| Message ID | cover.1642348712.git.mirq-linux@rere.qmqm.pl |
|---|---|
| Headers | show |
| Series | i2c: tegra: allow compiling out support for Tegra's special constrollers | expand |
16.01.2022 19:02, Michał Mirosław пишет: > To patches that, combined, reduce I2C driver's code by ~2kB and a bit > from runtime overhead for non-Tegra20 or non-Tegra210 builds. > > Michał Mirosław (2): > i2c: tegra: allow DVC support to be compiled out > i2c: tegra: allow VI support to be compiled out > > drivers/i2c/busses/Kconfig | 16 ++++++++++++++++ > drivers/i2c/busses/i2c-tegra.c | 35 +++++++++++++++++++++------------- > 2 files changed, 38 insertions(+), 13 deletions(-) > 2KB is a too small difference to justify the ifdefs and Kconfig entries, IMO.
On Sun, Jan 16, 2022 at 08:54:08PM +0300, Dmitry Osipenko wrote: > 16.01.2022 19:02, Michał Mirosław пишет: > > To patches that, combined, reduce I2C driver's code by ~2kB and a bit > > from runtime overhead for non-Tegra20 or non-Tegra210 builds. > > > > Michał Mirosław (2): > > i2c: tegra: allow DVC support to be compiled out > > i2c: tegra: allow VI support to be compiled out > > > > drivers/i2c/busses/Kconfig | 16 ++++++++++++++++ > > drivers/i2c/busses/i2c-tegra.c | 35 +++++++++++++++++++++------------- > > 2 files changed, 38 insertions(+), 13 deletions(-) > > > > 2KB is a too small difference to justify the ifdefs and Kconfig entries, > IMO. Maybe I should have mentioned that it's ~20%? With my "embedded" hat on: I think it might be small, but sometimes it is the difference between bootable kernel or one too big. Best Regards Michał Mirosław
16.01.2022 21:03, Michał Mirosław пишет: > On Sun, Jan 16, 2022 at 08:54:08PM +0300, Dmitry Osipenko wrote: >> 16.01.2022 19:02, Michał Mirosław пишет: >>> To patches that, combined, reduce I2C driver's code by ~2kB and a bit >>> from runtime overhead for non-Tegra20 or non-Tegra210 builds. >>> >>> Michał Mirosław (2): >>> i2c: tegra: allow DVC support to be compiled out >>> i2c: tegra: allow VI support to be compiled out >>> >>> drivers/i2c/busses/Kconfig | 16 ++++++++++++++++ >>> drivers/i2c/busses/i2c-tegra.c | 35 +++++++++++++++++++++------------- >>> 2 files changed, 38 insertions(+), 13 deletions(-) >>> >> >> 2KB is a too small difference to justify the ifdefs and Kconfig entries, >> IMO. > > Maybe I should have mentioned that it's ~20%? With my "embedded" hat on: > I think it might be small, but sometimes it is the difference between > bootable kernel or one too big. 10KB is a small size too. I'm very doubtful that such changes make any real difference in practice. Much more practical should be to modularize more kernel code. You should be able to squeeze zImage down to 3MB without any code changes by toggling more kernel config options to =m. Try to use grate_defconfig [1] for the base, that is what postmarketOS kernel build uses. [1] https://github.com/grate-driver/linux/blob/master/arch/arm/configs/grate_defconfig
On Sun, Jan 16, 2022 at 09:34:42PM +0300, Dmitry Osipenko wrote: > 16.01.2022 21:03, Michał Mirosław пишет: > > On Sun, Jan 16, 2022 at 08:54:08PM +0300, Dmitry Osipenko wrote: > >> 16.01.2022 19:02, Michał Mirosław пишет: > >>> To patches that, combined, reduce I2C driver's code by ~2kB and a bit > >>> from runtime overhead for non-Tegra20 or non-Tegra210 builds. > >>> > >>> Michał Mirosław (2): > >>> i2c: tegra: allow DVC support to be compiled out > >>> i2c: tegra: allow VI support to be compiled out > >>> > >>> drivers/i2c/busses/Kconfig | 16 ++++++++++++++++ > >>> drivers/i2c/busses/i2c-tegra.c | 35 +++++++++++++++++++++------------- > >>> 2 files changed, 38 insertions(+), 13 deletions(-) > >>> > >> > >> 2KB is a too small difference to justify the ifdefs and Kconfig entries, > >> IMO. > > > > Maybe I should have mentioned that it's ~20%? With my "embedded" hat on: > > I think it might be small, but sometimes it is the difference between > > bootable kernel or one too big. > > 10KB is a small size too. I'm very doubtful that such changes make any > real difference in practice. > > Much more practical should be to modularize more kernel code. You should > be able to squeeze zImage down to 3MB without any code changes by > toggling more kernel config options to =m. Try to use grate_defconfig > [1] for the base, that is what postmarketOS kernel build uses. For normal system this solution is workable. But for recovery, where you have to fit kernel+initrd in whatever small partition is provided (like eg. in Transformers 8MiB), it becomes a problem from time to time. (In this case, modules make it worse due to additional overhead in kernel and userspace). Best Regards Michał Mirosław
