From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 5ABEEB6FA4 for ; Wed, 15 Jun 2011 20:12:11 +1000 (EST) Subject: Re: Relocatable kernel for ppc44x From: Benjamin Herrenschmidt To: Suzuki Poulose In-Reply-To: <4DF84D92.2030803@in.ibm.com> References: <4DF74E5D.9020908@monstr.eu> <4DF84D92.2030803@in.ibm.com> Content-Type: text/plain; charset="UTF-8" Date: Wed, 15 Jun 2011 20:11:55 +1000 Message-ID: <1308132715.2516.1.camel@pasglop> Mime-Version: 1.0 Cc: linuxppc-dev@ozlabs.org, monstr@monstr.eu, John Williams List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2011-06-15 at 11:43 +0530, Suzuki Poulose wrote: > On 06/14/11 17:34, Michal Simek wrote: > > Hi, > > > > have someone tried to support RELOCATABLE kernel on ppc44x? > As Josh, mentioned, I will be working on this. In fact I was trying a couple of > patches towards this on PPC440x. But, I am stuck in debugging the hang that I am > experiencing with the changes. I am setting up a RISCWatch processor probe to > debug the same. > > Here is some information that I wanted to share : > > The PPC440X currently uses 256M TLB entries to pin the lowmem. When we go for a > relocatable kernel we have to : > > 1) Restrict the kernel load address to be 256M aligned Wait a minute ... :-) There's a difference between having the kernel run from any address and mapping the linear mapping not starting at 0. Those are completely orthogonal. I don't see why off hand you are changing the way the TLB is used. The only possible change needed is to make sure the initial bolted entry set by the asm code properly covers the kernel in whatever it's "current" location is. The rest is a matter of fixing up the relocations... Cheers, Ben. > OR > > 2) Use 16M TLB(the next possible TLB page size supported) entries till the first > 256M and then use the 256M TLB entries for the rest of lowmem. > > Option 1 is not feasible. > > Towards this, I have tried a patch which uses 16M TLB entries to map the entire > lowmem on an ebony board. But that doesn't seem to work. I am setting up the JTAG > to debug the state. > > I have attached the patch below for your reference. Any suggestions/comments would > be really helpful. > > > Thanks > Suzuki > > ============================== > > > Use 16M TLB pages to pin the lowmem on PPC440x. > > --- > arch/powerpc/include/asm/mmu-44x.h | 9 +++++++++ > arch/powerpc/kernel/head_44x.S | 2 +- > arch/powerpc/mm/44x_mmu.c | 2 +- > 3 files changed, 11 insertions(+), 2 deletions(-) > > Index: linux-2.6.38.1/arch/powerpc/include/asm/mmu-44x.h > =================================================================== > --- linux-2.6.38.1.orig/arch/powerpc/include/asm/mmu-44x.h > +++ linux-2.6.38.1/arch/powerpc/include/asm/mmu-44x.h > @@ -121,7 +121,12 @@ typedef struct { > #endif > > /* Size of the TLBs used for pinning in lowmem */ > +#define PPC_PIN_SIZE (1 << 24) /* 16M */ > +#define PPC44x_TLB_PIN_SIZE PPC44x_TLB_16M > +#if 0 > #define PPC_PIN_SIZE (1 << 28) /* 256M */ > +#define PPC44x_TLB_PIN_SIZE PPC44x_TLB_256M > +#endif > > #if (PAGE_SHIFT == 12) > #define PPC44x_TLBE_SIZE PPC44x_TLB_4K > @@ -142,7 +147,11 @@ typedef struct { > #error "Unsupported PAGE_SIZE" > #endif > > +#if 0 > #define mmu_linear_psize MMU_PAGE_256M > +#else > +#define mmu_linear_psize MMU_PAGE_16M > +#endif > > #define PPC44x_PGD_OFF_SHIFT (32 - PGDIR_SHIFT + PGD_T_LOG2) > #define PPC44x_PGD_OFF_MASK_BIT (PGDIR_SHIFT - PGD_T_LOG2) > Index: linux-2.6.38.1/arch/powerpc/kernel/head_44x.S > =================================================================== > --- linux-2.6.38.1.orig/arch/powerpc/kernel/head_44x.S > +++ linux-2.6.38.1/arch/powerpc/kernel/head_44x.S > @@ -805,7 +805,7 @@ skpinv: addi r4,r4,1 /* Increment */ > > /* pageid fields */ > clrrwi r3,r3,10 /* Mask off the effective page number */ > - ori r3,r3,PPC44x_TLB_VALID | PPC44x_TLB_256M > + ori r3,r3,PPC44x_TLB_VALID | PPC44x_TLB_PIN_SIZE > > /* xlat fields */ > clrrwi r4,r4,10 /* Mask off the real page number */ > Index: linux-2.6.38.1/arch/powerpc/mm/44x_mmu.c > =================================================================== > --- linux-2.6.38.1.orig/arch/powerpc/mm/44x_mmu.c > +++ linux-2.6.38.1/arch/powerpc/mm/44x_mmu.c > @@ -84,7 +84,7 @@ static void __init ppc44x_pin_tlb(unsign > : "r" (PPC44x_TLB_SW | PPC44x_TLB_SR | PPC44x_TLB_SX | PPC44x_TLB_G), > #endif > "r" (phys), > - "r" (virt | PPC44x_TLB_VALID | PPC44x_TLB_256M), > + "r" (virt | PPC44x_TLB_VALID | PPC44x_TLB_PIN_SIZE), > "r" (entry), > "i" (PPC44x_TLB_PAGEID), > "i" (PPC44x_TLB_XLAT), > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev