| Message ID | 89b793993eaa492af531bd7aa9dff1f871fb4a77.1418762900.git.lsorense@csclub.uwaterloo.ca (mailing list archive) |
|---|---|
| State | New, archived |
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Hi Len, On Wednesday 17 December 2014 02:38 AM, Lennart Sorensen wrote: > Errata i856 for the AM572x (DRA7xx) points out that the 32.768KHz external > crystal is not enabled at power up. Instead the CPU falls back to using > an emulation for the 32KHz clock which is SYSCLK1/610. SYSCLK1 is usually > 20MHz on boards so far (which gives an emulated frequency of 32.786KHz), > but can also be 19.2 or 27MHz which result in much larger drift. > > Since this is used to drive the master counter at 32.768KHz * 375 / > 2 = 6.144MHz, the emulated speed for 20MHz is of by 570ppm, or about 43 > seconds per day, and more than the 500ppm NTP is able to tolerate. > > Checking the CTRL_CORE_BOOTSTRAP register can determine if the CPU > is using the real 32.768KHz crystal or the emulated SYSCLK1/610, and > by known that the real counter frequency can be determined and used. > The real speed is then SYSCLK1 / 610 * 375 / 2 or SYSCLK1 * 75 / 244. Looks good to me. Tested this on DRA7 evm. Tested-by: Lokesh Vutla <lokeshvutla@ti.com> Thanks and regards, Lokesh > > Signed-off-by: Len Sorensen <lsorense@csclub.uwaterloo.ca> > --- > arch/arm/mach-omap2/control.h | 4 ++++ > arch/arm/mach-omap2/timer.c | 36 ++++++++++++++++++++++++++++++++++-- > 2 files changed, 38 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/mach-omap2/control.h b/arch/arm/mach-omap2/control.h > index a3c0133..a80ac2d 100644 > --- a/arch/arm/mach-omap2/control.h > +++ b/arch/arm/mach-omap2/control.h > @@ -286,6 +286,10 @@ > #define OMAP5XXX_CONTROL_STATUS 0x134 > #define OMAP5_DEVICETYPE_MASK (0x7 << 6) > > +/* DRA7XX CONTROL CORE BOOTSTRAP */ > +#define DRA7_CTRL_CORE_BOOTSTRAP 0x6c4 > +#define DRA7_SPEEDSELECT_MASK (0x3 << 8) > + > /* > * REVISIT: This list of registers is not comprehensive - there are more > * that should be added. > diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c > index fb0cb2b..7d45c84 100644 > --- a/arch/arm/mach-omap2/timer.c > +++ b/arch/arm/mach-omap2/timer.c > @@ -54,6 +54,7 @@ > > #include "soc.h" > #include "common.h" > +#include "control.h" > #include "powerdomain.h" > #include "omap-secure.h" > > @@ -496,7 +497,8 @@ static void __init realtime_counter_init(void) > void __iomem *base; > static struct clk *sys_clk; > unsigned long rate; > - unsigned int reg, num, den; > + unsigned int reg; > + unsigned long long num, den; > > base = ioremap(REALTIME_COUNTER_BASE, SZ_32); > if (!base) { > @@ -511,6 +513,35 @@ static void __init realtime_counter_init(void) > } > > rate = clk_get_rate(sys_clk); > + > + if (soc_is_dra7xx()) { > + /* > + * Errata i856 says the 32.768KHz crystal does not start at > + * power on, so the CPU falls back to an emulated 32KHz clock > + * based on sysclk / 610 instead. This causes the master counter > + * frequency to not be 6.144MHz but at sysclk / 610 * 375 / 2 > + * (OR sysclk * 75 / 244) > + * > + * This affects at least the DRA7/AM572x 1.0, 1.1 revisions. > + * Of course any board built without a populated 32.768KHz > + * crystal would also need this fix even if the CPU is fixed > + * later. > + * > + * Either case can be detected by using the two speedselect bits > + * If they are not 0, then the 32.768KHz clock driving the > + * coarse counter that corrects the fine counter every time it > + * ticks is actually rate/610 rather than 32.768KHz and we > + * should compensate to avoid the 570ppm (at 20MHz, much worse > + * at other rates) too fast system time. > + */ > + reg = omap_ctrl_readl(DRA7_CTRL_CORE_BOOTSTRAP); > + if (reg & DRA7_SPEEDSELECT_MASK) { > + num = 75; > + den = 244; > + goto sysclk1_based; > + } > + } > + > /* Numerator/denumerator values refer TRM Realtime Counter section */ > switch (rate) { > case 12000000: > @@ -545,6 +576,7 @@ static void __init realtime_counter_init(void) > break; > } > > +sysclk1_based: > /* Program numerator and denumerator registers */ > reg = readl_relaxed(base + INCREMENTER_NUMERATOR_OFFSET) & > NUMERATOR_DENUMERATOR_MASK; > @@ -556,7 +588,7 @@ static void __init realtime_counter_init(void) > reg |= den; > writel_relaxed(reg, base + INCREMENTER_DENUMERATOR_RELOAD_OFFSET); > > - arch_timer_freq = (rate / den) * num; > + arch_timer_freq = DIV_ROUND_UP_ULL(rate * num, den); > set_cntfreq(); > > iounmap(base); > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 14:06-20141217, Lokesh Vutla wrote: > Hi Len, > On Wednesday 17 December 2014 02:38 AM, Lennart Sorensen wrote: > > Errata i856 for the AM572x (DRA7xx) points out that the 32.768KHz external > > crystal is not enabled at power up. Instead the CPU falls back to using > > an emulation for the 32KHz clock which is SYSCLK1/610. SYSCLK1 is usually > > 20MHz on boards so far (which gives an emulated frequency of 32.786KHz), > > but can also be 19.2 or 27MHz which result in much larger drift. > > > > Since this is used to drive the master counter at 32.768KHz * 375 / > > 2 = 6.144MHz, the emulated speed for 20MHz is of by 570ppm, or about 43 > > seconds per day, and more than the 500ppm NTP is able to tolerate. > > > > Checking the CTRL_CORE_BOOTSTRAP register can determine if the CPU > > is using the real 32.768KHz crystal or the emulated SYSCLK1/610, and > > by known that the real counter frequency can be determined and used. > > The real speed is then SYSCLK1 / 610 * 375 / 2 or SYSCLK1 * 75 / 244. > Looks good to me. > Tested this on DRA7 evm. > > Tested-by: Lokesh Vutla <lokeshvutla@ti.com> > > Thanks and regards, > Lokesh > > > > > Signed-off-by: Len Sorensen <lsorense@csclub.uwaterloo.ca> > > --- > > arch/arm/mach-omap2/control.h | 4 ++++ > > arch/arm/mach-omap2/timer.c | 36 ++++++++++++++++++++++++++++++++++-- > > 2 files changed, 38 insertions(+), 2 deletions(-) > > > > diff --git a/arch/arm/mach-omap2/control.h b/arch/arm/mach-omap2/control.h > > index a3c0133..a80ac2d 100644 > > --- a/arch/arm/mach-omap2/control.h > > +++ b/arch/arm/mach-omap2/control.h > > @@ -286,6 +286,10 @@ > > #define OMAP5XXX_CONTROL_STATUS 0x134 > > #define OMAP5_DEVICETYPE_MASK (0x7 << 6) > > > > +/* DRA7XX CONTROL CORE BOOTSTRAP */ > > +#define DRA7_CTRL_CORE_BOOTSTRAP 0x6c4 > > +#define DRA7_SPEEDSELECT_MASK (0x3 << 8) > > + > > /* > > * REVISIT: This list of registers is not comprehensive - there are more > > * that should be added. > > diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c > > index fb0cb2b..7d45c84 100644 > > --- a/arch/arm/mach-omap2/timer.c > > +++ b/arch/arm/mach-omap2/timer.c > > @@ -54,6 +54,7 @@ > > > > #include "soc.h" > > #include "common.h" > > +#include "control.h" > > #include "powerdomain.h" > > #include "omap-secure.h" > > > > @@ -496,7 +497,8 @@ static void __init realtime_counter_init(void) > > void __iomem *base; > > static struct clk *sys_clk; > > unsigned long rate; > > - unsigned int reg, num, den; > > + unsigned int reg; > > + unsigned long long num, den; > > > > base = ioremap(REALTIME_COUNTER_BASE, SZ_32); > > if (!base) { > > @@ -511,6 +513,35 @@ static void __init realtime_counter_init(void) > > } > > > > rate = clk_get_rate(sys_clk); > > + > > + if (soc_is_dra7xx()) { > > + /* > > + * Errata i856 says the 32.768KHz crystal does not start at > > + * power on, so the CPU falls back to an emulated 32KHz clock > > + * based on sysclk / 610 instead. This causes the master counter > > + * frequency to not be 6.144MHz but at sysclk / 610 * 375 / 2 > > + * (OR sysclk * 75 / 244) > > + * > > + * This affects at least the DRA7/AM572x 1.0, 1.1 revisions. > > + * Of course any board built without a populated 32.768KHz > > + * crystal would also need this fix even if the CPU is fixed > > + * later. > > + * > > + * Either case can be detected by using the two speedselect bits > > + * If they are not 0, then the 32.768KHz clock driving the > > + * coarse counter that corrects the fine counter every time it > > + * ticks is actually rate/610 rather than 32.768KHz and we > > + * should compensate to avoid the 570ppm (at 20MHz, much worse > > + * at other rates) too fast system time. > > + */ > > + reg = omap_ctrl_readl(DRA7_CTRL_CORE_BOOTSTRAP); > > + if (reg & DRA7_SPEEDSELECT_MASK) { > > + num = 75; > > + den = 244; > > + goto sysclk1_based; > > + } > > + } > > + > > /* Numerator/denumerator values refer TRM Realtime Counter section */ > > switch (rate) { > > case 12000000: > > @@ -545,6 +576,7 @@ static void __init realtime_counter_init(void) > > break; > > } > > > > +sysclk1_based: > > /* Program numerator and denumerator registers */ > > reg = readl_relaxed(base + INCREMENTER_NUMERATOR_OFFSET) & > > NUMERATOR_DENUMERATOR_MASK; > > @@ -556,7 +588,7 @@ static void __init realtime_counter_init(void) > > reg |= den; > > writel_relaxed(reg, base + INCREMENTER_DENUMERATOR_RELOAD_OFFSET); > > > > - arch_timer_freq = (rate / den) * num; > > + arch_timer_freq = DIV_ROUND_UP_ULL(rate * num, den); > > set_cntfreq(); > > > > iounmap(base); > > > If tony is ok with the arch_timer_freq change in this patch, I am ok with it as well.
* Nishanth Menon <nm@ti.com> [141217 07:33]: > On 14:06-20141217, Lokesh Vutla wrote: > > Hi Len, > > On Wednesday 17 December 2014 02:38 AM, Lennart Sorensen wrote: > > > Errata i856 for the AM572x (DRA7xx) points out that the 32.768KHz external > > > crystal is not enabled at power up. Instead the CPU falls back to using > > > an emulation for the 32KHz clock which is SYSCLK1/610. SYSCLK1 is usually > > > 20MHz on boards so far (which gives an emulated frequency of 32.786KHz), > > > but can also be 19.2 or 27MHz which result in much larger drift. > > > > > > Since this is used to drive the master counter at 32.768KHz * 375 / > > > 2 = 6.144MHz, the emulated speed for 20MHz is of by 570ppm, or about 43 > > > seconds per day, and more than the 500ppm NTP is able to tolerate. > > > > > > Checking the CTRL_CORE_BOOTSTRAP register can determine if the CPU > > > is using the real 32.768KHz crystal or the emulated SYSCLK1/610, and > > > by known that the real counter frequency can be determined and used. > > > The real speed is then SYSCLK1 / 610 * 375 / 2 or SYSCLK1 * 75 / 244. > > Looks good to me. > > Tested this on DRA7 evm. > > > > Tested-by: Lokesh Vutla <lokeshvutla@ti.com> > > > > Thanks and regards, > > Lokesh > > > > > > > > Signed-off-by: Len Sorensen <lsorense@csclub.uwaterloo.ca> > > > --- > > > arch/arm/mach-omap2/control.h | 4 ++++ > > > arch/arm/mach-omap2/timer.c | 36 ++++++++++++++++++++++++++++++++++-- > > > 2 files changed, 38 insertions(+), 2 deletions(-) > > > > > > diff --git a/arch/arm/mach-omap2/control.h b/arch/arm/mach-omap2/control.h > > > index a3c0133..a80ac2d 100644 > > > --- a/arch/arm/mach-omap2/control.h > > > +++ b/arch/arm/mach-omap2/control.h > > > @@ -286,6 +286,10 @@ > > > #define OMAP5XXX_CONTROL_STATUS 0x134 > > > #define OMAP5_DEVICETYPE_MASK (0x7 << 6) > > > > > > +/* DRA7XX CONTROL CORE BOOTSTRAP */ > > > +#define DRA7_CTRL_CORE_BOOTSTRAP 0x6c4 > > > +#define DRA7_SPEEDSELECT_MASK (0x3 << 8) > > > + > > > /* > > > * REVISIT: This list of registers is not comprehensive - there are more > > > * that should be added. > > > diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c > > > index fb0cb2b..7d45c84 100644 > > > --- a/arch/arm/mach-omap2/timer.c > > > +++ b/arch/arm/mach-omap2/timer.c > > > @@ -54,6 +54,7 @@ > > > > > > #include "soc.h" > > > #include "common.h" > > > +#include "control.h" > > > #include "powerdomain.h" > > > #include "omap-secure.h" > > > > > > @@ -496,7 +497,8 @@ static void __init realtime_counter_init(void) > > > void __iomem *base; > > > static struct clk *sys_clk; > > > unsigned long rate; > > > - unsigned int reg, num, den; > > > + unsigned int reg; > > > + unsigned long long num, den; > > > > > > base = ioremap(REALTIME_COUNTER_BASE, SZ_32); > > > if (!base) { > > > @@ -511,6 +513,35 @@ static void __init realtime_counter_init(void) > > > } > > > > > > rate = clk_get_rate(sys_clk); > > > + > > > + if (soc_is_dra7xx()) { > > > + /* > > > + * Errata i856 says the 32.768KHz crystal does not start at > > > + * power on, so the CPU falls back to an emulated 32KHz clock > > > + * based on sysclk / 610 instead. This causes the master counter > > > + * frequency to not be 6.144MHz but at sysclk / 610 * 375 / 2 > > > + * (OR sysclk * 75 / 244) > > > + * > > > + * This affects at least the DRA7/AM572x 1.0, 1.1 revisions. > > > + * Of course any board built without a populated 32.768KHz > > > + * crystal would also need this fix even if the CPU is fixed > > > + * later. > > > + * > > > + * Either case can be detected by using the two speedselect bits > > > + * If they are not 0, then the 32.768KHz clock driving the > > > + * coarse counter that corrects the fine counter every time it > > > + * ticks is actually rate/610 rather than 32.768KHz and we > > > + * should compensate to avoid the 570ppm (at 20MHz, much worse > > > + * at other rates) too fast system time. > > > + */ > > > + reg = omap_ctrl_readl(DRA7_CTRL_CORE_BOOTSTRAP); > > > + if (reg & DRA7_SPEEDSELECT_MASK) { > > > + num = 75; > > > + den = 244; > > > + goto sysclk1_based; > > > + } > > > + } > > > + > > > /* Numerator/denumerator values refer TRM Realtime Counter section */ > > > switch (rate) { > > > case 12000000: > > > @@ -545,6 +576,7 @@ static void __init realtime_counter_init(void) > > > break; > > > } > > > > > > +sysclk1_based: > > > /* Program numerator and denumerator registers */ > > > reg = readl_relaxed(base + INCREMENTER_NUMERATOR_OFFSET) & > > > NUMERATOR_DENUMERATOR_MASK; > > > @@ -556,7 +588,7 @@ static void __init realtime_counter_init(void) > > > reg |= den; > > > writel_relaxed(reg, base + INCREMENTER_DENUMERATOR_RELOAD_OFFSET); > > > > > > - arch_timer_freq = (rate / den) * num; > > > + arch_timer_freq = DIV_ROUND_UP_ULL(rate * num, den); > > > set_cntfreq(); > > > > > > iounmap(base); > > > > > > If tony is ok with the arch_timer_freq change in this patch, I am ok > with it as well. Looks good to me thanks. Applying both into omap-for-v3.19/fixes with the first cc stable v3.7+ and the second cc stable v3.14+. Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/arm/mach-omap2/control.h b/arch/arm/mach-omap2/control.h index a3c0133..a80ac2d 100644 --- a/arch/arm/mach-omap2/control.h +++ b/arch/arm/mach-omap2/control.h @@ -286,6 +286,10 @@ #define OMAP5XXX_CONTROL_STATUS 0x134 #define OMAP5_DEVICETYPE_MASK (0x7 << 6) +/* DRA7XX CONTROL CORE BOOTSTRAP */ +#define DRA7_CTRL_CORE_BOOTSTRAP 0x6c4 +#define DRA7_SPEEDSELECT_MASK (0x3 << 8) + /* * REVISIT: This list of registers is not comprehensive - there are more * that should be added. diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c index fb0cb2b..7d45c84 100644 --- a/arch/arm/mach-omap2/timer.c +++ b/arch/arm/mach-omap2/timer.c @@ -54,6 +54,7 @@ #include "soc.h" #include "common.h" +#include "control.h" #include "powerdomain.h" #include "omap-secure.h" @@ -496,7 +497,8 @@ static void __init realtime_counter_init(void) void __iomem *base; static struct clk *sys_clk; unsigned long rate; - unsigned int reg, num, den; + unsigned int reg; + unsigned long long num, den; base = ioremap(REALTIME_COUNTER_BASE, SZ_32); if (!base) { @@ -511,6 +513,35 @@ static void __init realtime_counter_init(void) } rate = clk_get_rate(sys_clk); + + if (soc_is_dra7xx()) { + /* + * Errata i856 says the 32.768KHz crystal does not start at + * power on, so the CPU falls back to an emulated 32KHz clock + * based on sysclk / 610 instead. This causes the master counter + * frequency to not be 6.144MHz but at sysclk / 610 * 375 / 2 + * (OR sysclk * 75 / 244) + * + * This affects at least the DRA7/AM572x 1.0, 1.1 revisions. + * Of course any board built without a populated 32.768KHz + * crystal would also need this fix even if the CPU is fixed + * later. + * + * Either case can be detected by using the two speedselect bits + * If they are not 0, then the 32.768KHz clock driving the + * coarse counter that corrects the fine counter every time it + * ticks is actually rate/610 rather than 32.768KHz and we + * should compensate to avoid the 570ppm (at 20MHz, much worse + * at other rates) too fast system time. + */ + reg = omap_ctrl_readl(DRA7_CTRL_CORE_BOOTSTRAP); + if (reg & DRA7_SPEEDSELECT_MASK) { + num = 75; + den = 244; + goto sysclk1_based; + } + } + /* Numerator/denumerator values refer TRM Realtime Counter section */ switch (rate) { case 12000000: @@ -545,6 +576,7 @@ static void __init realtime_counter_init(void) break; } +sysclk1_based: /* Program numerator and denumerator registers */ reg = readl_relaxed(base + INCREMENTER_NUMERATOR_OFFSET) & NUMERATOR_DENUMERATOR_MASK; @@ -556,7 +588,7 @@ static void __init realtime_counter_init(void) reg |= den; writel_relaxed(reg, base + INCREMENTER_DENUMERATOR_RELOAD_OFFSET); - arch_timer_freq = (rate / den) * num; + arch_timer_freq = DIV_ROUND_UP_ULL(rate * num, den); set_cntfreq(); iounmap(base);
Errata i856 for the AM572x (DRA7xx) points out that the 32.768KHz external crystal is not enabled at power up. Instead the CPU falls back to using an emulation for the 32KHz clock which is SYSCLK1/610. SYSCLK1 is usually 20MHz on boards so far (which gives an emulated frequency of 32.786KHz), but can also be 19.2 or 27MHz which result in much larger drift. Since this is used to drive the master counter at 32.768KHz * 375 / 2 = 6.144MHz, the emulated speed for 20MHz is of by 570ppm, or about 43 seconds per day, and more than the 500ppm NTP is able to tolerate. Checking the CTRL_CORE_BOOTSTRAP register can determine if the CPU is using the real 32.768KHz crystal or the emulated SYSCLK1/610, and by known that the real counter frequency can be determined and used. The real speed is then SYSCLK1 / 610 * 375 / 2 or SYSCLK1 * 75 / 244. Signed-off-by: Len Sorensen <lsorense@csclub.uwaterloo.ca> --- arch/arm/mach-omap2/control.h | 4 ++++ arch/arm/mach-omap2/timer.c | 36 ++++++++++++++++++++++++++++++++++-- 2 files changed, 38 insertions(+), 2 deletions(-)