Messages in this thread | | | Date | Fri, 15 May 2020 12:25:08 +0530 | From | Pratyush Yadav <> | Subject | Re: [PATCH v2 0/5] mtd: spi-nor: Add support for Octal 8D-8D-8D mode |
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Hi Mason,
On 15/05/20 10:26AM, masonccyang@mxic.com.tw wrote: > > Hi Pratyush, > > > > > > I can't apply your patches to enable xSPI Octal mode for > > > > > mx25uw51245g because your patches set up Octal protocol first and > > > > > then using Octal protocol to write Configuration Register 2(CFG > > > > > Reg2). I think driver > > > > > should write CFG Reg2 in SPI 1-1-1 mode (power on state) and make > sure > > > > > write CFG Reg 2 is success and then setup Octa protocol in the > last. > > > > > > > > Register writes should work in 1S mode, because nor->reg_proto is > only > > > > set _after_ 8D mode is enabled (see spi_nor_octal_dtr_enable()). In > > > > fact, both patch 15 and 16 in my series use register writes in 1S > mode. > > > > > > but I didn't see driver roll back "nor->read/write_proto = 1" > > > if xxx->octal_dtr_enable() return failed! > > > > I copied what spi_nor_quad_enable() did, and made failure fatal. So if > > xxx->octal_dtr_enable() fails, the probe would fail and the flash would > > be unusable. You can try your hand at a fallback system where you try > > IMHO, it's not a good for system booting from SPI-NOR, > driver should still keep system alive in SPI 1-1-1 mode in case of > enable Octal/Quad failed.
I agree.
> Therefore, my patches is to setup nor->read/write_proto = 8 in case > driver enable Octal mode is success. And to enable Octal mode in > spi_nor_late_init_params()rather than as spi_nor_quad_enable()did.
Like I mentioned before, spi_nor_late_init_params() is called _before_ we call spi_nor_spimem_adjust_hwcaps(). That call is needed to make sure the controller also supports octal mode operations. Otherwise, you'd end up enabling octal mode on a controller that doesn't support it with no way of going back now.
But we can still have a fallback mechanism even in spi_nor_init() that would switch to a "less preferred" mode (like 1-1-1 mode) if "more preferred" ones like octal or quad fail.
That said, I think it would be a good idea to not keep tacking features on this series. This makes it harder for reviewers because now they are trying to shoot a moving target. Let basic 8D support stabilize and get merged in, and then a fallback system can be submitted as a separate patch series.
-- Regards, Pratyush Yadav
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