* [PATCH/RFC] ARM: shmobile: LPAE memory bank CMA assignment prototype
@ 2015-12-19 1:40 Magnus Damm
2015-12-27 8:51 ` Laurent Pinchart
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: Magnus Damm @ 2015-12-19 1:40 UTC (permalink / raw)
To: linux-sh
From: Magnus Damm <damm+renesas@opensource.se>
This prototype patch extends the kernel to also reserve CMA memory
in the top memory bank on R-Car Gen2 boards and ties this larger
CMA area to the DU device for testing purpose.
This top portion of the memory requires 40-bits addressing support
in bus master devices including LPAE for the ARM CPU cores.
The patch assigns a 512 MiB CMA area to the DU device that may be
used with the IPMMU hardware to perform 40-bit bus master access.
Without IPMMU the DU hardware only supports 32-bit addresses.
Tested on r8a7791 Koelsch HDMI output using the modetest utility:
# modetest -M rcar-du -s 33:1024x768@AR24
Not for upstream merge.
Not-Yet-Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
---
arch/arm/mach-shmobile/setup-rcar-gen2.c | 33 ++++++++-
drivers/staging/board/Makefile | 1
drivers/staging/board/rcar-gen2.c | 104 ++++++++++++++++++++++++++++++
3 files changed, 134 insertions(+), 4 deletions(-)
--- 0001/arch/arm/mach-shmobile/setup-rcar-gen2.c
+++ work/arch/arm/mach-shmobile/setup-rcar-gen2.c 2015-12-19 09:38:09.750513000 +0900
@@ -136,14 +136,14 @@ struct memory_reserve_config {
u64 base, size;
};
-static int __init rcar_gen2_scan_mem(unsigned long node, const char *uname,
- int depth, void *data)
+static int __init __rcar_gen2_scan_mem(unsigned long node, const char *uname,
+ int depth, void *data,
+ u64 lpae_start)
{
const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
const __be32 *reg, *endp;
int l;
struct memory_reserve_config *mrc = data;
- u64 lpae_start = 1ULL << 32;
/* We are scanning "memory" nodes only */
if (type = NULL || strcmp(type, "memory"))
@@ -182,6 +182,20 @@ static int __init rcar_gen2_scan_mem(uns
return 0;
}
+static int __init rcar_gen2_scan_mem_legacy(unsigned long node,
+ const char *uname,
+ int depth, void *data)
+{
+ return __rcar_gen2_scan_mem(node, uname, depth, data, 1ULL << 32);
+}
+
+static int __init rcar_gen2_scan_mem_lpae(unsigned long node,
+ const char *uname,
+ int depth, void *data)
+{
+ return __rcar_gen2_scan_mem(node, uname, depth, data, 1ULL << 40);
+}
+
struct cma *rcar_gen2_dma_contiguous;
void __init rcar_gen2_reserve(void)
@@ -192,7 +206,18 @@ void __init rcar_gen2_reserve(void)
memset(&mrc, 0, sizeof(mrc));
mrc.reserved = SZ_256M;
- of_scan_flat_dt(rcar_gen2_scan_mem, &mrc);
+ of_scan_flat_dt(rcar_gen2_scan_mem_legacy, &mrc);
+#ifdef CONFIG_DMA_CMA
+ if (mrc.size && memblock_is_region_memory(mrc.base, mrc.size))
+ dma_contiguous_reserve_area(mrc.size, mrc.base, 0,
+ &rcar_gen2_dma_contiguous, true);
+#endif
+
+ /* reserve 512 MiB at the top of the 40-bit memory space */
+ memset(&mrc, 0, sizeof(mrc));
+ mrc.reserved = SZ_512M;
+
+ of_scan_flat_dt(rcar_gen2_scan_mem_lpae, &mrc);
#ifdef CONFIG_DMA_CMA
if (mrc.size && memblock_is_region_memory(mrc.base, mrc.size))
dma_contiguous_reserve_area(mrc.size, mrc.base, 0,
--- 0001/drivers/staging/board/Makefile
+++ work/drivers/staging/board/Makefile 2015-12-18 17:46:31.030513000 +0900
@@ -1,3 +1,4 @@
obj-y := board.o
obj-$(CONFIG_ARCH_EMEV2) += kzm9d.o
obj-$(CONFIG_ARCH_R8A7740) += armadillo800eva.o
+obj-$(CONFIG_ARCH_RCAR_GEN2) += rcar-gen2.o
--- /dev/null
+++ work/drivers/staging/board/rcar-gen2.c 2015-12-19 10:07:35.820513000 +0900
@@ -0,0 +1,104 @@
