diff mbox series

[v1,2/3] clk: tegra: ignore unused vfir clock shared with uartb

Message ID 20181101015230.27310-3-marcel@ziswiler.com (mailing list archive)
State Changes Requested, archived
Headers show
Series clk/serial tegra: uart related fixes | expand

Commit Message

Marcel Ziswiler Nov. 1, 2018, 1:52 a.m. UTC 
From: Marcel Ziswiler <marcel.ziswiler@toradex.com>

As UARTB and VFIR share their clock enable bit it is rather unwise for
the kernel to turn off the VFIR one should that be unused (and
potentially vice versa but so far there anyway is no VFIR driver).

Without this patch trying to use UARTB with the regular 8250 driver
will freeze as soon as ttyS1 is accessed after boot. Luckily, using the
high-speed Tegra serial driver won't exhibit the issue as clocks are
dynamically enabled/disabled on every access.

This has been reproduced both on Apalis T30 as well as Apalis TK1 but
may be an issue on all Tegra UARTB's which share the clock enable with
VFIR.

Reported-by: Kory Swain <kory.swain@trapezegroup.com>
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>

---

 drivers/clk/tegra/clk-tegra-periph.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Peter De Schrijver Nov. 1, 2018, 8:41 a.m. UTC | #1 
On Thu, Nov 01, 2018 at 02:52:29AM +0100, Marcel Ziswiler wrote:
> From: Marcel Ziswiler <marcel.ziswiler@toradex.com>
> 
> As UARTB and VFIR share their clock enable bit it is rather unwise for
> the kernel to turn off the VFIR one should that be unused (and
> potentially vice versa but so far there anyway is no VFIR driver).
> 
> Without this patch trying to use UARTB with the regular 8250 driver
> will freeze as soon as ttyS1 is accessed after boot. Luckily, using the
> high-speed Tegra serial driver won't exhibit the issue as clocks are
> dynamically enabled/disabled on every access.
> 
> This has been reproduced both on Apalis T30 as well as Apalis TK1 but
> may be an issue on all Tegra UARTB's which share the clock enable with
> VFIR.
> 

Ah.. the correct fix for this is to initialize the enable_refcnt based on the
hw state. This is done in 9619dba8325fce098bbc9ee2911d1b0150fec0c9 for
periph gate clocks, but obviously also applies to normal periph clocks.

Peter.

> Reported-by: Kory Swain <kory.swain@trapezegroup.com>
> Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
> 
> ---
> 
>  drivers/clk/tegra/clk-tegra-periph.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/tegra/clk-tegra-periph.c b/drivers/clk/tegra/clk-tegra-periph.c
> index cc5275ec2c01..116c74340fb7 100644
> --- a/drivers/clk/tegra/clk-tegra-periph.c
> +++ b/drivers/clk/tegra/clk-tegra-periph.c
> @@ -668,7 +668,7 @@ static struct tegra_periph_init_data periph_clks[] = {
>  	MUX("hda", mux_pllp_pllc_clkm, CLK_SOURCE_HDA, 125, TEGRA_PERIPH_ON_APB, tegra_clk_hda_8),
>  	MUX("hda2codec_2x", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_HDA2CODEC_2X, 111, TEGRA_PERIPH_ON_APB, tegra_clk_hda2codec_2x),
>  	MUX8("hda2codec_2x", mux_pllp_pllc_plla_clkm, CLK_SOURCE_HDA2CODEC_2X, 111, TEGRA_PERIPH_ON_APB, tegra_clk_hda2codec_2x_8),
> -	MUX("vfir", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_VFIR, 7, TEGRA_PERIPH_ON_APB, tegra_clk_vfir),
> +	MUX_FLAGS("vfir", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_VFIR, 7, TEGRA_PERIPH_ON_APB, tegra_clk_vfir, CLK_IGNORE_UNUSED),
>  	MUX("sdmmc1", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_SDMMC1, 14, TEGRA_PERIPH_ON_APB, tegra_clk_sdmmc1),
>  	MUX("sdmmc2", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_SDMMC2, 9, TEGRA_PERIPH_ON_APB, tegra_clk_sdmmc2),
>  	MUX("sdmmc3", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_SDMMC3, 69, TEGRA_PERIPH_ON_APB, tegra_clk_sdmmc3),
> -- 
> 2.14.5
>
Thierry Reding Nov. 28, 2018, 9:24 a.m. UTC | #2 
On Thu, Nov 01, 2018 at 10:41:52AM +0200, Peter De Schrijver wrote:
> On Thu, Nov 01, 2018 at 02:52:29AM +0100, Marcel Ziswiler wrote:
> > From: Marcel Ziswiler <marcel.ziswiler@toradex.com>
> > 
> > As UARTB and VFIR share their clock enable bit it is rather unwise for
> > the kernel to turn off the VFIR one should that be unused (and
> > potentially vice versa but so far there anyway is no VFIR driver).
> > 
> > Without this patch trying to use UARTB with the regular 8250 driver
> > will freeze as soon as ttyS1 is accessed after boot. Luckily, using the
> > high-speed Tegra serial driver won't exhibit the issue as clocks are
> > dynamically enabled/disabled on every access.
> > 
> > This has been reproduced both on Apalis T30 as well as Apalis TK1 but
> > may be an issue on all Tegra UARTB's which share the clock enable with
> > VFIR.
> > 
> 
> Ah.. the correct fix for this is to initialize the enable_refcnt based on the
> hw state. This is done in 9619dba8325fce098bbc9ee2911d1b0150fec0c9 for
> periph gate clocks, but obviously also applies to normal periph clocks.

