* [PATCH] iio: adc: max9611: Defer probe on POR read @ 2019-10-16 10:25 Jacopo Mondi 2019-10-17 12:55 ` Geert Uytterhoeven 0 siblings, 1 reply; 5+ messages in thread From: Jacopo Mondi @ 2019-10-16 10:25 UTC (permalink / raw) To: geert+renesas; +Cc: Jacopo Mondi, linux-iio, linux-renesas-soc, linux-kernel The max9611 driver tests communications with the chip by reading the die temperature during the probe function. If the temperature register POR (power-on reset) value is returned from the test read, defer probe to give the chip a bit more time to properly exit from reset. Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org> --- Geert, I've not been able to reproduce the issue on my boards (M3-N Salvator-XS and M3-W Salvator-X). As you reported the issue you might be able to reproduce it, could you please test this? Also, I opted for deferring probe instead of arbitrary repeat the temperature read. What's your opinion? Thanks j --- drivers/iio/adc/max9611.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/iio/adc/max9611.c b/drivers/iio/adc/max9611.c index da073d72f649..30ae5879252c 100644 --- a/drivers/iio/adc/max9611.c +++ b/drivers/iio/adc/max9611.c @@ -80,6 +80,7 @@ * The complete formula to calculate temperature is: * ((adc_read >> 7) * 1000) / (1 / 480 * 1000) */ +#define MAX9611_TEMP_POR 0x8000 #define MAX9611_TEMP_MAX_POS 0x7f80 #define MAX9611_TEMP_MAX_NEG 0xff80 #define MAX9611_TEMP_MIN_NEG 0xd980 @@ -480,8 +481,10 @@ static int max9611_init(struct max9611_dev *max9611) if (ret) return ret; - regval &= MAX9611_TEMP_MASK; + if (regval == MAX9611_TEMP_POR) + return -EPROBE_DEFER; + regval &= MAX9611_TEMP_MASK; if ((regval > MAX9611_TEMP_MAX_POS && regval < MAX9611_TEMP_MIN_NEG) || regval > MAX9611_TEMP_MAX_NEG) { -- 2.23.0 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] iio: adc: max9611: Defer probe on POR read 2019-10-16 10:25 [PATCH] iio: adc: max9611: Defer probe on POR read Jacopo Mondi @ 2019-10-17 12:55 ` Geert Uytterhoeven 2019-11-10 17:15 ` Jonathan Cameron 2019-11-10 18:45 ` Geert Uytterhoeven 0 siblings, 2 replies; 5+ messages in thread From: Geert Uytterhoeven @ 2019-10-17 12:55 UTC (permalink / raw) To: Jacopo Mondi Cc: linux-iio, Linux-Renesas, Linux Kernel Mailing List, Wolfram Sang, Linux I2C Hi Jacopo, CC i2c On Wed, Oct 16, 2019 at 12:23 PM Jacopo Mondi <jacopo+renesas@jmondi.org> wrote: > The max9611 driver tests communications with the chip by reading the die > temperature during the probe function. If the temperature register > POR (power-on reset) value is returned from the test read, defer probe to > give the chip a bit more time to properly exit from reset. > > Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> > Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org> Thanks for your patch! > Geert, > I've not been able to reproduce the issue on my boards (M3-N > Salvator-XS and M3-W Salvator-X). As you reported the issue you might be > able to reproduce it, could you please test this? I can reproduce it on Salvator-XS with R-Car H3 ES2.0. According to my logs, I've seen the issue on all Salvator-X(S) boards, but not with the same frequency. Probability is highest on H3 ES2.0 (ca. 5% of the boots since I first saw the issue), followed by H3 ES1.0, M3-W, and M3-N. After more investigation, my findings are: 1. I cannot reproduce the issue if the max9611 driver is modular. Is it related to using max9611 "too soon" after i2c bus init? How can "i2c bus init" impact a slave device? Perhaps due to pin configuration, e.g. changing from another pin function or GPIO to function i2c4? 2. Adding a delay at the top of max9611_init() fixes the issue. This would explain why the issue is less likely to happy on slower SoCs like M3-N. 3. Disabling all other i2c slaves on i2c4 in DTS fixes the issue. Before, max9611 was initialized last, so this moves init earlier, contradicting theory #1. 