[PATCH net-next v2 4/4] net: ipa: relax 64-bit build requirement
From: Alex Elder
Date: Thu Mar 18 2021 - 09:52:42 EST
We currently assume the IPA driver is built only for a 64 bit kernel.
When this constraint was put in place it eliminated some do_div()
calls, replacing them with the "/" and "%" operators. We now only
use these operations on u32 and size_t objects. In a 32-bit kernel
build, size_t will be 32 bits wide, so there remains no reason to
use do_div() for divide and modulo.
A few recent commits also fix some code that assumes that DMA
addresses are 64 bits wide.
With that, we can get rid of the 64-bit build requirement.
Signed-off-by: Alex Elder <elder@xxxxxxxxxx>
drivers/net/ipa/Kconfig | 2 +-
drivers/net/ipa/ipa_main.c | 10 ++++++++--
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/net/ipa/Kconfig b/drivers/net/ipa/Kconfig
index b68f1289b89ef..90a90262e0d07 100644
@@ -1,6 +1,6 @@
tristate "Qualcomm IPA support"
- depends on 64BIT && NET && QCOM_SMEM
+ depends on NET && QCOM_SMEM
depends on ARCH_QCOM || COMPILE_TEST
depends on QCOM_RPROC_COMMON || (QCOM_RPROC_COMMON=n && COMPILE_TEST)
select QCOM_MDT_LOADER if ARCH_QCOM
diff --git a/drivers/net/ipa/ipa_main.c b/drivers/net/ipa/ipa_main.c
index 97c1b55405cbf..d354e3e65ec50 100644
@@ -735,8 +735,14 @@ MODULE_DEVICE_TABLE(of, ipa_match);
static void ipa_validate_build(void)
- /* We assume we're working on 64-bit hardware */
+ /* At one time we assumed a 64-bit build, allowing some do_div()
+ * calls to be replaced by simple division or modulo operations.
+ * We currently only perform divide and modulo operations on u32,
+ * u16, or size_t objects, and of those only size_t has any chance
+ * of being a 64-bit value. (It should be guaranteed 32 bits wide
+ * on a 32-bit build, but there is no harm in verifying that.)
+ BUILD_BUG_ON(!IS_ENABLED(CONFIG_64BIT) && sizeof(size_t) != 4);
/* Code assumes the EE ID for the AP is 0 (zeroed structure field) */
BUILD_BUG_ON(GSI_EE_AP != 0);