* [PATCH] rtc: spacemit: handle regmap_test_bits() error return
@ 2026-07-24 2:42 kr494167
2026-07-24 13:32 ` Alex Elder
0 siblings, 1 reply; 3+ messages in thread
From: kr494167 @ 2026-07-24 2:42 UTC (permalink / raw)
To: alexandre.belloni, dlan
Cc: elder, linux-rtc, linux-riscv, spacemit, linux-kernel,
Surendra Singh Chouhan
From: Surendra Singh Chouhan <kr494167@gmail.com>
p1_rtc_read_time() called if (!regmap_test_bits(regmap, RTC_CTRL, RTC_EN))
to check if the RTC was enabled.
regmap_test_bits() returns 1 if the bit is set, 0 if not set, and a
negative error code (e.g. -EIO) if reading the control register fails.
Using !regmap_test_bits(...) evaluates a negative error code as boolean
false, causing I2C/regmap read failures to be ignored and incorrectly
proceeding to read time registers from a failing device.
Fix this by capturing the return value of regmap_test_bits() and returning
the error code if negative, or -EINVAL if the RTC is disabled.
Fixes: a6de182daa2b ("rtc: spacemit: support the SpacemiT P1 RTC")
Signed-off-by: Surendra Singh Chouhan <kr494167@gmail.com>
---
drivers/rtc/rtc-spacemit-p1.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/rtc/rtc-spacemit-p1.c b/drivers/rtc/rtc-spacemit-p1.c
index 43ab62494bb4..c1820c920ba3 100644
--- a/drivers/rtc/rtc-spacemit-p1.c
+++ b/drivers/rtc/rtc-spacemit-p1.c
@@ -57,8 +57,9 @@ static int p1_rtc_read_time(struct device *dev, struct rtc_time *t)
u8 time[6];
int ret;
- if (!regmap_test_bits(regmap, RTC_CTRL, RTC_EN))
- return -EINVAL; /* RTC is disabled */
+ ret = regmap_test_bits(regmap, RTC_CTRL, RTC_EN);
+ if (ret <= 0)
+ return ret ? ret : -EINVAL; /* RTC is disabled or error */
ret = regmap_bulk_read(regmap, RTC_TIME, time, sizeof(time));
if (ret)
--
2.55.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] rtc: spacemit: handle regmap_test_bits() error return
2026-07-24 2:42 [PATCH] rtc: spacemit: handle regmap_test_bits() error return kr494167
@ 2026-07-24 13:32 ` Alex Elder
2026-07-24 13:39 ` Alexandre Belloni
0 siblings, 1 reply; 3+ messages in thread
From: Alex Elder @ 2026-07-24 13:32 UTC (permalink / raw)
To: kr494167, alexandre.belloni, dlan
Cc: linux-rtc, linux-riscv, spacemit, linux-kernel
On 7/23/26 9:42 PM, kr494167@gmail.com wrote:
> From: Surendra Singh Chouhan <kr494167@gmail.com>
>
> p1_rtc_read_time() called if (!regmap_test_bits(regmap, RTC_CTRL, RTC_EN))
> to check if the RTC was enabled.
>
> regmap_test_bits() returns 1 if the bit is set, 0 if not set, and a
> negative error code (e.g. -EIO) if reading the control register fails.
> Using !regmap_test_bits(...) evaluates a negative error code as boolean
> false, causing I2C/regmap read failures to be ignored and incorrectly
> proceeding to read time registers from a failing device.
>
> Fix this by capturing the return value of regmap_test_bits() and returning
> the error code if negative, or -EINVAL if the RTC is disabled.
>
> Fixes: a6de182daa2b ("rtc: spacemit: support the SpacemiT P1 RTC")
> Signed-off-by: Surendra Singh Chouhan <kr494167@gmail.com>
This is an I2C-based regmap, so yes, we do need to test
for errors when reading or writing registers.
I think this is a good fix. I have a minor suggestion or
two below but either way:
Reviewed-by: Alex Elder <elder@riscstar.com>
> ---
> drivers/rtc/rtc-spacemit-p1.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/rtc/rtc-spacemit-p1.c b/drivers/rtc/rtc-spacemit-p1.c
> index 43ab62494bb4..c1820c920ba3 100644
> --- a/drivers/rtc/rtc-spacemit-p1.c
> +++ b/drivers/rtc/rtc-spacemit-p1.c
> @@ -57,8 +57,9 @@ static int p1_rtc_read_time(struct device *dev, struct rtc_time *t)
> u8 time[6];
> int ret;
>
> - if (!regmap_test_bits(regmap, RTC_CTRL, RTC_EN))
> - return -EINVAL; /* RTC is disabled */
> + ret = regmap_test_bits(regmap, RTC_CTRL, RTC_EN);
> + if (ret <= 0)
> + return ret ? ret : -EINVAL; /* RTC is disabled or error */
Since regmap_test_bits() can return -EINVAL, I wonder if a
different error code would be better to indicate "disabled".
