Messages in this thread |  | | Date | Sun, 27 Feb 2022 22:27:52 +0100 | Subject | Re: [PATCH 08/10] spi: aspeed: Calibrate read timings | From | Cédric Le Goater <> |
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On 2/25/22 10:18, Pratyush Yadav wrote: > On 14/02/22 10:42AM, Cédric Le Goater wrote: >> To accommodate the different response time of SPI transfers on different >> boards and different SPI NOR devices, the Aspeed controllers provide a >> set of Read Timing Compensation registers to tune the timing delays >> depending on the frequency being used. The AST2600 SoC has one of >> these registers per device. On the AST2500 and AST2400 SoCs, the >> timing register is shared by all devices which is a bit problematic to >> get good results other than for one device. >> >> The algorithm first reads a golden buffer at low speed and then performs >> reads with different clocks and delay cycle settings to find a breaking >> point. This selects a default good frequency for the CEx control register. >> The current settings are bit optimistic as we pick the first delay giving >> good results. A safer approach would be to determine an interval and >> choose the middle value. >> >> Due to the lack of API, calibration is performed when the direct mapping >> for reads is created. > > The dirmap_create mapping says nothing about _when_ it should be called. > So there is no guarantee that it will only be called after the flash is > fully initialized.
spi_nor_create_read_dirmap() is called after spi_nor_scan() in spi_nor_probe(). Since a spi_mem_dirmap_info descriptor is created using the nor fields :
struct spi_mem_dirmap_info info = { .op_tmpl = SPI_MEM_OP(SPI_MEM_OP_CMD(nor->read_opcode, 0), SPI_MEM_OP_ADDR(nor->addr_width, 0, 0), SPI_MEM_OP_DUMMY(nor->read_dummy, 0), SPI_MEM_OP_DATA_IN(0, NULL, 0)), .offset = 0, .length = nor->params->size, }; struct spi_mem_op *op = &info.op_tmpl;
the spi-mem framework makes the assumption that the nor object is initialized.
> I suggest you either make this a requirement of the API,
how ?
Thanks,
C.
> or create a new API that guarantees it will only be called after > the flash is initialized, like [0]. > > [0] https://patchwork.ozlabs.org/project/linux-mtd/patch/20210311191216.7363-2-p.yadav@ti.com/ > >> >> Cc: Pratyush Yadav <p.yadav@ti.com> >> Signed-off-by: Cédric Le Goater <clg@kaod.org> >> --- >
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