+/* Staging board support for R-Car Gen2. Enable not-yet-DT-capable bits here. */
+
+#include <linux/kernel.h>
+#include <linux/cma.h>
+#include <linux/dma-contiguous.h>
+#include <linux/errno.h>
+#include <linux/notifier.h>
+#include <linux/platform_device.h>
+#include "board.h"
+#include "../../../mm/cma.h"
+
+#if defined(CONFIG_CMA) && defined(CONFIG_DMA_CMA)
+
+static struct cma *largest_cma_area;
+
+static int cma_assign_bus_notifier(struct notifier_block *nb,
+ unsigned long action, void *data)
+{
+ struct device *dev = data;
+ const struct device_node *node = dev->of_node;
+
+ if (action = BUS_NOTIFY_BIND_DRIVER) {
+ if (of_device_is_compatible(node, "renesas,du-r8a7790") ||
+ of_device_is_compatible(node, "renesas,du-r8a7791") ||
+ of_device_is_compatible(node, "renesas,du-r8a7793") ||
+ of_device_is_compatible(node, "renesas,du-r8a7794")) {
+
+ pr_info("Board Staging: Assigning CMA to %s\n",
+ of_node_full_name(node));
+ dev_set_cma_area(dev, largest_cma_area);
+ }
+ }
+
+ return 0;
+}
+
+static struct notifier_block cma_assign_nb = {
+ .notifier_call = cma_assign_bus_notifier,
+};
+
+struct cma *find_largest_nondefault_cma(void)
+{
+ unsigned long largest_size;
+ int k, largest_idx;
+
+ largest_size = 0;
+ largest_idx = -ENOENT;
+
+ for (k = 0; k < cma_area_count; k++) {
+ if (&cma_areas[k] = dma_contiguous_default_area)
+ continue;
+
+ if (cma_get_size(&cma_areas[k]) > largest_size) {
+ largest_size = cma_get_size(&cma_areas[k]);
+ largest_idx = k;
+ }
+ }
+
+ if (largest_idx != -ENOENT)
+ return &cma_areas[largest_idx];
+
+ return NULL;
+}
+
+static void __init board_staging_init(void)
+{
+ struct cma *target;
+ phys_addr_t cma_base;
+
+ target = find_largest_nondefault_cma();
+
+ if (target) {
+ cma_base = cma_get_base(target);
+
+ pr_info("Board Staging: Located CMA at "
+ "%pa, size %ld MiB\n", &cma_base,
+ (unsigned long)cma_get_size(target) / SZ_1M);
+
+ largest_cma_area = target;
+ bus_register_notifier(&platform_bus_type, &cma_assign_nb);
+ }
+}
+#else
+static inline void __init board_staging_init(void) {}
+#endif
+
+static int __init runtime_board_check(void)
+{
+ if (of_machine_is_compatible("renesas,r8a7790"))
+ board_staging_init();
+
+ if (of_machine_is_compatible("renesas,r8a7791"))
+ board_staging_init();
+
+ if (of_machine_is_compatible("renesas,r8a7793"))
+ board_staging_init();
+
+ if (of_machine_is_compatible("renesas,r8a7794"))
+ board_staging_init();
+
+ return 0;
+}
+
+arch_initcall(runtime_board_check)
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH/RFC] ARM: shmobile: LPAE memory bank CMA assignment prototype
2015-12-19 1:40 [PATCH/RFC] ARM: shmobile: LPAE memory bank CMA assignment prototype Magnus Damm
@ 2015-12-27 8:51 ` Laurent Pinchart
2015-12-28 3:17 ` Magnus Damm
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Laurent Pinchart @ 2015-12-27 8:51 UTC (permalink / raw)
To: linux-sh
Hi Magnus,
Thank you for the patch.
On Saturday 19 December 2015 10:40:05 Magnus Damm wrote:
> From: Magnus Damm <damm+renesas@opensource.se>
>
> This prototype patch extends the kernel to also reserve CMA memory
> in the top memory bank on R-Car Gen2 boards and ties this larger
> CMA area to the DU device for testing purpose.
>
> This top portion of the memory requires 40-bits addressing support
> in bus master devices including LPAE for the ARM CPU cores.
>
> The patch assigns a 512 MiB CMA area to the DU device that may be
> used with the IPMMU hardware to perform 40-bit bus master access.
> Without IPMMU the DU hardware only supports 32-bit addresses.
