On 4/13/2016 8:15 AM, Mark Brown wrote:
>+static void st_get_satinize_powerup_voltage(struct st_vsense *vsense) >+{ >+ void __iomem *ioaddr = vsense->ioaddr; >+ u32 value = readl_relaxed(ioaddr); >+ >+ dev_dbg(vsense->dev, "Initial start-up value: (0x%08x)\n", value); >+ >+ /* Sanitize voltage values forcing what is provided from start-up */ >+ if (value & TOP_VSENSE_CONFIG_LATCHED_PSW_EMMC) >+ value |= TOP_VSENSE_CONFIG_REG_PSW_EMMC; >+ else >+ value &= ~TOP_VSENSE_CONFIG_REG_PSW_EMMC; >+ >+ if (value & TOP_VSENSE_CONFIG_LATCHED_PSW_NAND) >+ value |= TOP_VSENSE_CONFIG_REG_PSW_NAND; >+ else >+ value &= ~TOP_VSENSE_CONFIG_REG_PSW_NAND; >+ >+ if (value & TOP_VSENSE_CONFIG_LATCHED_PSW_SPI) >+ value |= TOP_VSENSE_CONFIG_REG_PSW_SPI; >+ else >+ value &= ~TOP_VSENSE_CONFIG_REG_PSW_SPI;This looks like a very complicated way of writing value &= TOP_VSENSE_CONFIG_LATCHED_PSW_SPI | TOP_VSENSE_CONFIG_LATCHED_PSW_NAND | TOP_VSENSE_CONFIG_REG_PSW_EMMC or am I missing something? Why do we need to do this anyway, it's very surprsing?
This functions is to sanitize the vsense voltages when the regulator is probed and in some circumstances the reset value of this register does not reflect the hw status/config. For example, by default, after the reset, the bit 0 is set so the EMMC, inside the flash subsystem, is supposed to operate at 3v3. But the latched bit 24 can be 0 on a platform where it is actually set at 1v8. So the bit 0 must be reset to keep this coherent and to allow MMC framework to properly setup the Vdd when the framework starts. Hoping this can help. Regards peppe -- 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
