Subject: Re: [PATCH 4/4] powerpc/mm: Update the HID bit when switching from radix to hash

From: Michael Neuling <[email-masked]>
Date: Tue, 06 Sep 2016 11:18:41 +1000

On Wed, 2016-08-24 at 15:03 +0530, Aneesh Kumar K.V wrote:
> Power9 DD1 requires to update the hid0 register when switching from
> hash to radix.

One minor nit.  This is bidirectional not just "hash to radix"

Could just be:

powerpc/mm: Update the HID bit when switching MMU modes

Power9 DD1 requires an update to the HID0 register when switching 
MMU modes ie. radix <-> hash.

Otherwise...

> Signed-off-by: Aneesh Kumar K.V <[email-masked]>

Acked-by: Michael Neuling <[email-masked]>

> ---
>  arch/powerpc/include/asm/reg.h  |  3 +++
>  arch/powerpc/mm/hash_utils_64.c | 25 +++++++++++++++++++++++++
>  arch/powerpc/mm/pgtable-radix.c | 28 ++++++++++++++++++++++++++++
>  3 files changed, 56 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
> index f69f40f1519a..9dddabc2fced 100644
> --- a/arch/powerpc/include/asm/reg.h
> +++ b/arch/powerpc/include/asm/reg.h
> @@ -475,6 +475,9 @@
>  #define HID0_POWER8_1TO4LPAR	__MASK(51)
>  #define HID0_POWER8_DYNLPARDIS	__MASK(48)
>  
> +/* POWER9 HID0 bits */
> +#define HID0_POWER9_RADIX	__MASK(63 - 8)
> +
>  #define SPRN_HID1	0x3F1		/* Hardware Implementation Register 1 */
>  #ifdef CONFIG_6xx
>  #define HID1_EMCP	(1<<31)		/* 7450 Machine Check Pin Enable */
> diff --git a/arch/powerpc/mm/hash_utils_64.c b/arch/powerpc/mm/hash_utils_64.c
> index 0821556e16f4..35a6721b3d25 100644
> --- a/arch/powerpc/mm/hash_utils_64.c
> +++ b/arch/powerpc/mm/hash_utils_64.c
> @@ -711,6 +711,29 @@ int remove_section_mapping(unsigned long start, unsigned long end)
>  }
>  #endif /* CONFIG_MEMORY_HOTPLUG */
>  
> +static void update_hid_for_hash(void)
> +{
> +	unsigned long hid0;
> +	unsigned long rb = 3UL << PPC_BITLSHIFT(53); /* IS = 3 */
> +
> +	asm volatile("ptesync": : :"memory");
> +	/* prs = 0, ric = 2, rs = 0, r = 1 is = 3 */
> +	asm volatile(PPC_TLBIE_5(%0, %4, %3, %2, %1)
> +		     : : "r"(rb), "i"(0), "i"(0), "i"(2), "r"(0) : "memory");
> +	asm volatile("eieio; tlbsync; ptesync; isync; slbia": : :"memory");
> +	/*
> +	 * now switch the HID
> +	 */
> +	hid0  = mfspr(SPRN_HID0);
> +	hid0 &= ~HID0_POWER9_RADIX;
> +	mtspr(SPRN_HID0, hid0);
> +	asm volatile("isync": : :"memory");
> +
> +	/* Wait for it to happen */
> +	while ((mfspr(SPRN_HID0) & HID0_POWER9_RADIX))
> +		cpu_relax();
> +}
> +
>  static void __init hash_init_partition_table(phys_addr_t hash_table,
>  					     unsigned long htab_size)
>  {
> @@ -737,6 +760,8 @@ static void __init hash_init_partition_table(phys_addr_t hash_table,
>  	 */
>  	partition_tb->patb1 = 0;
>  	pr_info("Partition table %p\n", partition_tb);
> +	if (cpu_has_feature(CPU_FTR_POWER9_DD1))
> +		update_hid_for_hash();
>  	/*
>  	 * update partition table control register,
>  	 * 64 K size.
> diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c
> index af897d91d09f..8f086352e421 100644
> --- a/arch/powerpc/mm/pgtable-radix.c
> +++ b/arch/powerpc/mm/pgtable-radix.c
> @@ -294,6 +294,32 @@ found:
>  	return;
>  }
>  
> +static void update_hid_for_radix(void)
> +{
> +	unsigned long hid0;
> +	unsigned long rb = 3UL << PPC_BITLSHIFT(53); /* IS = 3 */
> +
> +	asm volatile("ptesync": : :"memory");
> +	/* prs = 0, ric = 2, rs = 0, r = 1 is = 3 */
> +	asm volatile(PPC_TLBIE_5(%0, %4, %3, %2, %1)
> +		     : : "r"(rb), "i"(1), "i"(0), "i"(2), "r"(0) : "memory");
> +	/* prs = 1, ric = 2, rs = 0, r = 1 is = 3 */
> +	asm volatile(PPC_TLBIE_5(%0, %4, %3, %2, %1)
> +		     : : "r"(rb), "i"(1), "i"(1), "i"(2), "r"(0) : "memory");
> +	asm volatile("eieio; tlbsync; ptesync; isync; slbia": : :"memory");
> +	/*
> +	 * now switch the HID
> +	 */
> +	hid0  = mfspr(SPRN_HID0);
> +	hid0 |= HID0_POWER9_RADIX;
> +	mtspr(SPRN_HID0, hid0);
> +	asm volatile("isync": : :"memory");
> +
> +	/* Wait for it to happen */
> +	while (!(mfspr(SPRN_HID0) & HID0_POWER9_RADIX))
> +		cpu_relax();
> +}
> +
>  void __init radix__early_init_mmu(void)
>  {
>  	unsigned long lpcr;
> @@ -345,6 +371,8 @@ void __init radix__early_init_mmu(void)
>  
>  	if (!firmware_has_feature(FW_FEATURE_LPAR)) {
>  		radix_init_native();
> +		if (cpu_has_feature(CPU_FTR_POWER9_DD1))
> +			update_hid_for_radix();
>  		lpcr = mfspr(SPRN_LPCR);
>  		mtspr(SPRN_LPCR, lpcr | LPCR_UPRT | LPCR_HR);
>  		radix_init_partition_table();