>
> Tested on r8a7791 Koelsch HDMI output using the modetest utility:
> # modetest -M rcar-du -s 33:1024x768@AR24
>
> Not for upstream merge.
I tried to understand where the setup-rcar-gen2.c code you're patching came
from. Due to a rebase the commit message of 83850b04ae77 ("ARM: shmobile:
rcar-gen2: Update for of_get_flat_dt_prop() update") is incorrect, but I've
traced the original commit to ae8bf91c80b0 ("ARM: shmobile: Add shared R-Car
Gen2 CMA reservation code") in Simon's tree.
That patch doesn't look like a very good approach to me, and neither does this
one :-) drivers/staging/board is a hack, and we're starting to abuse it. I
don't want to see board code coming back through the back door. What's wrong
with just reserving memory in DT with the reserved-memory bindings and
assigning it to the DU ?
> Not-Yet-Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
> ---
>
> arch/arm/mach-shmobile/setup-rcar-gen2.c | 33 ++++++++-
> drivers/staging/board/Makefile | 1
> drivers/staging/board/rcar-gen2.c | 104 +++++++++++++++++++++++++++
> 3 files changed, 134 insertions(+), 4 deletions(-)
>
> --- 0001/arch/arm/mach-shmobile/setup-rcar-gen2.c
> +++ work/arch/arm/mach-shmobile/setup-rcar-gen2.c
> 2015-12-19 09:38:09.750513000 +0900
> @@ -136,14 +136,14 @@ struct memory_reserve_config
> {
> u64 base, size;
> };
>
> -static int __init rcar_gen2_scan_mem(unsigned long node, const char *uname,
> - int depth, void *data)
> +static int __init __rcar_gen2_scan_mem(unsigned long node, const char
> *uname,
> + int depth, void *data,
> + u64 lpae_start)
> {
> const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
> const __be32 *reg, *endp;
> int l;
> struct memory_reserve_config *mrc = data;
> - u64 lpae_start = 1ULL << 32;
>
> /* We are scanning "memory" nodes only */
> if (type = NULL || strcmp(type, "memory"))
> @@ -182,6 +182,20 @@ static int __init rcar_gen2_scan_mem(uns
> return 0;
> }
>
> +static int __init rcar_gen2_scan_mem_legacy(unsigned long node,
> + const char *uname,
> + int depth, void *data)
> +{
> + return __rcar_gen2_scan_mem(node, uname, depth, data, 1ULL << 32);
> +}
> +
> +static int __init rcar_gen2_scan_mem_lpae(unsigned long node,
> + const char *uname,
> + int depth, void *data)
> +{
> + return __rcar_gen2_scan_mem(node, uname, depth, data, 1ULL << 40);
> +}
> +
> struct cma *rcar_gen2_dma_contiguous;
>
> void __init rcar_gen2_reserve(void)
> @@ -192,7 +206,18 @@ void __init rcar_gen2_reserve(void)
> memset(&mrc, 0, sizeof(mrc));
> mrc.reserved = SZ_256M;
>
> - of_scan_flat_dt(rcar_gen2_scan_mem, &mrc);
> + of_scan_flat_dt(rcar_gen2_scan_mem_legacy, &mrc);
> +#ifdef CONFIG_DMA_CMA
> + if (mrc.size && memblock_is_region_memory(mrc.base, mrc.size))
> + dma_contiguous_reserve_area(mrc.size, mrc.base, 0,
> + &rcar_gen2_dma_contiguous, true);
> +#endif
> +
> + /* reserve 512 MiB at the top of the 40-bit memory space */
> + memset(&mrc, 0, sizeof(mrc));
> + mrc.reserved = SZ_512M;
> +
> + of_scan_flat_dt(rcar_gen2_scan_mem_lpae, &mrc);
> #ifdef CONFIG_DMA_CMA
> if (mrc.size && memblock_is_region_memory(mrc.base, mrc.size))
> dma_contiguous_reserve_area(mrc.size, mrc.base, 0,
> --- 0001/drivers/staging/board/Makefile
> +++ work/drivers/staging/board/Makefile 2015-12-18 17:46:31.030513000 +0900
> @@ -1,3 +1,4 @@
> obj-y := board.o
> obj-$(CONFIG_ARCH_EMEV2) += kzm9d.o
> obj-$(CONFIG_ARCH_R8A7740) += armadillo800eva.o
> +obj-$(CONFIG_ARCH_RCAR_GEN2) += rcar-gen2.o
> --- /dev/null
> +++ work/drivers/staging/board/rcar-gen2.c 2015-12-19 10:07:35.820513000
> +0900 @@ -0,0 +1,104 @@
