Hi Geert,
Thanks for your patch.
On 2020-12-10 20:46:48 +0100, Geert Uytterhoeven wrote:
> The Renesas Compare Match Timer 0 and 1 (CMT0/1) variants have a
> register to control the clock supply to the individual channels.
> Currently the driver does not touch this register, and relies on the
> documented initial value, which has the clock supply enabled for all
> channels present.
>
> However, when Linux starts on the APE6-EVM development board, only the
> clock supply to the first CMT1 channel is enabled. Hence the first
> channel (used as a clockevent) works, while the second channel (used as
> a clocksource) does not. Note that the default system clocksource is
> the Cortex-A15 architectured timer, and the user needs to manually
> switch to the CMT1 clocksource to trigger the broken behavior.
>
> Fix this by removing the fragile dependency on implicit reset and/or
> boot loader state, and by enabling the clock supply explicitly for all
> channels used instead. This requires postponing the clk_disable() call,
> else the timer's registers cannot be accessed in sh_cmt_setup_channel().
>
> Signed-off-by: Geert Uytterhoeven <geert+rene...@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+rene...@ragnatech.se>
> ---
> Tested on R-Mobile APE6, R-Car M2-W, and R-Car H3 ES2.0.
> ---
> drivers/clocksource/sh_cmt.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/clocksource/sh_cmt.c b/drivers/clocksource/sh_cmt.c
> index e258230d432c0002..c98f8851fd680454 100644
> --- a/drivers/clocksource/sh_cmt.c
> +++ b/drivers/clocksource/sh_cmt.c
> @@ -235,6 +235,8 @@ static const struct sh_cmt_info sh_cmt_info[] = {
> #define CMCNT 1 /* channel register */
> #define CMCOR 2 /* channel register */
>
> +#define CMCLKE 0x1000 /* CLK Enable Register (R-Car Gen2) */
> +
> static inline u32 sh_cmt_read_cmstr(struct sh_cmt_channel *ch)
> {
> if (ch->iostart)
> @@ -853,6 +855,7 @@ static int sh_cmt_setup_channel(struct sh_cmt_channel
> *ch, unsigned int index,
> unsigned int hwidx, bool clockevent,
> bool clocksource, struct sh_cmt_device *cmt)
> {
> + u32 value;
> int ret;
>
> /* Skip unused channels. */
> @@ -882,6 +885,11 @@ static int sh_cmt_setup_channel(struct sh_cmt_channel
> *ch, unsigned int index,
> ch->iostart = cmt->mapbase + ch->hwidx * 0x100;
> ch->ioctrl = ch->iostart + 0x10;
> ch->timer_bit = 0;
> +
> + /* Enable the clock supply to the channel */
> + value = ioread32(cmt->mapbase + CMCLKE);
> + value |= BIT(hwidx);
> + iowrite32(value, cmt->mapbase + CMCLKE);
> break;
> }
>
> @@ -1014,12 +1022,10 @@ static int sh_cmt_setup(struct sh_cmt_device *cmt,
> struct platform_device *pdev)
> else
> cmt->rate = clk_get_rate(cmt->clk) / 8;
>
> - clk_disable(cmt->clk);
> -
> /* Map the memory resource(s). */
> ret = sh_cmt_map_memory(cmt);
> if (ret < 0)
> - goto err_clk_unprepare;
> + goto err_clk_disable;
>
> /* Allocate and setup the channels. */
> cmt->num_channels = hweight8(cmt->hw_channels);
> @@ -1047,6 +1053,8 @@ static int sh_cmt_setup(struct sh_cmt_device *cmt,
> struct platform_device *pdev)
> mask &= ~(1 << hwidx);
> }
>
> + clk_disable(cmt->clk);
> +
> platform_set_drvdata(pdev, cmt);
>
> return 0;
> @@ -1054,6 +1062,8 @@ static int sh_cmt_setup(struct sh_cmt_device *cmt,
> struct platform_device *pdev)
> err_unmap:
> kfree(cmt->channels);
> iounmap(cmt->mapbase);
> +err_clk_disable:
> + clk_disable(cmt->clk);
> err_clk_unprepare:
> clk_unprepare(cmt->clk);
> err_clk_put:
> --
> 2.25.1
>
--
Regards,
Niklas Söderlund
