Messages in this thread | | | Subject | Re: [PATCH 2/2] mtd: spi-nor: add driver for STM32 quad spi flash controller | From | Ludovic BARRE <> | Date | Wed, 29 Mar 2017 18:38:56 +0200 |
| |
On 03/29/2017 03:57 PM, Marek Vasut wrote: > On 03/29/2017 03:35 PM, Ludovic BARRE wrote: > > [...] > >>>>>> + writel_relaxed(CR_PRESC(presc) | CR_FTHRES(3) | CR_TCEN | >>>>>> CR_SSHIFT >>>>>> + | CR_EN, qspi->io_base + QUADSPI_CR); >>>>>> + >>>>>> + /* a minimum fsize must be set to sent the command id */ >>>>>> + flash->fsize = 25; >>>>> I don't understand why this is needed and the comment doesn't make >>>>> sense. Please fix. >>>> fsize field defines the size of external memory. >>> What external memory ? Unclear >> oops, fsize field defined the size of "flash memory" in stm32 qspi >> controller. > Errr, now I am totally lost :) Is that some internal SPI NOR ? Shouldn't > the size be coming from DT or something ? > >> Number of bytes in Flash memory = 2 ^[FSIZE+1]. >> To sent a nor cmd this field must be set (hardware issue), >> but before "spi_nor_scan" the size of flash nor is not know. >> So I set a temporary value (workaround). > Is it needed before the scan ? yes it's needed before scan (fix a "stm32 qspi controller" issue)
sorry, I try to reformulate:
The nor flash (external component like micron n25q128a13 or spansion s25fl512s ...) is connected to stm32 by classic spi-nor interface cs, clock and 1/2/4 IO lines.
the stm32 microprocessor has a dedicated controller to manage spi-nor interface, it's stm32 qspi.
In stm32 qspi controller there is a register with fsize field which define the size of nor flash (n25q128a13 or s25fl512s...).
fsize can't be null, else the stm32 qspi controller doesn't send spi-nor command. it's "stm32 qspi controller" issue.
Before the "spi_nor_scan" the size of nor flash (n25q128a13 or s25fl512s...) is not know. So we set a temporary value just to discover the nor flash with "spi_nor_scan". After we can set the right value (mtd->size) in fsize. >> After "spi_nor_scan" the fsize is overwritten by the right value >> flash->fsize = __fls(mtd->size) - 1; >>>> Normaly, this field is used only for memory map mode, >>>> but in fact is check in indirect mode. >>>> So while flash scan "spi_nor_scan": >>>> -I can't let 0. >>>> -I not know yet the size of flash. >>>> So I fix a temporary value >>>> >>>> I will update my comment >>> Please do, also please consider that I'm reading the comment and I >>> barely have any clue about this hardware , so make sure I can >>> understand it. >>> >>>>>> + ret = spi_nor_scan(&flash->nor, NULL, flash_read); >>>>>> + if (ret) { >>>>>> + dev_err(qspi->dev, "device scan failed\n"); >>>>>> + return ret; >>>>>> + } >>>>>> + >>>>>> + flash->fsize = __fls(mtd->size) - 1; >>>>>> + >>>>>> + writel_relaxed(DCR_CSHT(1), qspi->io_base + QUADSPI_DCR); >>>>>> + >>>>>> + ret = mtd_device_register(mtd, NULL, 0); >>>>>> + if (ret) { >>>>>> + dev_err(qspi->dev, "mtd device parse failed\n"); >>>>>> + return ret; >>>>>> + } >>>>>> + >>>>>> + dev_dbg(qspi->dev, "read mm:%s cs:%d bus:%d\n", >>>>>> + qspi->read_mode == CCR_FMODE_MM ? "yes" : "no", cs_num, >>>>>> width); >>>>>> + >>>>>> + return 0; >>>>>> +} >>>>> [...] >>>>> >
| |