> +/* Staging board support for R-Car Gen2. Enable not-yet-DT-capable bits
> here. */ +
> +#include <linux/kernel.h>
> +#include <linux/cma.h>
> +#include <linux/dma-contiguous.h>
> +#include <linux/errno.h>
> +#include <linux/notifier.h>
> +#include <linux/platform_device.h>
> +#include "board.h"
> +#include "../../../mm/cma.h"
> +
> +#if defined(CONFIG_CMA) && defined(CONFIG_DMA_CMA)
> +
> +static struct cma *largest_cma_area;
> +
> +static int cma_assign_bus_notifier(struct notifier_block *nb,
> + unsigned long action, void *data)
> +{
> + struct device *dev = data;
> + const struct device_node *node = dev->of_node;
> +
> + if (action = BUS_NOTIFY_BIND_DRIVER) {
> + if (of_device_is_compatible(node, "renesas,du-r8a7790") ||
> + of_device_is_compatible(node, "renesas,du-r8a7791") ||
> + of_device_is_compatible(node, "renesas,du-r8a7793") ||
> + of_device_is_compatible(node, "renesas,du-r8a7794")) {
> +
> + pr_info("Board Staging: Assigning CMA to %s\n",
> + of_node_full_name(node));
> + dev_set_cma_area(dev, largest_cma_area);
> + }
> + }
> +
> + return 0;
> +}
> +
> +static struct notifier_block cma_assign_nb = {
> + .notifier_call = cma_assign_bus_notifier,
> +};
> +
> +struct cma *find_largest_nondefault_cma(void)
> +{
> + unsigned long largest_size;
> + int k, largest_idx;
> +
> + largest_size = 0;
> + largest_idx = -ENOENT;
> +
> + for (k = 0; k < cma_area_count; k++) {
> + if (&cma_areas[k] = dma_contiguous_default_area)
> + continue;
> +
> + if (cma_get_size(&cma_areas[k]) > largest_size) {
> + largest_size = cma_get_size(&cma_areas[k]);
> + largest_idx = k;
> + }
> + }
> +
> + if (largest_idx != -ENOENT)
> + return &cma_areas[largest_idx];
> +
> + return NULL;
> +}
> +
> +static void __init board_staging_init(void)
> +{
> + struct cma *target;
> + phys_addr_t cma_base;
> +
> + target = find_largest_nondefault_cma();
> +
> + if (target) {
> + cma_base = cma_get_base(target);
> +
> + pr_info("Board Staging: Located CMA at "
> + "%pa, size %ld MiB\n", &cma_base,
> + (unsigned long)cma_get_size(target) / SZ_1M);
> +
> + largest_cma_area = target;
> + bus_register_notifier(&platform_bus_type, &cma_assign_nb);
> + }
> +}
> +#else
> +static inline void __init board_staging_init(void) {}
> +#endif
> +
> +static int __init runtime_board_check(void)
> +{
> + if (of_machine_is_compatible("renesas,r8a7790"))
> + board_staging_init();
> +
> + if (of_machine_is_compatible("renesas,r8a7791"))
> + board_staging_init();
> +
> + if (of_machine_is_compatible("renesas,r8a7793"))
> + board_staging_init();
> +
> + if (of_machine_is_compatible("renesas,r8a7794"))
> + board_staging_init();
> +
> + return 0;
> +}
> +
> +arch_initcall(runtime_board_check)
--
Regards,
Laurent Pinchart
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH/RFC] ARM: shmobile: LPAE memory bank CMA assignment prototype
2015-12-19 1:40 [PATCH/RFC] ARM: shmobile: LPAE memory bank CMA assignment prototype Magnus Damm
2015-12-27 8:51 ` Laurent Pinchart
@ 2015-12-28 3:17 ` Magnus Damm
2015-12-28 10:10 ` Laurent Pinchart
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: Magnus Damm @ 2015-12-28 3:17 UTC (permalink / raw)
To: linux-sh
Hi Laurent,
On Sun, Dec 27, 2015 at 5:51 PM, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
> Hi Magnus,
>
> Thank you for the patch.
>
> On Saturday 19 December 2015 10:40:05 Magnus Damm wrote:
>> From: Magnus Damm <damm+renesas@opensource.se>
>>
>> This prototype patch extends the kernel to also reserve CMA memory
>> in the top memory bank on R-Car Gen2 boards and ties this larger
>> CMA area to the DU device for testing purpose.
>>
>> This top portion of the memory requires 40-bits addressing support
>> in bus master devices including LPAE for the ARM CPU cores.
>>
>> The patch assigns a 512 MiB CMA area to the DU device that may be
>> used with the IPMMU hardware to perform 40-bit bus master access.
>> Without IPMMU the DU hardware only supports 32-bit addresses.
>>
>> Tested on r8a7791 Koelsch HDMI output using the modetest utility:
>> # modetest -M rcar-du -s 33:1024x768@AR24
>>
>> Not for upstream merge.
>
> I tried to understand where the setup-rcar-gen2.c code you're patching came
> from. Due to a rebase the commit message of 83850b04ae77 ("ARM: shmobile:
> rcar-gen2: Update for of_get_flat_dt_prop() update") is incorrect, but I've
> traced the original commit to ae8bf91c80b0 ("ARM: shmobile: Add shared R-Car
> Gen2 CMA reservation code") in Simon's tree.
Right, I recall adding that CMA reservation code.
> That patch doesn't look like a very good approach to me, and neither does this
> one :-) drivers/staging/board is a hack, and we're starting to abuse it.
At the time the Gen2 CMA reservation code was written there was no DT
memory reservation support available.
Regarding this patch, it is just a proof of concept to test allocation
from a high memory address without modifying any hardware description.
> I
> don't want to see board code coming back through the back door. What's wrong
> with just reserving memory in DT with the reserved-memory bindings and
> assigning it to the DU ?
Describing device-to-memory bank assignment in DT equals mixing
software policy with hardware description. I prefer to keep the
software policy in C and the hardware description in DT.
If you think there are better ways to reserve memory, why don't you
cook up a counter proposal and post it in a public space? =)
Thanks,
/ magnus
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH/RFC] ARM: shmobile: LPAE memory bank CMA assignment prototype
2015-12-19 1:40 [PATCH/RFC] ARM: shmobile: LPAE memory bank CMA assignment prototype Magnus Damm
2015-12-27 8:51 ` Laurent Pinchart
2015-12-28 3:17 ` Magnus Damm
@ 2015-12-28 10:10 ` Laurent Pinchart
2015-12-28 10:21 ` Geert Uytterhoeven
2015-12-28 10:24 ` Laurent Pinchart
4 siblings, 0 replies; 6+ messages in thread
From: Laurent Pinchart @ 2015-12-28 10:10 UTC (permalink / raw)
To: linux-sh
Hi Magnus,
On Monday 28 December 2015 12:17:15 Magnus Damm wrote:
> On Sun, Dec 27, 2015 at 5:51 PM, Laurent Pinchart wrote:
> > On Saturday 19 December 2015 10:40:05 Magnus Damm wrote:
> >> From: Magnus Damm <damm+renesas@opensource.se>
> >>
> >> This prototype patch extends the kernel to also reserve CMA memory
> >> in the top memory bank on R-Car Gen2 boards and ties this larger
> >> CMA area to the DU device for testing purpose.
> >>
> >> This top portion of the memory requires 40-bits addressing support
> >> in bus master devices including LPAE for the ARM CPU cores.
> >>
> >> The patch assigns a 512 MiB CMA area to the DU device that may be
> >> used with the IPMMU hardware to perform 40-bit bus master access.
> >> Without IPMMU the DU hardware only supports 32-bit addresses.
> >>
> >> Tested on r8a7791 Koelsch HDMI output using the modetest utility:
> >> # modetest -M rcar-du -s 33:1024x768@AR24
> >>
> >> Not for upstream merge.
> >
> > I tried to understand where the setup-rcar-gen2.c code you're patching
> > came from. Due to a rebase the commit message of 83850b04ae77 ("ARM:
> > shmobile: rcar-gen2: Update for of_get_flat_dt_prop() update") is
> > incorrect, but I've traced the original commit to ae8bf91c80b0 ("ARM:
> > shmobile: Add shared R-Car Gen2 CMA reservation code") in Simon's tree.
>
> Right, I recall adding that CMA reservation code.
>
> > That patch doesn't look like a very good approach to me, and neither does
> > this one :-) drivers/staging/board is a hack, and we're starting to abuse
> > it.
>
> At the time the Gen2 CMA reservation code was written there was no DT
> memory reservation support available.
Good point.
> Regarding this patch, it is just a proof of concept to test allocation
> from a high memory address without modifying any hardware description.