17.01.2022 00:39, Michał Mirosław пишет: > On Sun, Jan 16, 2022 at 09:34:42PM +0300, Dmitry Osipenko wrote: >> 16.01.2022 21:03, Michał Mirosław пишет: >>> On Sun, Jan 16, 2022 at 08:54:08PM +0300, Dmitry Osipenko wrote: >>>> 16.01.2022 19:02, Michał Mirosław пишет: >>>>> To patches that, combined, reduce I2C driver's code by ~2kB and a bit >>>>> from runtime overhead for non-Tegra20 or non-Tegra210 builds. >>>>> >>>>> Michał Mirosław (2): >>>>> i2c: tegra: allow DVC support to be compiled out >>>>> i2c: tegra: allow VI support to be compiled out >>>>> >>>>> drivers/i2c/busses/Kconfig | 16 ++++++++++++++++ >>>>> drivers/i2c/busses/i2c-tegra.c | 35 +++++++++++++++++++++------------- >>>>> 2 files changed, 38 insertions(+), 13 deletions(-) >>>>> >>>> >>>> 2KB is a too small difference to justify the ifdefs and Kconfig entries, >>>> IMO. >>> >>> Maybe I should have mentioned that it's ~20%? With my "embedded" hat on: >>> I think it might be small, but sometimes it is the difference between >>> bootable kernel or one too big. >> >> 10KB is a small size too. I'm very doubtful that such changes make any >> real difference in practice. >> >> Much more practical should be to modularize more kernel code. You should >> be able to squeeze zImage down to 3MB without any code changes by >> toggling more kernel config options to =m. Try to use grate_defconfig >> [1] for the base, that is what postmarketOS kernel build uses. > > For normal system this solution is workable. But for recovery, where you > have to fit kernel+initrd in whatever small partition is provided (like > eg. in Transformers 8MiB), it becomes a problem from time to time. > (In this case, modules make it worse due to additional overhead in > kernel and userspace). My point is that 2KB very likely won't change anything for you. I'd suggest to take a look at a more "fat" drivers, like DRM/host1x for example. I suppose it should be possible to save at least couple hundreds KB by trimming those fat drivers.
On Mon, Jan 17, 2022 at 06:37:12PM +0300, Dmitry Osipenko wrote: > 17.01.2022 00:39, Michał Mirosław пишет: > > On Sun, Jan 16, 2022 at 09:34:42PM +0300, Dmitry Osipenko wrote: > >> 16.01.2022 21:03, Michał Mirosław пишет: > >>> On Sun, Jan 16, 2022 at 08:54:08PM +0300, Dmitry Osipenko wrote: > >>>> 16.01.2022 19:02, Michał Mirosław пишет: > >>>>> To patches that, combined, reduce I2C driver's code by ~2kB and a bit > >>>>> from runtime overhead for non-Tegra20 or non-Tegra210 builds. > >>>>> > >>>>> Michał Mirosław (2): > >>>>> i2c: tegra: allow DVC support to be compiled out > >>>>> i2c: tegra: allow VI support to be compiled out > >>>>> > >>>>> drivers/i2c/busses/Kconfig | 16 ++++++++++++++++ > >>>>> drivers/i2c/busses/i2c-tegra.c | 35 +++++++++++++++++++++------------- > >>>>> 2 files changed, 38 insertions(+), 13 deletions(-) > >>>>> > >>>> > >>>> 2KB is a too small difference to justify the ifdefs and Kconfig entries, > >>>> IMO. > >>> > >>> Maybe I should have mentioned that it's ~20%? With my "embedded" hat on: > >>> I think it might be small, but sometimes it is the difference between > >>> bootable kernel or one too big. > >> > >> 10KB is a small size too. I'm very doubtful that such changes make any > >> real difference in practice. > >> > >> Much more practical should be to modularize more kernel code. You should > >> be able to squeeze zImage down to 3MB without any code changes by > >> toggling more kernel config options to =m. Try to use grate_defconfig > >> [1] for the base, that is what postmarketOS kernel build uses. > > > > For normal system this solution is workable. But for recovery, where you > > have to fit kernel+initrd in whatever small partition is provided (like > > eg. in Transformers 8MiB), it becomes a problem from time to time. > > (In this case, modules make it worse due to additional overhead in > > kernel and userspace). > > My point is that 2KB very likely won't change anything for you. I'd > suggest to take a look at a more "fat" drivers, like DRM/host1x for > example. I suppose it should be possible to save at least couple > hundreds KB by trimming those fat drivers. No doubt we can find more code to trim. :-) This one was cheap and easy, though. BTW, I worked around host1x size by using simpledrmfb instead, so I'm not sure there will be much benefit to digging there. Best Regards Michał Mirosław