4. Just disabling the adv7482 (which registers 11 dummies i2c slaves) in DTS does not fix the issue. Unfortunately i2c4 is exposed on a 60-pin Samtec QSH connector only, for which I have no breakout adapter. Wolfram: do you have any clues? > Also, I opted for deferring probe instead of arbitrary repeat the > temperature read. What's your opinion? While this is probably OK if the max9611 driver is built-in, I'm afraid this may lead to unbounded delays for a reprobe in case the driver is modular. > --- a/drivers/iio/adc/max9611.c > +++ b/drivers/iio/adc/max9611.c > @@ -80,6 +80,7 @@ > * The complete formula to calculate temperature is: > * ((adc_read >> 7) * 1000) / (1 / 480 * 1000) > */ > +#define MAX9611_TEMP_POR 0x8000 > #define MAX9611_TEMP_MAX_POS 0x7f80 > #define MAX9611_TEMP_MAX_NEG 0xff80 > #define MAX9611_TEMP_MIN_NEG 0xd980 > @@ -480,8 +481,10 @@ static int max9611_init(struct max9611_dev *max9611) > if (ret) > return ret; > > - regval &= MAX9611_TEMP_MASK; > + if (regval == MAX9611_TEMP_POR) > + return -EPROBE_DEFER; > > + regval &= MAX9611_TEMP_MASK; > if ((regval > MAX9611_TEMP_MAX_POS && > regval < MAX9611_TEMP_MIN_NEG) || > regval > MAX9611_TEMP_MAX_NEG) { Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] iio: adc: max9611: Defer probe on POR read 2019-10-17 12:55 ` Geert Uytterhoeven @ 2019-11-10 17:15 ` Jonathan Cameron 2019-11-10 18:45 ` Geert Uytterhoeven 1 sibling, 0 replies; 5+ messages in thread From: Jonathan Cameron @ 2019-11-10 17:15 UTC (permalink / raw) To: Geert Uytterhoeven Cc: Jacopo Mondi, linux-iio, Linux-Renesas, Linux Kernel Mailing List, Wolfram Sang, Linux I2C On Thu, 17 Oct 2019 14:55:58 +0200 Geert Uytterhoeven <geert@linux-m68k.org> wrote: > Hi Jacopo, > > CC i2c Ping. Wolfram, a query in here for you. Thanks, Jonathan > > On Wed, Oct 16, 2019 at 12:23 PM Jacopo Mondi <jacopo+renesas@jmondi.org> wrote: > > The max9611 driver tests communications with the chip by reading the die > > temperature during the probe function. If the temperature register > > POR (power-on reset) value is returned from the test read, defer probe to > > give the chip a bit more time to properly exit from reset. > > > > Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> > > Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org> > > Thanks for your patch! > > > Geert, > > I've not been able to reproduce the issue on my boards (M3-N > > Salvator-XS and M3-W Salvator-X). As you reported the issue you might be > > able to reproduce it, could you please test this? > > I can reproduce it on Salvator-XS with R-Car H3 ES2.0. > According to my logs, I've seen the issue on all Salvator-X(S) boards, > but not with the same frequency. Probability is highest on H3 ES2.0 > (ca. 5% of the boots since I first saw the issue), followed by H3 ES1.0, > M3-W, and M3-N. > > After more investigation, my findings are: > 1. I cannot reproduce the issue if the max9611 driver is modular. > Is it related to using max9611 "too soon" after i2c bus init? > How can "i2c bus init" impact a slave device? > Perhaps due to pin configuration, e.g. changing from another pin > function or GPIO to function i2c4? > 2. Adding a delay at the top of max9611_init() fixes the issue. > This would explain why the issue is less likely to happy on slower > SoCs like M3-N. > 3. Disabling all other i2c slaves on i2c4 in DTS fixes the issue. > Before, max9611 was initialized last, so this moves init earlier, > contradicting theory #1. > 4. Just disabling the adv7482 (which registers 11 dummies i2c slaves) > in DTS does not fix the issue. > > Unfortunately i2c4 is exposed on a 60-pin Samtec QSH connector only, > for which I have no breakout adapter. > > Wolfram: do you have any clues? > > > Also, I opted for deferring probe instead of arbitrary repeat the > > temperature read. What's your opinion? > > While this is probably OK if the max9611 driver is built-in, I'm afraid > this may lead to unbounded delays for a reprobe in case the driver > is modular. > > > --- a/drivers/iio/adc/max9611.c > > +++ b/drivers/iio/adc/max9611.c > > @@ -80,6 +80,7 @@ > > * The complete formula to calculate temperature is: > > * ((adc_read >> 7) * 1000) / (1 / 480 * 1000) > > */ > > +#define MAX9611_TEMP_POR 0x8000 > > #define MAX9611_TEMP_MAX_POS 0x7f80 > > #define MAX9611_TEMP_MAX_NEG 0xff80 > > #define MAX9611_TEMP_MIN_NEG 0xd980 > > @@ -480,8 +481,10 @@ static int