[PATCH] ARM: cpu: start: don't panic when only initial memory known

[PATCH] ARM: cpu: start: don't panic when only initial memory known

[Ahmad Fatoum]

Boards that get their memory from device tree are prone to breakage if
upstream decides to remove the /memory node or renders it unusable[0]
or to disable the DRAM controller device node[1] used to dynamically
compute the size.  While this needs to be fixed properly on a
case-by-case basis, soften the blow by using the memory size specified
by low level code as a fallback instead of just throwing the towel.

[0]: aa68c6bd3615 ("arm: rk3288-phycore-som: Fix memory node")
[1]: 0529149b2756 ("arm: imx8mq: re-enable DDRC for Barebox")
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
 arch/arm/cpu/mmu-common.c          | 15 +++++++++++++--
 arch/arm/cpu/start.c               |  8 ++++++++
 arch/arm/include/asm/barebox-arm.h |  1 +
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/arch/arm/cpu/mmu-common.c b/arch/arm/cpu/mmu-common.c
index 2ef1fa231f39..488a189f1c06 100644
--- a/arch/arm/cpu/mmu-common.c
+++ b/arch/arm/cpu/mmu-common.c
@@ -9,6 +9,7 @@
 #include <dma.h>
 #include <mmu.h>
 #include <asm/system.h>
+#include <asm/barebox-arm.h>
 #include <memory.h>
 #include "mmu.h"
 
@@ -58,14 +59,24 @@ void dma_free_coherent(void *mem, dma_addr_t dma_handle, size_t size)
 
 static int mmu_init(void)
 {
-	if (list_empty(&memory_banks))
+	if (list_empty(&memory_banks)) {
+		resource_size_t start;
+		int ret;
+
 		/*
 		 * If you see this it means you have no memory registered.
 		 * This can be done either with arm_add_mem_device() in an
 		 * initcall prior to mmu_initcall or via devicetree in the
 		 * memory node.
 		 */
-		panic("MMU: No memory bank found! Cannot continue\n");
+		pr_emerg("No memory bank registered. Limping along with initial memory\n");
+
+		start = arm_mem_membase_get();
+		ret = barebox_add_memory_bank("initmem", start,
+					      arm_mem_endmem_get() - start);
+		if (ret)
+			panic("");
+	}
 
 	__mmu_init(get_cr() & CR_M);
 
diff --git a/arch/arm/cpu/start.c b/arch/arm/cpu/start.c
index c61db668658b..14cc310312ab 100644
--- a/arch/arm/cpu/start.c
+++ b/arch/arm/cpu/start.c
@@ -28,6 +28,7 @@
 unsigned long arm_stack_top;
 static unsigned long arm_barebox_size;
 static unsigned long arm_endmem;
+static unsigned long arm_membase;
 static void *barebox_boarddata;
 static unsigned long barebox_boarddata_size;
 
@@ -114,6 +115,12 @@ unsigned long arm_mem_endmem_get(void)
 }
 EXPORT_SYMBOL_GPL(arm_mem_endmem_get);
 
+unsigned long arm_mem_membase_get(void)
+{
+	return arm_membase;
+}
+EXPORT_SYMBOL_GPL(arm_mem_membase_get);
+
 static int barebox_memory_areas_init(void)
 {
 	if(barebox_boarddata)
@@ -148,6 +155,7 @@ __noreturn __no_sanitize_address void barebox_non_pbl_start(unsigned long membas
 
 	pr_debug("memory at 0x%08lx, size 0x%08lx\n", membase, memsize);
 
+	arm_membase = membase;
 	arm_endmem = endmem;
 	arm_stack_top = arm_mem_stack_top(membase, endmem);
 	arm_barebox_size = barebox_size;
diff --git a/arch/arm/include/asm/barebox-arm.h b/arch/arm/include/asm/barebox-arm.h
index 15b3b6c44479..8240cce9bf5b 100644
--- a/arch/arm/include/asm/barebox-arm.h
+++ b/arch/arm/include/asm/barebox-arm.h
@@ -84,6 +84,7 @@ static inline void boarddata_create(void *adr, u32 machine)
 u32 barebox_arm_machine(void);
 
 unsigned long arm_mem_ramoops_get(void);
+unsigned long arm_mem_membase_get(void);
 unsigned long arm_mem_endmem_get(void);
 
 struct barebox_arm_boarddata *barebox_arm_get_boarddata(void);
-- 
2.30.2

Re: [PATCH] ARM: cpu: start: don't panic when only initial memory known

[Sascha Hauer]

