On Tue, May 11, 2021 at 07:00:34PM +0300, Dmitry Osipenko wrote: > 11.05.2021 18:31, Krzysztof Kozlowski пишет: > ... > ~~~~~~~~~~~~~~~~~~~~~^ > >>>>> drivers/memory/tegra/tegra124-emc.c:802:26: warning: implicit conversion from 'unsigned long' to 'u32' (aka 'unsigned int') changes value from 18446744071562067985 to 2147483665 [-Wconstant-conversion] > >>> emc_ccfifo_writel(emc, EMC_ZQ_CAL_LONG_CMD_DEV0, EMC_ZQ_CAL); > >>> ~~~~~~~~~~~~~~~~~ ^~~~~~~~~~~~~~~~~~~~~~~~ > >>> drivers/memory/tegra/tegra124-emc.c:154:36: note: expanded from macro 'EMC_ZQ_CAL_LONG_CMD_DEV0' > >>> (DRAM_DEV_SEL_0 | EMC_ZQ_CAL_LONG | EMC_ZQ_CAL_CMD) > >>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~ > >>> 13 warnings generated. > >> > >> This doesn't look like a useful warning from clang, it should see that > >> the constant value itself isn't truncated, hence it should be a problem > >> of clang. Do you think it's okay to ignore this nonsense? > > > > I admit I also do not see the real issue here. The DRAM_DEV_SEL_0 fits > > in u32 and there is no other bitwise arithmetic than just OR, so why > > clang assumes it can have 32 most signifcant bits toggled on? > > > > +Cc Nathan and Nick, > > Maybe you could shed some light here on this warning? > > > > Dmitry, > > In general you should not ignore it because: > > 1. This breaks allyesconfig with clang on powerpc (or it is one of the > > stoppers), > > 2. We might want in some future to build it with clang. > > I meant to ignore it from the perspective of the memory drivers, i.e. it > likely should be fixed in clang and not worked around in the code. Thank > you for pinging the right people. I do not think this is a bug in clang, gcc warns the same (just not here in this case): https://godbolt.org/z/e9GWobMnd DRAM_DEV_SEL_0 and DRAM_DEV_SEL_1 are implicitly signed integers because there is no suffix on the literal 1. DRAM_DEV_SEL_0 is 2 << 30, which can be turned into 1 << 31. That is equal to INT_MAX + 1, which then overflows and becomes INT_MIN (undefined behavior). INT_MIN is then promoted to unsigned long because EMC_ZQ_CAL_LONG and EMC_ZQ_CAL_CMD are unsigned long due to the BIT macro, resulting in the gigantic number that clang reports above. I assume that this driver only runs on hardware where unsigned int is the same size as unsigned long, meaning this problem is merely theoretical? Regardless, defining DRAM_DEV_SEL_{0,1} with the BIT macro fixes the warning for me and should make everything work as expected. diff --git a/drivers/memory/tegra/tegra124-emc.c b/drivers/memory/tegra/tegra124-emc.c index 5699d909abc2..a21ca8e0841a 100644 --- a/drivers/memory/tegra/tegra124-emc.c +++ b/drivers/memory/tegra/tegra124-emc.c @@ -272,8 +272,8 @@ #define EMC_PUTERM_ADJ 0x574 #define DRAM_DEV_SEL_ALL 0 -#define DRAM_DEV_SEL_0 (2 << 30) -#define DRAM_DEV_SEL_1 (1 << 30) +#define DRAM_DEV_SEL_0 BIT(31) +#define DRAM_DEV_SEL_1 BIT(30) #define EMC_CFG_POWER_FEATURES_MASK \ (EMC_CFG_DYN_SREF | EMC_CFG_DRAM_ACPD | EMC_CFG_DRAM_CLKSTOP_SR | \
