[PATCH] Revert "clk: imx: fix composite peripheral flags"

[PATCH] Revert "clk: imx: fix composite peripheral flags"

[Martin Kepplinger]

This reverts commit 936c383673b9e3007432f17140ac62de53d87db9.

It breaks clock reparenting via devfreq on the imx8mq used in the
Librem 5 phone. When switching dram frequency (which worked before)
the system now hangs after this where the dram_apb clock cannot be
set:

[  129.391755] imx8m-ddrc-devfreq 3d400000.memory-controller: failed to
set dram_apb parent: -16
[  129.391959] imx8m-ddrc-devfreq 3d400000.memory-controller: ddrc
failed freq switch to 25000000 from 800000000: error -16. now at 25000000
[  129.406133] imx8m-ddrc-devfreq 3d400000.memory-controller: failed to
update frequency from PM QoS (-16)

Note that on the Librem 5 devkit that uses a different revision of the
imx8mq SoC, the added flag does *not* break said clock reparenting so
there might be subtle differences here.

Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>
---
 drivers/clk/imx/clk-composite-8m.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/clk/imx/clk-composite-8m.c b/drivers/clk/imx/clk-composite-8m.c
index 2c309e3dc8e3..78fb7e52a42a 100644
--- a/drivers/clk/imx/clk-composite-8m.c
+++ b/drivers/clk/imx/clk-composite-8m.c
@@ -216,7 +216,6 @@ struct clk_hw *imx8m_clk_hw_composite_flags(const char *name,
 		div->width = PCG_PREDIV_WIDTH;
 		divider_ops = &imx8m_clk_composite_divider_ops;
 		mux_ops = &clk_mux_ops;
-		flags |= CLK_SET_PARENT_GATE;
 	}
 
 	div->lock = &imx_ccm_lock;
-- 
2.20.1

Re: [PATCH] Revert "clk: imx: fix composite peripheral flags"

[Fabio Estevam]

Hi Martin,

On Thu, Dec 31, 2020 at 11:22 AM Martin Kepplinger
<martin.kepplinger@puri.sm> wrote:
>
> This reverts commit 936c383673b9e3007432f17140ac62de53d87db9.
>
> It breaks clock reparenting via devfreq on the imx8mq used in the
> Librem 5 phone. When switching dram frequency (which worked before)
> the system now hangs after this where the dram_apb clock cannot be
> set:
>
> [  129.391755] imx8m-ddrc-devfreq 3d400000.memory-controller: failed to
> set dram_apb parent: -16
> [  129.391959] imx8m-ddrc-devfreq 3d400000.memory-controller: ddrc
> failed freq switch to 25000000 from 800000000: error -16. now at 25000000
> [  129.406133] imx8m-ddrc-devfreq 3d400000.memory-controller: failed to
> update frequency from PM QoS (-16)

I am wondering whether IMX8MQ_CLK_DRAM_ALT should also be marked as
CLK_IS_CRITICAL.

Could you please try the following change without the revert?

--- a/drivers/clk/imx/clk-imx8mq.c
+++ b/drivers/clk/imx/clk-imx8mq.c
@@ -458,7 +458,7 @@ static int imx8mq_clocks_probe(struct platform_device *pdev)
         * Mark with GET_RATE_NOCACHE to always read div value from hardware
         */
        hws[IMX8MQ_CLK_DRAM_CORE] =
imx_clk_hw_mux2_flags("dram_core_clk", base + 0x9800, 24, 1,
imx8mq_dram_core_sels, ARRAY_SIZE(imx8mq_dram_core_sels),
CLK_IS_CRITICAL);
-       hws[IMX8MQ_CLK_DRAM_ALT] =
__imx8m_clk_hw_composite("dram_alt", imx8mq_dram_alt_sels, base +
0xa000, CLK_GET_RATE_NOCACHE);
+       hws[IMX8MQ_CLK_DRAM_ALT] =
__imx8m_clk_hw_composite("dram_alt", imx8mq_dram_alt_sels, base +
0xa000, CLK_IS_CRITICAL | CLK_GET_RATE_NOCACHE);
        hws[IMX8MQ_CLK_DRAM_APB] =
__imx8m_clk_hw_composite("dram_apb", imx8mq_dram_apb_sels, base +
0xa080, CLK_IS_CRITICAL | CLK_GET_RATE_NOCACHE);

Thanks

Re: [PATCH] Revert "clk: imx: fix composite peripheral flags"

[Abel Vesa]

On 20-12-31 17:33:40, Fabio Estevam wrote:
> Hi Martin,
> 
> On Thu, Dec 31, 2020 at 11:22 AM Martin Kepplinger
> <martin.kepplinger@puri.sm> wrote:
> >
> > This reverts commit 936c383673b9e3007432f17140ac62de53d87db9.
> >
> > It breaks clock reparenting via devfreq on the imx8mq used in the
> > Librem 5 phone. When switching dram frequency (which worked before)
> > the system now hangs after this where the dram_apb clock cannot be
> > set:
> >
> > [  129.391755] imx8m-ddrc-devfreq 3d400000.memory-controller: failed to
> > set dram_apb parent: -16
> > [  129.391959] imx8m-ddrc-devfreq 3d400000.memory-controller: ddrc
> > failed freq switch to 25000000 from 800000000: error -16. now at 25000000
> > [  129.406133] imx8m-ddrc-devfreq 3d400000.memory-controller: failed to
> > update frequency from PM QoS (-16)
> 
> I am wondering whether IMX8MQ_CLK_DRAM_ALT should also be marked as
> CLK_IS_CRITICAL.
> 

Hmm, the way the DRAM clocks are right registered right now is a real mess.
The DRAM clocks on i.MX8M are changed in TF-A, but the kernel still needs to
register them to keep track of the clock tree.