max9611_init(struct max9611_dev *max9611) > > if (ret) > > return ret; > > > > - regval &= MAX9611_TEMP_MASK; > > + if (regval == MAX9611_TEMP_POR) > > + return -EPROBE_DEFER; > > > > + regval &= MAX9611_TEMP_MASK; > > if ((regval > MAX9611_TEMP_MAX_POS && > > regval < MAX9611_TEMP_MIN_NEG) || > > regval > MAX9611_TEMP_MAX_NEG) { > > Gr{oetje,eeting}s, > > Geert > ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] iio: adc: max9611: Defer probe on POR read 2019-10-17 12:55 ` Geert Uytterhoeven 2019-11-10 17:15 ` Jonathan Cameron @ 2019-11-10 18:45 ` Geert Uytterhoeven 2019-11-13 9:41 ` Geert Uytterhoeven 1 sibling, 1 reply; 5+ messages in thread From: Geert Uytterhoeven @ 2019-11-10 18:45 UTC (permalink / raw) To: Jacopo Mondi Cc: linux-iio, Linux-Renesas, Linux Kernel Mailing List, Wolfram Sang, Linux I2C On Thu, Oct 17, 2019 at 2:55 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote: > On Wed, Oct 16, 2019 at 12:23 PM Jacopo Mondi <jacopo+renesas@jmondi.org> wrote: > > The max9611 driver tests communications with the chip by reading the die > > temperature during the probe function. If the temperature register > > POR (power-on reset) value is returned from the test read, defer probe to > > give the chip a bit more time to properly exit from reset. > > > > Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> > > Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org> > > Thanks for your patch! > > > Geert, > > I've not been able to reproduce the issue on my boards (M3-N > > Salvator-XS and M3-W Salvator-X). As you reported the issue you might be > > able to reproduce it, could you please test this? > > I can reproduce it on Salvator-XS with R-Car H3 ES2.0. > According to my logs, I've seen the issue on all Salvator-X(S) boards, > but not with the same frequency. Probability is highest on H3 ES2.0 > (ca. 5% of the boots since I first saw the issue), followed by H3 ES1.0, > M3-W, and M3-N. > > After more investigation, my findings are: > 1. I cannot reproduce the issue if the max9611 driver is modular. > Is it related to using max9611 "too soon" after i2c bus init? > How can "i2c bus init" impact a slave device? > Perhaps due to pin configuration, e.g. changing from another pin > function or GPIO to function i2c4? > 2. Adding a delay at the top of max9611_init() fixes the issue. > This would explain why the issue is less likely to happy on slower > SoCs like M3-N. > 3. Disabling all other i2c slaves on i2c4 in DTS fixes the issue. > Before, max9611 was initialized last, so this moves init earlier, > contradicting theory #1. > 4. Just disabling the adv7482 (which registers 11 dummies i2c slaves) > in DTS does not fix the issue. > > Unfortunately i2c4 is exposed on a 60-pin Samtec QSH connector only, > for which I have no breakout adapter. Some soldering fixed that. Still investigating. Here's a status update: A. I can reproduce the issue at 100 kHz instead of 400 kHz. B. 3 above doesn't seem to be true: I can reproduce it with all other slaves disabled. C. The code says: /* * need a delay here to make register configuration * stabilize. 1 msec at least, from empirical testing. */ usleep_range(1000, 2000); However, the datasheet says: Parameter MIN TYP MAX Conversion Time - 2 ms - So 1 ms is definitely too short. Unfortunately the datasheet has no maximum value. D. For 2: msleep(1) is sufficient, usleep_range(200, 500) is not. And this is still not explained by C. I also don't know yet who's resetting the chip on reboot, as it does not have a reset line, but all registers are zeroed (except for the POR temperature value). To be investigated more... Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] iio: adc: max9611: Defer probe on POR read 2019-11-10 18:45 ` Geert Uytterhoeven @ 2019-11-13 9:41 ` Geert Uytterhoeven 0 siblings, 0 replies; 5+ messages in thread From: Geert Uytterhoeven @ 2019-11-13 9:41 UTC (permalink / raw) To: Jacopo Mondi Cc: linux-iio, Linux-Renesas, Linux Kernel Mailing List, Wolfram Sang, Linux I2C On Sun, Nov 10, 2019 at 7:45 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote: > On Thu, Oct 17, 2019 at 2:55 PM Geert Uytterhoeven <geert@linux-m68k.org> wrote: > > On Wed, Oct 16, 2019 at 12:23 PM Jacopo Mondi <jacopo+renesas@jmondi.org> wrote: > > > The max9611 driver tests communications with the chip by reading the die > > > temperature during the probe function. If the temperature register > > > POR (power-on reset) value is returned from the test read, defer probe to > > > give the chip a bit more time to properly exit from reset. > > > > > > Reported-by: Geert Uytterhoeven <geert+renesas@glider.be> > > > Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org> > > > > > I've not been able to reproduce the issue on my boards (M3-N > > > Salvator-XS and M3-W Salvator-X). As you reported the issue you might be > > > able to reproduce it, could you please test this? > > > > I can reproduce it on Salvator-XS with R-Car H3 ES2.0. > > According to my logs, I've seen the issue on all Salvator-X(S) boards, > > but not with the same frequency. Probability is highest on H3 ES2.0 > > (ca. 5% of the boots since I first saw the issue), followed by H3 ES1.0, > > M3-W, and M3-N. > > > > After more investigation, my findings are: > > 1. I cannot reproduce the issue if the max9611 driver is modular. > > Is it related to using max9611 "too soon" after i2c bus init? > > How can "i2c bus init" impact a slave device? > > Perhaps due to pin configuration, e.g. changing from another pin > > function or GPIO to function i2c4? Not true: I managed to reproduce it with a modular driver. > > 2. Adding a delay at the top of max9611_init() fixes the issue. > > This would explain why the issue is less likely to happy on slower > > SoCs like M3-N. > > 3. Disabling all other i2c slaves on i2c4 in DTS fixes the issue. > > Before, max9611 was initialized last, so this moves init earlier, > > contradicting theory #1. > > 4. Just disabling the adv7482 (which registers 11 dummies i2c slaves) > > in DTS does not fix the issue. > > > > Unfortunately i2c4 is exposed on a 60-pin Samtec QSH connector only, > > for which I have no breakout adapter. > > Some soldering fixed that. Still investigating. > Here's a status update: > > A. I can reproduce the issue at 100 kHz instead of 400 kHz. > B. 3 above doesn't seem to be true: I can reproduce it with all other > slaves disabled. > C. The code says: > > /* > * need a delay here to make register configuration > * stabilize. 1 msec at least, from empirical testing. > */ > usleep_range(1000, 2000); > > However, the datasheet says: > > Parameter MIN TYP MAX > Conversion Time - 2 ms - > > So 1 ms is definitely too short. > Unfortunately the datasheet has no maximum value. usleep_range(1000, 2000) usually results in a sleep time of 2.0 ms: OK It may take longer: I saw 4.8 -- 7.7 ms (nothing in between 2.0 -- 4.8!): OK It may take shorter: - 1.2 -- 1.7 ms: FAIL - 1.8 ms - 2 ms: OK So a minimum delay of 2 ms seems like a good value. > D. For 2: msleep(1) is sufficient, usleep_range(200, 500) is not. > And this is still not explained by C. Without adding an msleep() call to max9611_init(), the usleep_range() call in max9611_read_single() happens at an arbitrary moment. After adding an msleep() call to max9611_init(), the code becomes synchronized to the jiffies clock, and the usleep_range() call in max9611_read_single() never completes in less than 2 ms, thus avoiding the issue. > I also don't know yet who's resetting the chip on reboot, as it > does not have a reset line, but all registers are zeroed (except > for the POR temperature value). Looks like the PMIC powers down the +3.3V rail for ca. 25 ms when PSCI initiates a system reboot. Patch sent: "[PATCH] iio: adc: max9611: Fix too short conversion time delay" (https://lore.kernel.org/lkml/20191113092133.23723-1-geert+renesas@glider.be/). Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2019-11-13 9:41 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2019-10-16 10:25 [PATCH] iio: adc: max9611: Defer probe on POR read Jacopo Mondi 2019-10-17 12:55 ` Geert Uytterhoeven 2019-11-10 17:15 ` Jonathan Cameron 2019-11-10 18:45 ` Geert Uytterhoeven 2019-11-13 9:41 ` Geert Uytterhoeven
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