* Re: [PATCHv7] rtc: Add support for Intersil ISL12057 I2C RTC chip
[not found] <72207bc152a06638f0e0e21a6e00d4c2054a1a71.1387489507.git.arno@natisbad.org>
@ 2013-12-19 22:07 ` Andrew Morton
2013-12-19 22:22 ` Arnaud Ebalard
0 siblings, 1 reply; 2+ messages in thread
From: Andrew Morton @ 2013-12-19 22:07 UTC (permalink / raw)
To: Arnaud Ebalard
Cc: Jason Cooper, Mark Rutland, Alessandro Zummo, Peter Huewe,
Linus Walleij, Thierry Reding, Mark Brown, Guenter Roeck,
Rob Herring, Pawel Moll, Stephen Warren, Ian Campbell,
Grant Likely, devicetree, linux-doc, Rob Landley, rtc-linux,
Jason Gunthorpe, Kumar Gala, linux-arm-kernel, linux-kernel
On Thu, 19 Dec 2013 22:53:16 +0100 Arnaud Ebalard <arno@natisbad.org> wrote:
> +static int isl12057_i2c_validate_chip(struct regmap *regmap)
> +{
> + u8 regs[ISL12057_MEM_MAP_LEN];
> + u8 mask[ISL12057_MEM_MAP_LEN] = { 0x80, 0x80, 0x80, 0xf8,
> + 0xc0, 0x60, 0x00, 0x00,
> + 0x00, 0x00, 0x00, 0x00,
> + 0x00, 0x00, 0x60, 0x7c };
> + int ret, i;
> +
> + ret = regmap_bulk_read(regmap, 0, regs, ISL12057_MEM_MAP_LEN);
> + if (ret)
> + return ret;
> +
> + for (i = 0; i < ISL12057_MEM_MAP_LEN; ++i) {
> + if (regs[i] & mask[i]) /* check if bits are cleared */
> + return -ENODEV;
> + }
> +
> + return 0;
> +}
When I build this for x86_64, mask[] is assembled on-stack at runtime:
leaq -48(%rbp), %r14 #, tmp130
xorl %esi, %esi #
movl $16, %ecx #,
movq %rax, %rdi # regmap,
incq .LPBX1+552(%rip) # *.LPBX1
movb $-128, -64(%rbp) #, mask
movq %r14, %rdx # tmp130,
movb $-128, -63(%rbp) #, mask
movb $-128, -62(%rbp) #, mask
movb $-8, -61(%rbp) #, mask
movb $-64, -60(%rbp) #, mask
movb $96, -59(%rbp) #, mask
movb $0, -58(%rbp) #, mask
movb $0, -57(%rbp) #, mask
movb $0, -56(%rbp) #, mask
movb $0, -55(%rbp) #, mask
movb $0, -54(%rbp) #, mask
movb $0, -53(%rbp) #, mask
movb $0, -52(%rbp) #, mask
movb $0, -51(%rbp) #, mask
movb $96, -50(%rbp) #, mask
movb $124, -49(%rbp) #, mask
call regmap_bulk_read #
If we make `mask' static const, that all gets done at compile time instead:
leaq -48(%rbp), %r14 #, tmp134
xorl %esi, %esi #
movl $16, %ecx #,
movq %rax, %rdi # regmap,
incq .LPBX1+552(%rip) # *.LPBX1
movq %r14, %rdx # tmp134,
call regmap_bulk_read #
much nicer.
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCHv7] rtc: Add support for Intersil ISL12057 I2C RTC chip
2013-12-19 22:07 ` [PATCHv7] rtc: Add support for Intersil ISL12057 I2C RTC chip Andrew Morton
@ 2013-12-19 22:22 ` Arnaud Ebalard
0 siblings, 0 replies; 2+ messages in thread
From: Arnaud Ebalard @ 2013-12-19 22:22 UTC (permalink / raw)
To: Andrew Morton
Cc: Mark Rutland, Alessandro Zummo, Jason Cooper, Pawel Moll,
Stephen Warren, rtc-linux, Linus Walleij, Ian Campbell, linux-doc,
linux-kernel, Rob Herring, Jason Gunthorpe, devicetree,
Mark Brown, linux-arm-kernel, Rob Landley, Kumar Gala,
Grant Likely, Peter Huewe, Thierry Reding, Guenter Roeck
Hi Andrew,
Andrew Morton <akpm@linux-foundation.org> writes:
> On Thu, 19 Dec 2013 22:53:16 +0100 Arnaud Ebalard <arno@natisbad.org> wrote:
>
>> +static int isl12057_i2c_validate_chip(struct regmap *regmap)
>> +{
>> + u8 regs[ISL12057_MEM_MAP_LEN];
>> + u8 mask[ISL12057_MEM_MAP_LEN] = { 0x80, 0x80, 0x80, 0xf8,
>> + 0xc0, 0x60, 0x00, 0x00,
>> + 0x00, 0x00, 0x00, 0x00,
>> + 0x00, 0x00, 0x60, 0x7c };
>> + int ret, i;
>> +
>> + ret = regmap_bulk_read(regmap, 0, regs, ISL12057_MEM_MAP_LEN);
>> + if (ret)
>> + return ret;
>> +
>> + for (i = 0; i < ISL12057_MEM_MAP_LEN; ++i) {
>> + if (regs[i] & mask[i]) /* check if bits are cleared */
>> + return -ENODEV;
>> + }
>> +
>> + return 0;
>> +}
>
> When I build this for x86_64, mask[] is assembled on-stack at runtime:
>
> leaq -48(%rbp), %r14 #, tmp130
> xorl %esi, %esi #
> movl $16, %ecx #,
> movq %rax, %rdi # regmap,
> incq .LPBX1+552(%rip) # *.LPBX1
> movb $-128, -64(%rbp) #, mask
> movq %r14, %rdx # tmp130,
> movb $-128, -63(%rbp) #, mask
> movb $-128, -62(%rbp) #, mask
> movb $-8, -61(%rbp) #, mask
> movb $-64, -60(%rbp) #, mask
> movb $96, -59(%rbp) #, mask
> movb $0, -58(%rbp) #, mask
> movb $0, -57(%rbp) #, mask
> movb $0, -56(%rbp) #, mask
> movb $0, -55(%rbp) #, mask
> movb $0, -54(%rbp) #, mask
> movb $0, -53(%rbp) #, mask
> movb $0, -52(%rbp) #, mask
> movb $0, -51(%rbp) #, mask
> movb $96, -50(%rbp) #, mask
> movb $124, -49(%rbp) #, mask
> call regmap_bulk_read #
>
> If we make `mask' static const, that all gets done at compile time instead:
>
> leaq -48(%rbp), %r14 #, tmp134
> xorl %esi, %esi #
> movl $16, %ecx #,
> movq %rax, %rdi # regmap,
> incq .LPBX1+552(%rip) # *.LPBX1
> movq %r14, %rdx # tmp134,
> call regmap_bulk_read #
>
> much nicer.
Damned. That's a good argument for a v8 ;-) Give me some minutes to
assemble one.
Cheers,
a+
^ permalink raw reply [flat|nested] 2+ messages in thread
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2013-12-19 22:07 ` [PATCHv7] rtc: Add support for Intersil ISL12057 I2C RTC chip Andrew Morton
2013-12-19 22:22 ` Arnaud Ebalard
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