Martin, I already have a patchset waiting to be shipped which doesn't 
only fix the 8MQ, but all the 8M platforms. Unfortunately, I haven't had the time
to work on that in the last couple of weeks but I intend to switch back to it soon.

Fabio, marking the DRAM clocks as critical will not allow the set_parent to be done,
as CLK_IS_CRITICAL flag and set_parent do not go together. As of now the devfreq
tries to reparent to be consistent with TF-A configuration.

My approach here was to make the DRAM clocks read-only. This means adding some 
stuff in the clock core subsystem too.

> Could you please try the following change without the revert?
> 
> --- a/drivers/clk/imx/clk-imx8mq.c
> +++ b/drivers/clk/imx/clk-imx8mq.c
> @@ -458,7 +458,7 @@ static int imx8mq_clocks_probe(struct platform_device *pdev)
>          * Mark with GET_RATE_NOCACHE to always read div value from hardware
>          */
>         hws[IMX8MQ_CLK_DRAM_CORE] =
> imx_clk_hw_mux2_flags("dram_core_clk", base + 0x9800, 24, 1,
> imx8mq_dram_core_sels, ARRAY_SIZE(imx8mq_dram_core_sels),
> CLK_IS_CRITICAL);
> -       hws[IMX8MQ_CLK_DRAM_ALT] =
> __imx8m_clk_hw_composite("dram_alt", imx8mq_dram_alt_sels, base +
> 0xa000, CLK_GET_RATE_NOCACHE);
> +       hws[IMX8MQ_CLK_DRAM_ALT] =
> __imx8m_clk_hw_composite("dram_alt", imx8mq_dram_alt_sels, base +
> 0xa000, CLK_IS_CRITICAL | CLK_GET_RATE_NOCACHE);
>         hws[IMX8MQ_CLK_DRAM_APB] =
> __imx8m_clk_hw_composite("dram_apb", imx8mq_dram_apb_sels, base +
> 0xa080, CLK_IS_CRITICAL | CLK_GET_RATE_NOCACHE);
> 
> Thanks

Re: [PATCH] Revert "clk: imx: fix composite peripheral flags"

[Martin Kepplinger]

On 04.01.21 13:05, Abel Vesa wrote:
> On 20-12-31 17:33:40, Fabio Estevam wrote:
>> Hi Martin,
>>
>> On Thu, Dec 31, 2020 at 11:22 AM Martin Kepplinger
>> <martin.kepplinger@puri.sm> wrote:
>>>
>>> This reverts commit 936c383673b9e3007432f17140ac62de53d87db9.
>>>
>>> It breaks clock reparenting via devfreq on the imx8mq used in the
>>> Librem 5 phone. When switching dram frequency (which worked before)
>>> the system now hangs after this where the dram_apb clock cannot be
>>> set:
>>>
>>> [  129.391755] imx8m-ddrc-devfreq 3d400000.memory-controller: failed to
>>> set dram_apb parent: -16
>>> [  129.391959] imx8m-ddrc-devfreq 3d400000.memory-controller: ddrc
>>> failed freq switch to 25000000 from 800000000: error -16. now at 25000000
>>> [  129.406133] imx8m-ddrc-devfreq 3d400000.memory-controller: failed to
>>> update frequency from PM QoS (-16)
>>
>> I am wondering whether IMX8MQ_CLK_DRAM_ALT should also be marked as
>> CLK_IS_CRITICAL.
>>
> 
> Hmm, the way the DRAM clocks are right registered right now is a real mess.
> The DRAM clocks on i.MX8M are changed in TF-A, but the kernel still needs to
> register them to keep track of the clock tree.
> 
> Martin, I already have a patchset waiting to be shipped which doesn't
> only fix the 8MQ, but all the 8M platforms. Unfortunately, I haven't had the time
> to work on that in the last couple of weeks but I intend to switch back to it soon.
> 
> Fabio, marking the DRAM clocks as critical will not allow the set_parent to be done,
> as CLK_IS_CRITICAL flag and set_parent do not go together. As of now the devfreq
> tries to reparent to be consistent with TF-A configuration.
> 
> My approach here was to make the DRAM clocks read-only. This means adding some
> stuff in the clock core subsystem too.

Hi Abel, thanks a lot for the update. I'm looking forward to seeing your 
patchset.

                               martin