This patch adds comments on precatution to be taken if Global Warm reset is used as the means to trigger sysem reset. Signed-off-by: Vishwanath BS <vishwanath.bs@xxxxxx> Cc: Paul Walmsley <paul@xxxxxxxxx> --- arch/arm/mach-omap2/prcm.c | 28 ++++++++++++++++++++++++++++ 1 files changed, 28 insertions(+), 0 deletions(-) diff --git a/arch/arm/mach-omap2/prcm.c b/arch/arm/mach-omap2/prcm.c index c201374..6494a88 --- a/arch/arm/mach-omap2/prcm.c +++ b/arch/arm/mach-omap2/prcm.c @@ -157,6 +157,34 @@ void omap_prcm_arch_reset(char mode, const char *cmd) else WARN_ON(1); + /* + * As per Errata i520, In some cases, user will not be able to + * access DDR memory after warm-reset. + * This situation occurs while the warm-reset happens during a read + * access to DDR memory. In that particular condition, DDR memory + * does not respond to a corrupted read command due to the warm + * reset occurence but SDRC is waiting for read completion. + * SDRC is not sensitive to the warm reset, but the interconect is + * reset on the fly, thus causing a misalignment between SDRC logic, + * interconect logic and DDR memory state. + * WORKAROUND: + * Steps to perform before a Warm reset is trigged: + * 1. enable self-refresh on idle request + * 2. put SDRC in idle + * 3. wait until SDRC goes to idle + * 4. generate SW reset (Global SW reset) + + * Steps to be performed after warm reset occurs (in bootloader): + * if HW warm reset is the source, apply below steps before any + * accesses to SDRAM: + * 1. Reset SMS and SDRC and wait till reset is complete + * 2. Re-initialize SMS, SDRC and memory + + * NOTE: Above work around is required only if arch reset is implemented + * using Global SW reset(GLOBAL_SW_RST). DPLL3 reset does not need + * the WA since it resets SDRC as well as part of cold reset. + */ + if (cpu_is_omap24xx() || cpu_is_omap34xx()) prm_set_mod_reg_bits(OMAP_RST_DPLL3_MASK, prcm_offs, OMAP2_RM_RSTCTRL); -- 1.7.0.4 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
