[ +Govindraj for omap-serial ]
Nishanth Menon <nm@xxxxxx> writes:
> From: Archana Sriram <archana.sriram@xxxxxx>
>
> Errata Id:i582
>
> PER Domain reset issue after Domain-OFF/OSWR Wakeup.
>
> Issue:
> When Peripheral Power Domain (PER-PD) is woken up from OFF / OSWR
> state while Core Power Domain (CORE-PD) is kept active, write or
> read access to some internal memory (e.g., UART3 FIFO) does not
> work correctly.
>
> Workaround :
> * Prevent PER from going off when CORE has not gone to off.
We currently prevent this from happening in CPUidle: omap3_enter_idle_bm.
Its not clear if this patch is trying to do something additional
> * When both CORE-PD and PER-PD goes into OSWR/OFF, PER-PD should be
> brought to active before CORE-PD.This can be done by configuring a wakeup
> dependency so that CORE-PD and PER-PD will wake up at the same time.
>
> Acked-by: Tero Kristo <tero.kristo@xxxxxxxxx>
> Tested-by: Eduardo Valentin <eduardo.valentin@xxxxxxxxx>
> Tested-by: Westerberg Mika <ext-mika.1.westerberg@xxxxxxxxx>
>
> [vishwanath.bs@xxxxxx: initial code and suggestions]
> Signed-off-by: Vishwanath BS <vishwanath.bs@xxxxxx>
> [nm@xxxxxx: forward ported to 2.6.37-rc2 and suggestions]
> Signed-off-by: Nishanth Menon <nm@xxxxxx>
> Signed-off-by: Archana Sriram <archana.sriram@xxxxxx>
I don't think the workaround for this erratum belongs in the PM core.
Rather, it seems to me that it belongs in the UART core, or even better,
the omap-serial driver (once it grows runtime PM support, which should
happen real soon now.)
We would like to to keep device specific idle/errata management in
device specific code wherever possible. This seems like an example
where this will be straight forward.
> ---
> arch/arm/mach-omap2/pm34xx.c | 41 +++++++++++++++-
> arch/arm/mach-omap2/serial.c | 80 ++++++++++++++++++++++++++++++
> arch/arm/plat-omap/include/plat/serial.h | 4 ++
> 3 files changed, 124 insertions(+), 1 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/pm34xx.c b/arch/arm/mach-omap2/pm34xx.c
> index c7e2db0..218d0b0 100644
> --- a/arch/arm/mach-omap2/pm34xx.c
> +++ b/arch/arm/mach-omap2/pm34xx.c
> @@ -84,6 +84,10 @@ static struct powerdomain *cam_pwrdm;
> static int secure_ram_save_status;
> static int secure_ram_saved;
>
> +#define PER_WAKEUP_ERRATA_i582 (1 << 0)
> +static u16 pm34xx_errata;
> +#define IS_PM34XX_ERRATA(id) (pm34xx_errata & (id))
> +
> static inline void omap3_per_save_context(void)
> {
> omap_gpio_save_context();
> @@ -371,7 +375,8 @@ void omap_sram_idle(void)
> int mpu_next_state = PWRDM_POWER_ON;
> int per_next_state = PWRDM_POWER_ON;
> int core_next_state = PWRDM_POWER_ON;
> - int core_prev_state, per_prev_state;
> + int core_prev_state = PWRDM_POWER_ON;
> + int per_prev_state = PWRDM_POWER_ON;
> u32 sdrc_pwr = 0;
>
> if (!_omap_sram_idle)
> @@ -496,6 +501,23 @@ void omap_sram_idle(void)
> omap3_per_restore_context();
> omap_uart_resume_idle(2);
> omap_uart_resume_idle(3);
> + if (IS_PM34XX_ERRATA(PER_WAKEUP_ERRATA_i582) &&
> + omap_uart_check_per_uarts_used() &&
> + (core_prev_state == PWRDM_POWER_ON) &&
> + (per_prev_state == PWRDM_POWER_OFF)) {
If the condition above is prevented, how is this happening?
As stated above, why can't this checking be done inside the UART core
(in this case omap_uart_resume_idle() ?)
> + /*
> + * We dont seem to have a real recovery other than reset
> + * Errata i582:Alternative available here is to do a
> + * reboot OR go to per off/core off, we will just print
> + * and cause uart to be in an unstable state and
> + * continue on till we hit the next off transition.
> + * Reboot of the device due to this corner case is
> + * undesirable.
> + */
> + if (omap_uart_per_errata())
> + pr_err("%s: PER UART hit with Errata i582 "
> + "Corner case.\n", __func__);
> + }
> }
>
> /* Disable IO-PAD and IO-CHAIN wakeup */
> @@ -1021,15 +1043,27 @@ void omap_push_sram_idle(void)
> save_secure_ram_context_sz);
> }
>
> +static void pm_errata_configure(void)
> +{
> + if (cpu_is_omap34xx()) {
> + pm34xx_errata |= PER_WAKEUP_ERRATA_i582;
> + if (cpu_is_omap3630() && (omap_rev() > OMAP3630_REV_ES1_1))
> + pm34xx_errata &= ~PER_WAKEUP_ERRATA_i582;
> + }
> +}
> +
> static int __init omap3_pm_init(void)
> {
> struct power_state *pwrst, *tmp;
> struct clockdomain *neon_clkdm, *per_clkdm, *mpu_clkdm, *core_clkdm;
> + struct clockdomain *wkup_clkdm;
> int ret;
>
> if (!cpu_is_omap34xx())
> return -ENODEV;
>
> + pm_errata_configure();
> +
> printk(KERN_ERR "Power Management for TI OMAP3.\n");
>
> /* XXX prcm_setup_regs needs to be before enabling hw
> @@ -1067,6 +1101,7 @@ static int __init omap3_pm_init(void)
> neon_clkdm = clkdm_lookup("neon_clkdm");
> mpu_clkdm = clkdm_lookup("mpu_clkdm");
> per_clkdm = clkdm_lookup("per_clkdm");
> + wkup_clkdm = clkdm_lookup("wkup_clkdm");
this isn't used in this patch
> core_clkdm = clkdm_lookup("core_clkdm");
>
> omap_push_sram_idle();
> @@ -1077,6 +1112,10 @@ static int __init omap3_pm_init(void)
> pm_idle = omap3_pm_idle;
> omap3_idle_init();
>
> + /* Allow per to wakeup the system if errata is applicable */
This comment isn't accurate with what the code is doing. Adding a
wakedep does not necessarily allow per to wakeup the system.
