ARM: 6984/1: enhance TCM robustness

The PB11MPCore reports "3" DTCM banks, but anything above 2 is an
"undefined" value, so push this to become 0. Further add some checks
if code is compiled to TCM even if there is no D/ITCM present in the
system, and if we can really fit the compiled code. We don't do the
BUG() since it's not helpful, it's better to deal with non-present
TCM dynamically. If there is nothing compiled to the TCM and no TCM
is detected, it will now just shut up even if TCM support is enabled.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 39 insertions, 8 deletions

diff --git a/arch/arm/kernel/tcm.c b/arch/arm/kernel/tcm.c
index f5cf660eefcc..d402d4829524 100644
--- a/arch/arm/kernel/tcm.c
+++ b/arch/arm/kernel/tcm.c
@@ -134,6 +134,10 @@ static int __init setup_tcm_bank(u8 type, u8 bank, u8 banks,
                         (tcm_region & 1) ? "" : "not ");
         }
 
+        /* Not much fun you can do with a size 0 bank */
+        if (tcm_size == 0)
+                return 0;
+
         /* Force move the TCM bank to where we want it, enable */
         tcm_region = *offset | (tcm_region & 0x00000ffeU) | 1;
 
@@ -165,12 +169,20 @@ void __init tcm_init(void)
         u32 tcm_status = read_cpuid_tcmstatus();
         u8 dtcm_banks = (tcm_status >> 16) & 0x03;
         u8 itcm_banks = (tcm_status & 0x03);
+        size_t dtcm_code_sz = &__edtcm_data - &__sdtcm_data;
+        size_t itcm_code_sz = &__eitcm_text - &__sitcm_text;
         char *start;
         char *end;
         char *ram;
         int ret;
         int i;
 
+        /* Values greater than 2 for D/ITCM banks are "reserved" */
+        if (dtcm_banks > 2)
+                dtcm_banks = 0;
+        if (itcm_banks > 2)
+                itcm_banks = 0;
+
         /* Setup DTCM if present */
         if (dtcm_banks > 0) {
                 for (i = 0; i < dtcm_banks; i++) {
@@ -178,6 +190,13 @@ void __init tcm_init(void)
                         if (ret)
                                 return;
                 }
+                /* This means you compiled more code than fits into DTCM */
+                if (dtcm_code_sz > (dtcm_end - DTCM_OFFSET)) {
+                        pr_info("CPU DTCM: %u bytes of code compiled to "
+                                "DTCM but only %lu bytes of DTCM present\n",
+                                dtcm_code_sz, (dtcm_end - DTCM_OFFSET));
+                        goto no_dtcm;
+                }
                 dtcm_res.end = dtcm_end - 1;
                 request_resource(&iomem_resource, &dtcm_res);
                 dtcm_iomap[0].length = dtcm_end - DTCM_OFFSET;
@@ -186,12 +205,15 @@ void __init tcm_init(void)
                 start = &__sdtcm_data;
                 end   = &__edtcm_data;
                 ram   = &__dtcm_start;
-                /* This means you compiled more code than fits into DTCM */
-                BUG_ON((end - start) > (dtcm_end - DTCM_OFFSET));
-                memcpy(start, ram, (end-start));
-                pr_debug("CPU DTCM: copied data from %p - %p\n", start, end);
+                memcpy(start, ram, dtcm_code_sz);
+                pr_debug("CPU DTCM: copied data from %p - %p\n",
+                         start, end);
+        } else if (dtcm_code_sz) {
+                pr_info("CPU DTCM: %u bytes of code compiled to DTCM but no "
+                        "DTCM banks present in CPU\n", dtcm_code_sz);
         }
 
+no_dtcm:
         /* Setup ITCM if present */
         if (itcm_banks > 0) {
                 for (i = 0; i < itcm_banks; i++) {
@@ -199,6 +221,13 @@ void __init tcm_init(void)
                         if (ret)
                                 return;
                 }
+                /* This means you compiled more code than fits into ITCM */
+                if (itcm_code_sz > (itcm_end - ITCM_OFFSET)) {
+                        pr_info("CPU ITCM: %u bytes of code compiled to "
+                                "ITCM but only %lu bytes of ITCM present\n",
+                                itcm_code_sz, (itcm_end - ITCM_OFFSET));
+                        return;
+                }
                 itcm_res.end = itcm_end - 1;
                 request_resource(&iomem_resource, &itcm_res);
                 itcm_iomap[0].length = itcm_end - ITCM_OFFSET;
@@ -207,10 +236,12 @@ void __init tcm_init(void)
                 start = &__sitcm_text;
                 end   = &__eitcm_text;
                 ram   = &__itcm_start;
-                /* This means you compiled more code than fits into ITCM */
-                BUG_ON((end - start) > (itcm_end - ITCM_OFFSET));
-                memcpy(start, ram, (end-start));
-                pr_debug("CPU ITCM: copied code from %p - %p\n", start, end);
+                memcpy(start, ram, itcm_code_sz);
+                pr_debug("CPU ITCM: copied code from %p - %p\n",
+                         start, end);
+        } else if (itcm_code_sz) {
+                pr_info("CPU ITCM: %u bytes of code compiled to ITCM but no "
+                        "ITCM banks present in CPU\n", itcm_code_sz);
         }
 }