Drop redundant boot_cpu_type in arch_sync_dma_for_cpu_all. These needs
to be parsed only once and we can make use of bmips_rac_flush_disable to
disable RAC flush on unsupported CPU.

Set this value in bmips_cpu_setup for unsupported CPU to skip this
redundant check every time DMA needs to be synced.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 arch/mips/bmips/dma.c         | 5 -----
 arch/mips/bmips/setup.c       | 1 -
 arch/mips/include/asm/bmips.h | 1 +
 arch/mips/kernel/smp-bmips.c  | 7 +++++++
 4 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/arch/mips/bmips/dma.c b/arch/mips/bmips/dma.c
index 799cc3e12fc3..e9af34f82dcd 100644
--- a/arch/mips/bmips/dma.c
+++ b/arch/mips/bmips/dma.c
@@ -11,11 +11,6 @@ void arch_sync_dma_for_cpu_all(void)
 {
 	u32 cfg;
 
-	if (boot_cpu_type() != CPU_BMIPS3300 &&
-	    boot_cpu_type() != CPU_BMIPS4350 &&
-	    boot_cpu_type() != CPU_BMIPS4380)
-		return;
-
 	if (unlikely(bmips_rac_flush_disable))
 		return;
 
diff --git a/arch/mips/bmips/setup.c b/arch/mips/bmips/setup.c
index bef84677248e..d27043b10405 100644
--- a/arch/mips/bmips/setup.c
+++ b/arch/mips/bmips/setup.c
@@ -40,7 +40,6 @@
  * with "mips-cbr-reg" in the "cpus" node.
  */
 void __iomem *bmips_cbr_addr;
-extern bool bmips_rac_flush_disable;
 
 static const unsigned long kbase = VMLINUX_LOAD_ADDRESS & 0xfff00000;
 
diff --git a/arch/mips/include/asm/bmips.h b/arch/mips/include/asm/bmips.h
index 3a1cdfddb987..4a48c8f1077e 100644
--- a/arch/mips/include/asm/bmips.h
+++ b/arch/mips/include/asm/bmips.h
@@ -82,6 +82,7 @@ extern char bmips_smp_int_vec[];
 extern char bmips_smp_int_vec_end[];
 
 extern void __iomem *bmips_cbr_addr;
+extern bool bmips_rac_flush_disable;
 extern int bmips_smp_enabled;
 extern int bmips_cpu_offset;
 extern cpumask_t bmips_booted_mask;
diff --git a/arch/mips/kernel/smp-bmips.c b/arch/mips/kernel/smp-bmips.c
index 7bde6bbaa41f..63534af367c7 100644
--- a/arch/mips/kernel/smp-bmips.c
+++ b/arch/mips/kernel/smp-bmips.c
@@ -681,6 +681,13 @@ void bmips_cpu_setup(void)
 		"	or	$8, $9\n"
 		"	.word	0x4088b008\n"	/* mtc0 $8, $22, 8 */
 		: : : "$8", "$9");
+
+		/* Disable RAC flush as not supported */
+		bmips_rac_flush_disable = true;
 		break;
+
+	default:
+		/* Disable RAC flush as not supported */
+		bmips_rac_flush_disable = true;
 	}
 }
-- 
2.43.0

On 5/3/24 06:54, Christian Marangi wrote:
> Drop redundant boot_cpu_type in arch_sync_dma_for_cpu_all. These needs
> to be parsed only once and we can make use of bmips_rac_flush_disable to
> disable RAC flush on unsupported CPU.
> 
> Set this value in bmips_cpu_setup for unsupported CPU to skip this
> redundant check every time DMA needs to be synced.
> 
> Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>

You are taking a shortcut that is reasonable in premise, but keying off 
the bmips_rac_flush_disable is IMHO misleading. The RAC is enabled in 
the BMIPS5000 and BMIPS5200 cores, just it does not need SW management 
unlike earlier cores.

If you renamed it to bmips_rac_flush_needed that might be more 
compelling. Also, the other reason is that on a kernel that was 
configured for supporting only BMIPS5000 and BMIPS5200 CPUs, I think we 
could get some decent dead code elimination of the boot_cpu_type() 
check, which would not be the case.
-- 
Florian

On Fri, May 03, 2024 at 12:07:45PM -0700, Florian Fainelli wrote:
> On 5/3/24 06:54, Christian Marangi wrote:
> > Drop redundant boot_cpu_type in arch_sync_dma_for_cpu_all. These needs
> > to be parsed only once and we can make use of bmips_rac_flush_disable to
> > disable RAC flush on unsupported CPU.
> > 
> > Set this value in bmips_cpu_setup for unsupported CPU to skip this
> > redundant check every time DMA needs to be synced.
> > 
> > Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
> 
> You are taking a shortcut that is reasonable in premise, but keying off the
> bmips_rac_flush_disable is IMHO misleading. The RAC is enabled in the
> BMIPS5000 and BMIPS5200 cores, just it does not need SW management unlike
> earlier cores.
> 
> If you renamed it to bmips_rac_flush_needed that might be more compelling.
> Also, the other reason is that on a kernel that was configured for
> supporting only BMIPS5000 and BMIPS5200 CPUs, I think we could get some
> decent dead code elimination of the boot_cpu_type() check, which would not
> be the case.

I was a bit confused by the last part, should I drop this or just rename
the variable? Cause I think for kernel that support ONLY those CPU I
guess the DMA function will be optimized anyway since the bool will
always be false I guess?

-- 
	Ansuel

On 5/3/24 12:39, Christian Marangi wrote:
> On Fri, May 03, 2024 at 12:07:45PM -0700, Florian Fainelli wrote:
>> On 5/3/24 06:54, Christian Marangi wrote:
>>> Drop redundant boot_cpu_type in arch_sync_dma_for_cpu_all. These needs
>>> to be parsed only once and we can make use of bmips_rac_flush_disable to
>>> disable RAC flush on unsupported CPU.
>>>
>>> Set this value in bmips_cpu_setup for unsupported CPU to skip this
>>> redundant check every time DMA needs to be synced.
>>>
>>> Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
>>
>> You are taking a shortcut that is reasonable in premise, but keying off the
>> bmips_rac_flush_disable is IMHO misleading. The RAC is enabled in the
>> BMIPS5000 and BMIPS5200 cores, just it does not need SW management unlike
>> earlier cores.
>>
>> If you renamed it to bmips_rac_flush_needed that might be more compelling.
>> Also, the other reason is that on a kernel that was configured for
>> supporting only BMIPS5000 and BMIPS5200 CPUs, I think we could get some
>> decent dead code elimination of the boot_cpu_type() check, which would not
>> be the case.
> 
> I was a bit confused by the last part, should I drop this or just rename
> the variable? Cause I think for kernel that support ONLY those CPU I
> guess the DMA function will be optimized anyway since the bool will
> always be false I guess?

I don't think it can be optimized, I would drop that patch. This is a 
hot-path and so any optimization is welcome.
-- 
Florian

On Fri, May 03, 2024 at 03:54:06PM +0200, Christian Marangi wrote:
> Drop redundant boot_cpu_type in arch_sync_dma_for_cpu_all. These needs
> to be parsed only once and we can make use of bmips_rac_flush_disable to
> disable RAC flush on unsupported CPU.
> 
> Set this value in bmips_cpu_setup for unsupported CPU to skip this
> redundant check every time DMA needs to be synced.
> 
> Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>

Sent by mistake please ignore and use the other PATCH 6/6 patch. (wrong commit title)

-- 
	Ansuel