> + if (IS_PM34XX_ERRATA(PER_WAKEUP_ERRATA_i582) && cpu_is_omap34xx())
> + clkdm_add_wkdep(per_clkdm, wkup_clkdm);
> +
> clkdm_add_wkdep(neon_clkdm, mpu_clkdm);
>
> omap3_save_scratchpad_contents();
> diff --git a/arch/arm/mach-omap2/serial.c b/arch/arm/mach-omap2/serial.c
> index becf0e3..43c2ec4 100644
> --- a/arch/arm/mach-omap2/serial.c
> +++ b/arch/arm/mach-omap2/serial.c
> @@ -273,6 +273,86 @@ static void omap_uart_restore_context(struct omap_uart_state *uart)
> /* UART 16x mode */
> serial_write_reg(uart, UART_OMAP_MDR1, 0x00);
> }
> +
> +static inline int _is_per_uart(struct omap_uart_state *uart)
> +{
> + if (cpu_is_omap34xx() && (uart->num == 2 || uart->num == 3))
> + return 1;
> + return 0;
> +}
> +
> +int omap_uart_check_per_uarts_used(void)
> +{
> + struct omap_uart_state *uart;
> +
> + list_for_each_entry(uart, &uart_list, node) {
> + if (_is_per_uart(uart))
> + return 1;
> + }
> + return 0;
> +}
> +
> +/*
> + * Errata i582 affects PER UARTS..Loop back test is done to
> + * check the UART state when the corner case is encountered
> + */
> +static int omap_uart_loopback_test(struct omap_uart_state *uart)
> +{
> + u8 loopbk_rhr = 0;
> +
> + omap_uart_save_context(uart);
> + serial_write_reg(uart, UART_OMAP_MDR1, 0x7);
> + serial_write_reg(uart, UART_LCR, 0xBF); /* Config B mode */
> + serial_write_reg(uart, UART_DLL, uart->dll);
> + serial_write_reg(uart, UART_DLM, uart->dlh);
> + serial_write_reg(uart, UART_LCR, 0x0); /* Operational mode */
> + /* configure uart3 in UART mode */
> + serial_write_reg(uart, UART_OMAP_MDR1, 0x00); /* UART 16x mode */
> + serial_write_reg(uart, UART_LCR, 0x80);
> + /* Enable internal loop back mode by setting MCR_REG[4].LOOPBACK_EN */
> + serial_write_reg(uart, UART_MCR, 0x10);
> +
> + /* write to THR,read RHR and compare */
> + /* Tx output is internally looped back to Rx input in loop back mode */
> + serial_write_reg(uart, UART_LCR_DLAB, 0x00);
> + /* Enables write to THR and read from RHR */
> + serial_write_reg(uart, UART_TX, 0xCC); /* writing data to THR */
> + /* reading data from RHR */
> + loopbk_rhr = (serial_read_reg(uart, UART_RX) & 0xFF);
> + if (loopbk_rhr == 0xCC) {
> + /* compare passes,try comparing with different data */
> + serial_write_reg(uart, UART_TX, 0x69);
> + loopbk_rhr = (serial_read_reg(uart, UART_RX) & 0xFF);
> + if (loopbk_rhr == 0x69) {
> + /* compare passes,reset UART3 and re-configure module */
> + omap_uart_reset(uart);
> + omap_uart_restore_context(uart);
> + return 0;
> + }
> + } else { /* requires warm reset */
> + return -ENODEV;
> + }
> + return 0;
> +}
> +
> +int omap_uart_per_errata(void)
> +{
> + struct omap_uart_state *uart;
> +
> + /* For all initialised UART modules that are in PER domain
> + * do loopback test
> + */
> + list_for_each_entry(uart, &uart_list, node) {
> + if (_is_per_uart(uart)) {
> + if (omap_uart_loopback_test(uart))
> + return -ENODEV;
> + else
> + return 0;
> + }
> + }
> + return 0;
> +}
> +
> #else
> static inline void omap_uart_save_context(struct omap_uart_state *uart) {}
> static inline void omap_uart_restore_context(struct omap_uart_state *uart) {}
> diff --git a/arch/arm/plat-omap/include/plat/serial.h b/arch/arm/plat-omap/include/plat/serial.h
> index 19145f5..81169b2 100644
> --- a/arch/arm/plat-omap/include/plat/serial.h
> +++ b/arch/arm/plat-omap/include/plat/serial.h
> @@ -102,6 +102,10 @@ extern void omap_uart_prepare_suspend(void);
> extern void omap_uart_prepare_idle(int num);
> extern void omap_uart_resume_idle(int num);
> extern void omap_uart_enable_irqs(int enable);
> +#ifdef CONFIG_PM
> +extern int omap_uart_per_errata(void);
> +extern int omap_uart_check_per_uarts_used(void);
> +#endif
> #endif
>
> #endif
Kevin
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