Hi Marcel,

were you going to send a new version with the alternative fix as
suggested by Peter?

Thierry
Marcel Ziswiler Dec. 10, 2018, 9:41 p.m. UTC | #3 
On November 28, 2018 10:24:04 AM GMT+01:00, Thierry Reding <thierry.reding@gmail.com> wrote:
>On Thu, Nov 01, 2018 at 10:41:52AM +0200, Peter De Schrijver wrote:
>> On Thu, Nov 01, 2018 at 02:52:29AM +0100, Marcel Ziswiler wrote:
>> > From: Marcel Ziswiler <marcel.ziswiler@toradex.com>
>> > 
>> > As UARTB and VFIR share their clock enable bit it is rather unwise
>for
>> > the kernel to turn off the VFIR one should that be unused (and
>> > potentially vice versa but so far there anyway is no VFIR driver).
>> > 
>> > Without this patch trying to use UARTB with the regular 8250 driver
>> > will freeze as soon as ttyS1 is accessed after boot. Luckily, using
>the
>> > high-speed Tegra serial driver won't exhibit the issue as clocks
>are
>> > dynamically enabled/disabled on every access.
>> > 
>> > This has been reproduced both on Apalis T30 as well as Apalis TK1
>but
>> > may be an issue on all Tegra UARTB's which share the clock enable
>with
>> > VFIR.
>> > 
>> 
>> Ah.. the correct fix for this is to initialize the enable_refcnt
>based on the
>> hw state. This is done in 9619dba8325fce098bbc9ee2911d1b0150fec0c9
>for
>> periph gate clocks, but obviously also applies to normal periph
>clocks.
>
>Hi Marcel,
>
>were you going to send a new version with the alternative fix as
>suggested by Peter?

Yes, sorry. Let me look at that now.

>Thierry
diff mbox series

Patch

diff --git a/drivers/clk/tegra/clk-tegra-periph.c b/drivers/clk/tegra/clk-tegra-periph.c
index cc5275ec2c01..116c74340fb7 100644
--- a/drivers/clk/tegra/clk-tegra-periph.c
+++ b/drivers/clk/tegra/clk-tegra-periph.c
@@ -668,7 +668,7 @@  static struct tegra_periph_init_data periph_clks[] = {
 	MUX("hda", mux_pllp_pllc_clkm, CLK_SOURCE_HDA, 125, TEGRA_PERIPH_ON_APB, tegra_clk_hda_8),
 	MUX("hda2codec_2x", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_HDA2CODEC_2X, 111, TEGRA_PERIPH_ON_APB, tegra_clk_hda2codec_2x),
 	MUX8("hda2codec_2x", mux_pllp_pllc_plla_clkm, CLK_SOURCE_HDA2CODEC_2X, 111, TEGRA_PERIPH_ON_APB, tegra_clk_hda2codec_2x_8),
-	MUX("vfir", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_VFIR, 7, TEGRA_PERIPH_ON_APB, tegra_clk_vfir),
+	MUX_FLAGS("vfir", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_VFIR, 7, TEGRA_PERIPH_ON_APB, tegra_clk_vfir, CLK_IGNORE_UNUSED),
 	MUX("sdmmc1", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_SDMMC1, 14, TEGRA_PERIPH_ON_APB, tegra_clk_sdmmc1),
 	MUX("sdmmc2", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_SDMMC2, 9, TEGRA_PERIPH_ON_APB, tegra_clk_sdmmc2),
 	MUX("sdmmc3", mux_pllp_pllc_pllm_clkm, CLK_SOURCE_SDMMC3, 69, TEGRA_PERIPH_ON_APB, tegra_clk_sdmmc3),