk-gate.c
@@ -124,6 +124,12 @@ static void mtk_cg_disable_inv_no_setclr(struct clk_hw *hw)

+const struct clk_ops mtk_clk_gate_ops_setclr_counted = {
+ .enable = mtk_cg_enable,
+ .disable = mtk_cg_disable,
const struct clk_ops mtk_clk_gate_ops_setclr = {
.is_enabled = mtk_cg_bit_is_cleared,
.enable = mtk_cg_enable,
diff --git a/drivers/clk/mediatek/clk-gate.h b/drivers/clk/mediatek/clk-gate.h
index d9897ef53528..b5502b2911f5 100644
--- a/drivers/clk/mediatek/clk-gate.h
+++ b/drivers/clk/mediatek/clk-gate.h
@@ -19,6 +19,7 @@ extern const struct clk_ops mtk_clk_gate_ops_setclr;
extern const struct clk_ops mtk_clk_gate_ops_setclr_inv;
extern const struct clk_ops mtk_clk_gate_ops_no_setclr;
extern const struct clk_ops mtk_clk_gate_ops_no_setclr_inv;
+extern const struct clk_ops mtk_clk_gate_ops_setclr_counted;

struct mtk_gate_regs {
u32 sta_ofs;
diff --git a/drivers/clk/mediatek/clk-mt8192-imp_iic_wrap.c b/drivers/clk/mediatek/clk-mt8192-imp_iic_wrap.c
index 700356ac6a58..900ee601169c 100644
--- a/drivers/clk/mediatek/clk-mt8192-imp_iic_wrap.c
+++ b/drivers/clk/mediatek/clk-mt8192-imp_iic_wrap.c
@@ -20,7 +20,7 @@ static const struct mtk_gate_regs imp_iic_wrap_cg_regs = {

#define GATE_IMP_IIC_WRAP(_id, _name, _parent, _shift) \
GATE_MTK_FLAGS(_id, _name, _parent, &imp_iic_wrap_cg_regs, _shift, \
- &mtk_clk_gate_ops_setclr, CLK_OPS_PARENT_ENABLE)
+ &mtk_clk_gate_ops_setclr_counted, CLK_OPS_PARENT_ENABLE)

static const struct mtk_gate imp_iic_wrap_c_clks[] = {
GATE_IMP_IIC_WRAP(CLK_IMP_IIC_WRAP_C_I2C10, "imp_iic_wrap_c_i2c10", "infra_i2c0", 0),
diff --git a/drivers/clk/mediatek/clk-mt8195-imp_iic_wrap.c b/drivers/clk/mediatek/clk-mt8195-imp_iic_wrap.c
index fbc809d05072..e50a77b844f4 100644
--- a/drivers/clk/mediatek/clk-mt8195-imp_iic_wrap.c
+++ b/drivers/clk/mediatek/clk-mt8195-imp_iic_wrap.c
@@ -18,7 +18,7 @@ static const struct mtk_gate_regs imp_iic_wrap_cg_regs = {

#define GATE_IMP_IIC_WRAP(_id, _name, _parent, _shift) \
GATE_MTK_FLAGS(_id, _name, _parent, &imp_iic_wrap_cg_regs, _shift, \
- &mtk_clk_gate_ops_setclr, CLK_OPS_PARENT_ENABLE)
+ &mtk_clk_gate_ops_setclr_counted, CLK_OPS_PARENT_ENABLE)

static const struct mtk_gate imp_iic_wrap_s_clks[] = {
GATE_IMP_IIC_WRAP(CLK_IMP_IIC_WRAP_S_I2C5, "imp_iic_wrap_s_i2c5", "top_i2c", 0),

AngeloGioacchino Del Regno
Software Engineer

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