Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933709AbcJFTD7 (ORCPT ); Thu, 6 Oct 2016 15:03:59 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:36380 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751137AbcJFTD6 (ORCPT ); Thu, 6 Oct 2016 15:03:58 -0400 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 06 Oct 2016 12:03:56 -0700 From: Subhash Jadavani To: Kiwoong Kim Cc: vinholikatti@gmail.com, jejb@linux.vnet.ibm.com, martin.petersen@oracle.com, "'open list:UNIVERSAL FLASH STORAGE HOST CONTROLLER DRIVER'" , "'open list'" , linux-scsi-owner@vger.kernel.org Subject: Re: [PATCH v2] scsi: ufshcd: fix possible unclocked register access In-Reply-To: <000401d21fbc$62fd3600$28f7a200$@samsung.com> References: <1475720241-25836-1-git-send-email-subhashj@codeaurora.org> <000401d21fbc$62fd3600$28f7a200$@samsung.com> Message-ID: User-Agent: Roundcube Webmail/1.2.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3966 Lines: 122 Thanks Kim for the response. On 2016-10-06 03:28, Kiwoong Kim wrote: > Hi, Subhash. > > Some UFS host controllers may need to call the vendor specific callback > before and after controlling by clock control framework, > regardless of whether available clocks are turned on or off. Are you suggesting to call ufshcd_vops_setup_clocks() 2 times, one before the on/off by ufshcd core driver and one after the on/off? If yes, then we also have add 3rd argument clarifying if this is PRE_CHANGE or POST_CHANGE. > > Is there any special reason to limit to invoke the callback > only when the clocks are turned on or not? > > Besides, the callback is acknowledged from core driver > because 2nd argument is whether the clocks are turned on or not. > > If you have any other idea, please let me know. This is my suggestion: 1. Add 3rd argument to setup_clocks ops to let the vendor callback function know if this is called PRE_CHANGE or POST_CHANGE. 2. If #1 is in place, call setup_clocks 2 times, one with PRE_CHANGE argument before making any clock changes in core driver, 2nd with POST_CHANGE argument after making the clock changes to core driver. Let me know if this would work or not. Thanks, Subhash > > Thanks > Regards > >> Vendor specific setup_clocks callback may require the clocks managed >> by ufshcd driver to be ON. So if the vendor specific setup_clocks >> callback >> is called while the required clocks are turned off, it could result >> into >> unclocked register access. >> >> To prevent possible unclock register access, this change makes sure >> that >> required clocks remain enabled before calling into vendor specific >> setup_clocks callback. >> >> Signed-off-by: Subhash Jadavani >> --- >> Changes from v2: >> * Don't call ufshcd_vops_setup_clocks() again for clock off >> --- >> drivers/scsi/ufs/ufshcd.c | 22 +++++++++++++++++++++- >> 1 file changed, 21 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c >> index 05c7456..c1a77d3 100644 >> --- a/drivers/scsi/ufs/ufshcd.c >> +++ b/drivers/scsi/ufs/ufshcd.c >> @@ -5389,6 +5389,17 @@ static int __ufshcd_setup_clocks(struct ufs_hba >> *hba, bool on, >> if (!head || list_empty(head)) >> goto out; >> >> + /* >> + * vendor specific setup_clocks ops may depend on clocks managed by >> + * this standard driver hence call the vendor specific setup_clocks >> + * before disabling the clocks managed here. >> + */ >> + if (!on) { >> + ret = ufshcd_vops_setup_clocks(hba, on); >> + if (ret) >> + return ret; >> + } >> + >> list_for_each_entry(clki, head, list) { >> if (!IS_ERR_OR_NULL(clki->clk)) { >> if (skip_ref_clk && !strcmp(clki->name, "ref_clk")) >> @@ -5410,7 +5421,16 @@ static int __ufshcd_setup_clocks(struct ufs_hba >> *hba, bool on, >> } >> } >> >> - ret = ufshcd_vops_setup_clocks(hba, on); >> + /* >> + * vendor specific setup_clocks ops may depend on clocks managed by >> + * this standard driver hence call the vendor specific setup_clocks >> + * after enabling the clocks managed here. >> + */ >> + if (on) { >> + ret = ufshcd_vops_setup_clocks(hba, on); >> + if (ret) >> + return ret; >> + } >> out: >> if (ret) { >> list_for_each_entry(clki, head, list) { >> -- >> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora >> Forum, >> a Linux Foundation Collaborative Project >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-scsi" >> in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-scsi" > in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project