It can return -EBUSY and -EIO too, as well as anything any
regmap->reg_read() can return. Scanning through the list of
basic error codes I don't have a good suggestion, unfortunately.
Otherwise, perhaps just:
return ret ? : -EINVAL; /* comment if you like */
>
> ret = regmap_bulk_read(regmap, RTC_TIME, time, sizeof(time));
> if (ret)
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] rtc: spacemit: handle regmap_test_bits() error return
2026-07-24 13:32 ` Alex Elder
@ 2026-07-24 13:39 ` Alexandre Belloni
0 siblings, 0 replies; 3+ messages in thread
From: Alexandre Belloni @ 2026-07-24 13:39 UTC (permalink / raw)
To: Alex Elder; +Cc: kr494167, dlan, linux-rtc, linux-riscv, spacemit, linux-kernel
On 24/07/2026 08:32:13-0500, Alex Elder wrote:
> On 7/23/26 9:42 PM, kr494167@gmail.com wrote:
> > From: Surendra Singh Chouhan <kr494167@gmail.com>
> >
> > p1_rtc_read_time() called if (!regmap_test_bits(regmap, RTC_CTRL, RTC_EN))
> > to check if the RTC was enabled.
> >
> > regmap_test_bits() returns 1 if the bit is set, 0 if not set, and a
> > negative error code (e.g. -EIO) if reading the control register fails.
> > Using !regmap_test_bits(...) evaluates a negative error code as boolean
> > false, causing I2C/regmap read failures to be ignored and incorrectly
> > proceeding to read time registers from a failing device.
> >
> > Fix this by capturing the return value of regmap_test_bits() and returning
> > the error code if negative, or -EINVAL if the RTC is disabled.
> >
> > Fixes: a6de182daa2b ("rtc: spacemit: support the SpacemiT P1 RTC")
> > Signed-off-by: Surendra Singh Chouhan <kr494167@gmail.com>
>
> This is an I2C-based regmap, so yes, we do need to test
> for errors when reading or writing registers.
>
> I think this is a good fix. I have a minor suggestion or
> two below but either way:
>
> Reviewed-by: Alex Elder <elder@riscstar.com>
>
> > ---
> > drivers/rtc/rtc-spacemit-p1.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/rtc/rtc-spacemit-p1.c b/drivers/rtc/rtc-spacemit-p1.c
> > index 43ab62494bb4..c1820c920ba3 100644
> > --- a/drivers/rtc/rtc-spacemit-p1.c
> > +++ b/drivers/rtc/rtc-spacemit-p1.c
> > @@ -57,8 +57,9 @@ static int p1_rtc_read_time(struct device *dev, struct rtc_time *t)
> > u8 time[6];
> > int ret;
> > - if (!regmap_test_bits(regmap, RTC_CTRL, RTC_EN))
> > - return -EINVAL; /* RTC is disabled */
> > + ret = regmap_test_bits(regmap, RTC_CTRL, RTC_EN);
> > + if (ret <= 0)
> > + return ret ? ret : -EINVAL; /* RTC is disabled or error */
>
> Since regmap_test_bits() can return -EINVAL, I wonder if a
> different error code would be better to indicate "disabled".
> It can return -EBUSY and -EIO too, as well as anything any
> regmap->reg_read() can return. Scanning through the list of
> basic error codes I don't have a good suggestion, unfortunately.
>
No, EINVAL is standard across all the drivers. I considered changing
this to ETIME or ENODATA but that would break userspace too much.
> Otherwise, perhaps just:
>
> return ret ? : -EINVAL; /* comment if you like */
>
> > ret = regmap_bulk_read(regmap, RTC_TIME, time, sizeof(time));
> > if (ret)
>
--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
^ permalink raw reply [flat|nested] 3+ messages in thread
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2026-07-24 13:32 ` Alex Elder
2026-07-24 13:39 ` Alexandre Belloni
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