From: Serge Semin Sergey.Semin@baikalelectronics.ru
[ Upstream commit c388cc804016cf0f65afdc2362b120aa594ff3e6 ]
We have discovered random glitches during the system boot up procedure. The problem investigation led us to the weird outcomes: when none of the Renesas 5P49V6901 ports are explicitly enabled by the kernel driver, the glitches disappeared. It was a mystery since the SoC external clock domains were fed with different 5P49V6901 outputs. The driver code didn't seem like bogus either. We almost despaired to find out a root cause when the solution has been found for a more modern revision of the chip. It turned out the 5P49V6901 clock generator stopped its output for a short period of time during the VC5_OUT_DIV_CONTROL register writing. The same problem was found for the 5P49V6965 revision of the chip and was successfully fixed in commit fc336ae622df ("clk: vc5: fix output disabling when enabling a FOD") by enabling the "bypass_sync" flag hidden inside "Unused Factory Reserved Register". Even though the 5P49V6901 registers description and programming guide doesn't provide any intel regarding that flag, setting it up anyway in the officially unused register completely eliminated the denoted glitches. Thus let's activate the functionality submitted in commit fc336ae622df ("clk: vc5: fix output disabling when enabling a FOD") for the Renesas 5P49V6901 chip too in order to remove the ports implicit inter-dependency.
Fixes: dbf6b16f5683 ("clk: vc5: Add support for IDT VersaClock 5P49V6901") Signed-off-by: Serge Semin Sergey.Semin@baikalelectronics.ru Reviewed-by: Luca Ceresoli luca@lucaceresoli.net Link: https://lore.kernel.org/r/20220929225402.9696-2-Sergey.Semin@baikalelectroni... Signed-off-by: Stephen Boyd sboyd@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/clk/clk-versaclock5.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/clk/clk-versaclock5.c b/drivers/clk/clk-versaclock5.c index c6d3b1ab3d55..5f8bd49b0810 100644 --- a/drivers/clk/clk-versaclock5.c +++ b/drivers/clk/clk-versaclock5.c @@ -1204,7 +1204,7 @@ static const struct vc5_chip_info idt_5p49v6901_info = { .model = IDT_VC6_5P49V6901, .clk_fod_cnt = 4, .clk_out_cnt = 5, - .flags = VC5_HAS_PFD_FREQ_DBL, + .flags = VC5_HAS_PFD_FREQ_DBL | VC5_HAS_BYPASS_SYNC_BIT, };
static const struct vc5_chip_info idt_5p49v6965_info = {