> -----Original Message----- > From: Marco Felsch <m.felsch@xxxxxxxxxxxxxx> > Sent: Wednesday, August 24, 2022 4:04 PM > To: Alice Guo (OSS) <alice.guo@xxxxxxxxxxx> > Cc: Guenter Roeck <linux@xxxxxxxxxxxx>; wim@xxxxxxxxxxxxxxxxxx; > shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > dl-linux-imx <linux-imx@xxxxxxx>; kernel@xxxxxxxxxxxxxx; > linux-watchdog@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 2/7] watchdog: imx7ulp: Add explict memory barrier for > unlock sequence > > Hi Alice, > > On 22-08-24, Alice Guo (OSS) wrote: > > ... > > > > > > Hi Guenter and Marco, > > > > > > > > > > 1. did you see any issues? > > > > > This WDOG Timer first appeared in i.MX7ULP, no one report issues > > > > > probably because few people use i.MX7ULP. This issue was found > > > > > when we did a stress test on it. When we reconfigure the WDOG > > > > > Timer, there is a certain probability that it reset. The reason > > > > > for the error is that when WDOG_CS[CMD32EN] is 0, the unlock > > > > > sequence is two 16-bit writes (0xC520, 0xD928) to the CNT > > > > > register within 16 bus clocks, and improper unlock sequence causes the > WDOG to reset. > > > > > Adding mb() is to guarantee that two 16-bit writes are finished > > > > > within 16 > > > bus clocks. > > > > > > > > After this explanation the whole imx7ulp_wdt_init() seems a bit > > > > buggy because writel_relaxed() as well as writel() are 32bit access > functions. > > > > So the very first thing to do is to enable the 32-bit mode. > > > > > > > Agreed. This is much better than having extra code to deal with both > > > 16-bit and 32-bit access. > > > > > > > Also this is a explanation worth to be added to the commit message > > > > ;) > > > > > > > > > > Definitely. Also, the use of mb(), if it should indeed be needed, > > > would have to be explained in a code comment. > > > > > > Thanks, > > > Guenter > > > > Hi Marco and Guenter, > > > > Thank you for your comments. I plan to enable support for 32-bit > > unlock command write words in bootloader. In this way, there is no > > need to distinguish whether the unlock command is a 32-bit command or > > a 16-bit command in driver. > > Please don't move this into the bootloader, enabling it within the init seq. is > just fine. If you move it into the bootloader then you can't ensure that the bit is > set since there are plenty of bootloaders out there. > > As I said, just drop the "16bit" unlock sequence from the init function because > the unlock is handled just fine in all the watchdog_ops. > > Regards, > Marco Hi Marco, Sorry, I did not tell you that all watchdog control bits, timeout value, and window value cannot be set until the watchdog is unlocked. Support for 32-bit unlock command write words in enabled in imx7ulp_wdt_init now. Best Regards, Alice Guo
