Messages in this thread |  | | Date | Thu, 28 Nov 2013 09:07:15 +0000 | From | Angus Clark <> | Subject | Re: [PATCH 00/23] mtd: st_spi_fsm: Add new device |
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Hi Huang Shijie,
On 11/28/2013 03:34 AM, Huang Shijie wrote: > 于 2013年11月27日 19:52, Lee Jones 写道: >> However, as we send entire 'message sequences' to the FSM Controller >> as opposed to merely OPCODEs we would have to extract the OPCODE from >> flash->command[0] and call our own functions to craft the correct >> 'message sequence' for the task. For this reason we rejected the idea >> and went with a stand-alone driver. >> > could you send me the datasheet of your spi nor controller? > I can change my code if it really not good enough.
I will reply to the "mtd: spi-nor" thread regarding the proposed framework, but a couple of answers to your specific questions below.
> > we can store the opcode to a field, such as spi_nor_write_op. >> The framework which Huang is proposing suffers from the same issues. >> Only providing read(), write(), read_reg() and write_reg() doesn't >> work for our use-case, as we'd have to decode the flash->command[0] and >> invoke our own internal routines as before. >> >> The only framework with would work for us would consist almost all >> of the important functions such as; read(), write(), erase(), >> wait_busy(), read_jedec(), read_status_reg(), write_status_reg(), >> read_control_reg(), write_control_reg(), etc. However, this approach >> > read_jedec() can be replaced by read_reg(0x9f); > > read_status() can be replaced by read_reg(0x5); > > .... > > write_control_reg() can be replaced by write_reg(xx).
Unfortunately the H/W Controller in question comes with a few restrictions. One restriction is that data must be read in multiples of 4 bytes. As such, it would not be able to honour a call of "flash->read_reg(flash, OPCODE_RDID, id, 5);"
Of course, if the H/W driver knows that we are issuing a read_jedec() operation, then it can make the assumption that over-reading is benign, and we can instead read 8 bytes of data from the Flash device, and return 5 to the caller. However, without knowing what operation is being requested, no such assumption can be made.
> Please correct me if i am wrong. > > IMHO, the current four hooks for spi-nor{} can do all the things. > > read/write/read_reg/write_reg.
As it stands, the spi-nor framework cannot support the requirements of the st_spi_fsm controller. I will go into further details on the "mtd: spi-nor" thread.
Cheers,
Angus
-- ------------------------------------- Angus Clark ST Microelectronics (R&D) Ltd. 1000 Aztec West, Bristol, BS32 4SQ email: angus.clark@st.com tel: +44 (0) 1454 462389 st-tina: 065 2389 ------------------------------------- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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