On Wed, Jun 22, 2022 at 07:51:11PM +0200, Ahmad Fatoum wrote:
> Boards that get their memory from device tree are prone to breakage if
> upstream decides to remove the /memory node or renders it unusable[0]
> or to disable the DRAM controller device node[1] used to dynamically
> compute the size.  While this needs to be fixed properly on a
> case-by-case basis, soften the blow by using the memory size specified
> by low level code as a fallback instead of just throwing the towel.
> 
> [0]: aa68c6bd3615 ("arm: rk3288-phycore-som: Fix memory node")
> [1]: 0529149b2756 ("arm: imx8mq: re-enable DDRC for Barebox")
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  arch/arm/cpu/mmu-common.c          | 15 +++++++++++++--
>  arch/arm/cpu/start.c               |  8 ++++++++
>  arch/arm/include/asm/barebox-arm.h |  1 +
>  3 files changed, 22 insertions(+), 2 deletions(-)

Applied, thanks

Sascha

> 
> diff --git a/arch/arm/cpu/mmu-common.c b/arch/arm/cpu/mmu-common.c
> index 2ef1fa231f39..488a189f1c06 100644
> --- a/arch/arm/cpu/mmu-common.c
> +++ b/arch/arm/cpu/mmu-common.c
> @@ -9,6 +9,7 @@
>  #include <dma.h>
>  #include <mmu.h>
>  #include <asm/system.h>
> +#include <asm/barebox-arm.h>
>  #include <memory.h>
>  #include "mmu.h"
>  
> @@ -58,14 +59,24 @@ void dma_free_coherent(void *mem, dma_addr_t dma_handle, size_t size)
>  
>  static int mmu_init(void)
>  {
> -	if (list_empty(&memory_banks))
> +	if (list_empty(&memory_banks)) {
> +		resource_size_t start;
> +		int ret;
> +
>  		/*
>  		 * If you see this it means you have no memory registered.
>  		 * This can be done either with arm_add_mem_device() in an
>  		 * initcall prior to mmu_initcall or via devicetree in the
>  		 * memory node.
>  		 */
> -		panic("MMU: No memory bank found! Cannot continue\n");
> +		pr_emerg("No memory bank registered. Limping along with initial memory\n");
> +
> +		start = arm_mem_membase_get();
> +		ret = barebox_add_memory_bank("initmem", start,
> +					      arm_mem_endmem_get() - start);
> +		if (ret)
> +			panic("");
> +	}
>  
>  	__mmu_init(get_cr() & CR_M);
>  
> diff --git a/arch/arm/cpu/start.c b/arch/arm/cpu/start.c
> index c61db668658b..14cc310312ab 100644
> --- a/arch/arm/cpu/start.c
> +++ b/arch/arm/cpu/start.c
> @@ -28,6 +28,7 @@
>  unsigned long arm_stack_top;
>  static unsigned long arm_barebox_size;
>  static unsigned long arm_endmem;
> +static unsigned long arm_membase;
>  static void *barebox_boarddata;
>  static unsigned long barebox_boarddata_size;
>  
> @@ -114,6 +115,12 @@ unsigned long arm_mem_endmem_get(void)
>  }
>  EXPORT_SYMBOL_GPL(arm_mem_endmem_get);
>  
> +unsigned long arm_mem_membase_get(void)
> +{
> +	return arm_membase;
> +}
> +EXPORT_SYMBOL_GPL(arm_mem_membase_get);
> +
>  static int barebox_memory_areas_init(void)
>  {
>  	if(barebox_boarddata)
> @@ -148,6 +155,7 @@ __noreturn __no_sanitize_address void barebox_non_pbl_start(unsigned long membas
>  
>  	pr_debug("memory at 0x%08lx, size 0x%08lx\n", membase, memsize);
>  
> +	arm_membase = membase;
>  	arm_endmem = endmem;
>  	arm_stack_top = arm_mem_stack_top(membase, endmem);
>  	arm_barebox_size = barebox_size;
> diff --git a/arch/arm/include/asm/barebox-arm.h b/arch/arm/include/asm/barebox-arm.h
> index 15b3b6c44479..8240cce9bf5b 100644
> --- a/arch/arm/include/asm/barebox-arm.h
> +++ b/arch/arm/include/asm/barebox-arm.h
> @@ -84,6 +84,7 @@ static inline void boarddata_create(void *adr, u32 machine)
>  u32 barebox_arm_machine(void);
>  
>  unsigned long arm_mem_ramoops_get(void);
> +unsigned long arm_mem_membase_get(void);
>  unsigned long arm_mem_endmem_get(void);
>  
>  struct barebox_arm_boarddata *barebox_arm_get_boarddata(void);
> -- 
> 2.30.2
> 
> 
> 

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