Hi Cyrille, Thank you for so detailed explanation. I'll check nor->addr_width in both mt8173_nor_read() and mt8173_nor_write(). Best regards, Guochun On Fri, 2017-03-31 at 10:56 +0200, Cyrille Pitchen wrote: > Le 31/03/2017 à 04:26, Guochun Mao a écrit : > > Hi Cyrille, Marek, > > > > Thanks for your suggestions. > > > > On Thu, 2017-03-30 at 19:40 +0200, Cyrille Pitchen wrote: > >> Hi Guochun, > >> > >> Le 30/03/2017 à 10:23, Guochun Mao a écrit : > >>> when nor's size larger than 16MByte, nor and controller should > >>> enter 4Byte mode simultaneously. > >>> > >>> Signed-off-by: Guochun Mao <guochun.mao@xxxxxxxxxxxx> > >>> --- > >>> drivers/mtd/spi-nor/mtk-quadspi.c | 7 +++++++ > >>> 1 file changed, 7 insertions(+) > >>> > >>> diff --git a/drivers/mtd/spi-nor/mtk-quadspi.c b/drivers/mtd/spi-nor/mtk-quadspi.c > >>> index e661877..05cd8a8 100644 > >>> --- a/drivers/mtd/spi-nor/mtk-quadspi.c > >>> +++ b/drivers/mtd/spi-nor/mtk-quadspi.c > >>> @@ -369,6 +369,13 @@ static int mt8173_nor_write_reg(struct spi_nor *nor, u8 opcode, u8 *buf, > >>> /* We only handle 1 byte */ > >>> ret = mt8173_nor_wr_sr(mt8173_nor, *buf); > >>> break; > >>> + case SPINOR_OP_EN4B: > >>> + /* Set nor controller to 4-byte address mode, > >>> + * and simultaneously set nor flash. > >>> + * This case should cooperate with default operation. > >>> + */ > >>> + writeb(readb(mt8173_nor->base + MTK_NOR_DUAL_REG) | 0x10, > >>> + mt8173_nor->base + MTK_NOR_DUAL_REG); > >> > >> This is not good: you should check in both mt8173_nor_read() and > >> mt8173_nor_write() whether nor->addr_width is either 3 or 4. > >> > >> from include/linux/mtd/spi-nor.h: > >> * @addr_width: number of address bytes > >> > >> Besides SPI commands using an op code from 4-byte address instruction > >> set always carry a 4-byte address. They can be used directly, without > >> sending the SPINOR_OP_EN4B before. So you cannot assume that addresses > >> will be 4-byte long only if your SPI controller driver has seen a > >> SPINOR_OP_EN4B command before. This assumption is wrong. > > Nor->addr_width is assigned in spi_nor_scan in spi-nor.c, and it's not > > modified in later process. > > Does it means that we will not switch nor between 3Byte address and > > 4Byte? > > So, is it better to check nor->addr_width when do nor initialization? > > > > Currently yes, nor->addr_width, nor->read_opcode, nor->read_dummy, and > nor->program_opcode are set once for all in spi_nor_scan(). > > However, nor->read() is likely to be called soon from spi_nor_scan() > with values of nor->addr_width, nor->read_opcode and nor->read_dummy > different from those selected when exiting spi_nor_scan(). > > So nor->read() / mt8173_nor_read should check nor->addr_width, > nor->read_opcode and nor->read_dummy at each call. > > More precisely, I plan to use nor->read() from spi_nor_scan() to read > SFDP (Serial Flash Discoverable Parameters) data. > > Whatever op code, numbers of address bytes and dummy cycles used for > (Fast) Read commands, the Read SFDP command uses fixed settings > standardized for all manufacturers and all memory parts: > - op code: 5Ah > - number of bytes for the address: 3 (even for memory > 128Mbits) > - number of dummy clock cycles: 8 clocks > > https://patchwork.ozlabs.org/patch/742380/ > > Please have a look at the spi_nor_read_sfdp(). > > spi_nor_read_sfdp() is likely to be called from and only from > spi_nor_scan(). > > Best regards, > > Cyrille > > >> > >> SPI controller driver should never check SPINOR_OP_* op codes like this. > > I agree that SPI controller driver should not check SPINOR_OP_* op codes > > like what I do. > > I will correct it next version. > > > > Best Regards, > > Guochun > >> > >> Then, testing SPINOR_OP_RDSR from mt8173_nor_read_reg() or > >> SPINOR_OP_WRSR from mt8173_nor_write_reg() is not a good practice too: > >> op codes may change depending on the memory manufacturer. So testing op > >> code values like you do can work with some memories but maybe not all. > >> > >> Finally, don't use 0x10, please define a macro instead. > >> > >> Best regards, > >> > >> Cyrille > >> > >>> default: > >>> ret = mt8173_nor_do_tx_rx(mt8173_nor, opcode, buf, len, NULL, 0); > >>> if (ret) > >>> > >> > > > > > > > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
