Hi Mani,
On 11/8/2023 1:23 PM, Manivannan Sadhasivam wrote:
On Mon, Nov 06, 2023 at 08:46:09PM -0800, Can Guo wrote:
From: Can Guo <quic_cang@xxxxxxxxxxx>
During host driver init, the phy_gear is set to the minimum supported gear
(HS_G2). Then, during the first power mode change, the negotiated gear, say
HS-G4, is updated to the phy_gear variable so that in the second init the
updated phy_gear can be used to program the PHY.
But the current code only allows update the phy_gear to a higher value. If
one wants to start the first init with the maximum support gear, say HS-G4,
the phy_gear is not updated to HS-G3 if the device only supports HS-G3.
Can you elaborate when this can happen? AFAICS, there are 3 possibilities of
initial phy gear with this series:
1. If ufshc is < 5.0, then G2 will be used.
2. If ufshc is >= 5.0 and if the version is populated in register, then that
gear will be used. Most likely that gear can be G4/G5 depending on the device
connected.
3. If ufshc is >=5.0 and version is not populated, then G4 will be used.
In all the above cases, I do not see any necessity to switch the phy gear
setting to lower one while scaling. Since the gears are backwards compatible,
we always use one phy gear sequence. Moreover, we only have 2 init sequences.
Please correct me if I'm missing anything.
- Mani
In the next patch, I am setting the initial PHY gear to max HS gear read
from UFS host cap register, so that we don't need to keep updating the
initial value for host->phy_gear for different HW versions in future.
FYI, for HW ver 5 and 6, it is HS-G5. In future, the max gear might
become HS-G6 or higher on newer HW verions.
I the case #3, if HS-G5 is set to host->phy_gear, the first init uses
HS-G5, then after negotiation if the agreed gear is HS-G4, we need to
update host->phy_gear to HS-G4 (a lower value) such that we use a power
saving PHY gear settings during the 2nd init.
If the commit message is making you confused, I can update it in next
version. Please let me if I made any mistakes here.
Thanks,
Can Guo.
