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>

diff --git a/arch/arm/kernel/tcm.c b/arch/arm/kernel/tcm.c
index f5cf660eefccda61515b0f33a56db0bf692d3b51..d402d4829524f6003060826500110ea96ebc5a34 100644 (file)
--- 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);
        }
 }