>
> > I don't want to see board code coming back through the back door. What's
> > wrong with just reserving memory in DT with the reserved-memory bindings
> > and assigning it to the DU ?
>
> Describing device-to-memory bank assignment in DT equals mixing
> software policy with hardware description. I prefer to keep the
> software policy in C and the hardware description in DT.
>
> If you think there are better ways to reserve memory, why don't you
> cook up a counter proposal and post it in a public space? =)
Doing it in DT is the better way in my opinion :-) There are established DT
bindings for that purpose, and that's what upstream is using.
--
Regards,
Laurent Pinchart
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH/RFC] ARM: shmobile: LPAE memory bank CMA assignment prototype
2015-12-19 1:40 [PATCH/RFC] ARM: shmobile: LPAE memory bank CMA assignment prototype Magnus Damm
` (2 preceding siblings ...)
2015-12-28 10:10 ` Laurent Pinchart
@ 2015-12-28 10:21 ` Geert Uytterhoeven
2015-12-28 10:24 ` Laurent Pinchart
4 siblings, 0 replies; 6+ messages in thread
From: Geert Uytterhoeven @ 2015-12-28 10:21 UTC (permalink / raw)
To: linux-sh
On Mon, Dec 28, 2015 at 11:10 AM, Laurent Pinchart
<laurent.pinchart@ideasonboard.com> wrote:
>> Regarding this patch, it is just a proof of concept to test allocation
>> from a high memory address without modifying any hardware description.
>>
>> > I don't want to see board code coming back through the back door. What's
>> > wrong with just reserving memory in DT with the reserved-memory bindings
>> > and assigning it to the DU ?
>>
>> Describing device-to-memory bank assignment in DT equals mixing
>> software policy with hardware description. I prefer to keep the
>> software policy in C and the hardware description in DT.
>>
>> If you think there are better ways to reserve memory, why don't you
>> cook up a counter proposal and post it in a public space? =)
>
> Doing it in DT is the better way in my opinion :-) There are established DT
> bindings for that purpose, and that's what upstream is using.
I'm a bit sceptical about describing this in DT, too, as this is a software
policy, not a hardware description, but it's indeed described in
Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH/RFC] ARM: shmobile: LPAE memory bank CMA assignment prototype
2015-12-19 1:40 [PATCH/RFC] ARM: shmobile: LPAE memory bank CMA assignment prototype Magnus Damm
` (3 preceding siblings ...)
2015-12-28 10:21 ` Geert Uytterhoeven
@ 2015-12-28 10:24 ` Laurent Pinchart
4 siblings, 0 replies; 6+ messages in thread
From: Laurent Pinchart @ 2015-12-28 10:24 UTC (permalink / raw)
To: linux-sh
Hi Geert,
On Monday 28 December 2015 11:21:08 Geert Uytterhoeven wrote:
> On Mon, Dec 28, 2015 at 11:10 AM, Laurent Pinchart wrote:
> >> Regarding this patch, it is just a proof of concept to test allocation
> >> from a high memory address without modifying any hardware description.
> >>
> >> > I don't want to see board code coming back through the back door.
> >> > What's wrong with just reserving memory in DT with the reserved-memory
> >> > bindings and assigning it to the DU ?
> >>
> >> Describing device-to-memory bank assignment in DT equals mixing
> >> software policy with hardware description. I prefer to keep the
> >> software policy in C and the hardware description in DT.
> >>
> >> If you think there are better ways to reserve memory, why don't you
> >> cook up a counter proposal and post it in a public space? =)
> >
> > Doing it in DT is the better way in my opinion :-) There are established
> > DT bindings for that purpose, and that's what upstream is using.
>
> I'm a bit sceptical about describing this in DT, too, as this is a software
> policy, not a hardware description, but it's indeed described in
> Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt
The idea of a DT-like kernel configuration file has been toyed with in the
past but as far as I know it got abandoned. It was certainly an interesting
idea, and could possibly have led to a better solution, but today what we have
is DT. Board files are not the way to go to implement such a feature.
--
Regards,
Laurent Pinchart
^ permalink raw reply [flat|nested] 6+ messages in thread
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2015-12-19 1:40 [PATCH/RFC] ARM: shmobile: LPAE memory bank CMA assignment prototype Magnus Damm
2015-12-27 8:51 ` Laurent Pinchart
2015-12-28 3:17 ` Magnus Damm
2015-12-28 10:10 ` Laurent Pinchart
2015-12-28 10:21 ` Geert Uytterhoeven
2015-12-28 10:24 ` Laurent Pinchart
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