Re: [PATCH RFC v4 1/1] scsi: ufs: Fix ufs power down/on specs violation

On 22/12/20 3:49 pm, Ziqi Chen wrote:

As per specs, e.g, JESD220E chapter 7.2, while powering
off/on the ufs device, RST_N signal and REF_CLK signal
should be between VSS(Ground) and VCCQ/VCCQ2.

To flexibly control device reset line, refactor the function
ufschd_vops_device_reset(sturct ufs_hba *hba) to ufshcd_
vops_device_reset(sturct ufs_hba *hba, bool asserted). The
new parameter "bool asserted" is used to separate device reset
line pulling down from pulling up.

This patch assumes the power is controlled by voltage regulators, but for us
it is controlled by firmware (ACPI), so it is not correct to change RST_n
for all host controllers as you are doing.

Also we might need to use a firmware interface for device reset, in which
case the 'asserted' value doe not make sense.

Can we leave the device reset callback alone, and instead introduce a new
variant operation for setting RST_n to match voltage regulator power changes?

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