Re: [PATCH v4] ufs: core: fix lockdep warning of clk_scaling_lock

On 7/26/22 20:21, peter.wang@mediatek.com wrote:

• /* Enable Write Booster if we have scaled up else disable it */
• downgrade_write(&hba->clk_scaling_lock);
• is_writelock = false;
• ufshcd_wb_toggle(hba, scale_up);

• /* Disable clk_scaling until ufshcd_wb_toggle finish */
• hba->clk_scaling.is_allowed = false;
• wb_toggle = true;

out_unprepare:

• ufshcd_clock_scaling_unprepare(hba, is_writelock);

• ufshcd_clock_scaling_unprepare(hba);
• /* Enable Write Booster if we have scaled up else disable it */
• if (wb_toggle) {

• ufshcd_wb_toggle(hba, scale_up);
  

• ufshcd_clk_scaling_allow(hba, true);
  

• }

I'm concerned that briefly disabling clock scaling may cause the clock to remain at a high frequency even if it shouldn't. Has the following approach been considered? Instead of moving the ufshcd_clk_scaling_allow() call, convert dev_cmd.lock into a semaphore, lock it near the start of ufshcd_devfreq_scale() and unlock it near the end of the same function.

Thanks,

Bart.