[FAQ] PROCESSOR-SDK-AM57X: U-boot patch for Linux addressing AM57xx errata i2446

Setup

• The patch is implemented from u-boot source and utilizes EDMA3 driver. – drivers/dma/ti-edma3.c

• This driver is enabled by enabling TI_QSPI, which should be enabled by default in defconfig file – am57xx_evm_defconfig Implementation

Procedure

• It uses the EDMA3 API to make a single 16-Byte transfer to both PRU-ICSS clk registers, enabling them one after the other

• Based on usage example with QSPI: drivers/spi/ti_qspi.c::ti_qspi_copy_mmap()

• EDMA3_transfer transfers 16 bytes from OCM memory to CM_L4PER2_PRUSS1_CLKCTRL and CM_L4PER2_PRUSS2_CLKCTRL registers under 20 ns.

Patch

Patch originally made for ti-u-boot-2019.01

diff --git a/arch/arm/mach-omap2/omap5/hw_data.c b/arch/arm/mach-omap2/omap5/hw_data.c
index 955e721682..727235cee1 100644
--- a/arch/arm/mach-omap2/omap5/hw_data.c
+++ b/arch/arm/mach-omap2/omap5/hw_data.c
@@ -8,6 +8,7 @@
  *
  * Sricharan R <r.sricharan@ti.com>
  */
+
 #include <common.h>
 #include <palmas.h>
 #include <asm/arch/omap.h>
@@ -17,6 +18,7 @@
 #include <asm/omap_gpio.h>
 #include <asm/io.h>
 #include <asm/emif.h>
+#include <asm/ti-common/ti-edma3.h>
 
 struct prcm_regs const **prcm =
 			(struct prcm_regs const **) OMAP_SRAM_SCRATCH_PRCM_PTR;
@@ -516,6 +518,34 @@ void enable_basic_clocks(void)
 			OPTFCLKEN_SCRM_CORE_MASK);
 }
 
+#if defined(CONFIG_DRA7XX)
+static void do_edma3_copy(void *addrs, void *src_data, size_t len)
+{
+	unsigned int			edma_slot_num = 1;
+
+	/* enable edma3 clocks */
+	enable_edma3_clocks();
+
+	/* Call edma3 api to do actual DMA transfer	*/
+	edma3_transfer(EDMA3_BASE, edma_slot_num, addrs, src_data, len);
+
+	/* disable edma3 clocks */
+	disable_edma3_clocks();
+}
+#endif
+
+#if defined(CONFIG_DRA7XX)
+void do_enable_pruss_clocks(void)
+{
+	unsigned int *address = (unsigned int *) 0x4A009718;
+
+	unsigned int data[4] = {0x2,0x0,0x2,0x0};
+
+	do_edma3_copy(address,data,16);
+
+}
+#endif
+
 void enable_basic_uboot_clocks(void)
 {
 	u32 const clk_domains_essential[] = {
@@ -548,6 +578,10 @@ void enable_basic_uboot_clocks(void)
 			 clk_modules_hw_auto_essential,
 			 clk_modules_explicit_en_essential,
 			 1);
+
+#if defined(CONFIG_DRA7XX)
+	do_enable_pruss_clocks();
+#endif
 }
 
 #ifdef CONFIG_TI_EDMA3

Test for this failure

In order to verify that this errata is indeed what is causing the A15 to crash, one can test this at u-boot prompt using memory dumps to access the PRUSS global counters:

– PRUSS_IEP_GLOBAL_CFG (PRUSS1_IEP)

– PRUSS_IEP_GLOBAL_CFG (PRUSS2_IEP)

U-Boot Prompt

=> md.l 0x4B22E000 1

=> md.l 0x4B2AE000 1

Example: