Commit 6c171994 authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt
Browse files

powerpc/of: Remove useless register save/restore when calling OF back 



enter_prom() used to save and restore registers such as CTR, XER etc..
which are volatile, or SRR0,1... which we don't care about. This
removes a bunch of useless code and while at it turns an mtmsrd into
an MTMSRD macro which will be useful to Book3E.

Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 7d60b02c

arch/powerpc/kernel/entry_64.S

+6 −32
Original line number Diff line number Diff line
@@ -823,30 +823,17 @@ _GLOBAL(enter_prom) 
	 * of all registers that it saves.  We therefore save those registers

	 * PROM might touch to the stack.  (r0, r3-r13 are caller saved)

   	 */

	SAVE_8GPRS(2, r1)

	SAVE_GPR(2, r1)

	SAVE_GPR(13, r1)

	SAVE_8GPRS(14, r1)

	SAVE_10GPRS(22, r1)

	mfcr	r4

	std	r4,_CCR(r1)

	mfctr	r5

	std	r5,_CTR(r1)

	mfspr	r6,SPRN_XER

	std	r6,_XER(r1)

	mfdar	r7

	std	r7,_DAR(r1)

	mfdsisr	r8

	std	r8,_DSISR(r1)

	mfsrr0	r9

	std	r9,_SRR0(r1)

	mfsrr1	r10

	std	r10,_SRR1(r1)

	mfcr	r10

	mfmsr	r11

	std	r10,_CCR(r1)

	std	r11,_MSR(r1)



	/* Get the PROM entrypoint */

	ld	r0,GPR4(r1)

	mtlr	r0

	mtlr	r4



	/* Switch MSR to 32 bits mode

	 */
@@ -860,8 +847,7 @@ _GLOBAL(enter_prom) 
        mtmsrd  r11

        isync



	/* Restore arguments & enter PROM here... */

	ld	r3,GPR3(r1)

	/* Enter PROM here... */

	blrl



	/* Just make sure that r1 top 32 bits didn't get
@@ -871,7 +857,7 @@ _GLOBAL(enter_prom) 


	/* Restore the MSR (back to 64 bits) */

	ld	r0,_MSR(r1)

	mtmsrd	r0

	MTMSRD(r0)

        isync



	/* Restore other registers */
@@ -881,18 +867,6 @@ _GLOBAL(enter_prom) 
	REST_10GPRS(22, r1)

	ld	r4,_CCR(r1)

	mtcr	r4

	ld	r5,_CTR(r1)

	mtctr	r5

	ld	r6,_XER(r1)

	mtspr	SPRN_XER,r6

	ld	r7,_DAR(r1)

	mtdar	r7

	ld	r8,_DSISR(r1)

	mtdsisr	r8

	ld	r9,_SRR0(r1)

	mtsrr0	r9

	ld	r10,_SRR1(r1)

	mtsrr1	r10

	

        addi	r1,r1,PROM_FRAME_SIZE

	ld	r0,16(r1)

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