Messages in this thread Patch in this message | | | Subject | Re: [PATCH v2 2/2] soc: mediatek: add a fixed wait for SRAM stable | From | Sean Wang <> | Date | Mon, 30 Apr 2018 15:08:00 +0800 |
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On Fri, 2018-04-27 at 11:46 +0200, Matthias Brugger wrote: > Hi Sean, > > On 04/23/2018 11:39 AM, Sean Wang wrote: > > On Mon, 2018-04-23 at 11:31 +0200, Matthias Brugger wrote: > >> > >> On 04/23/2018 10:36 AM, sean.wang@mediatek.com wrote: > >>> From: Sean Wang <sean.wang@mediatek.com> > >>> > >>> MT7622_POWER_DOMAIN_WB doesn't send an ACK when its managed SRAM becomes > >>> stable, which is not like the behavior the other power domains should > >>> have. Therefore, it's necessary for such a power domain to have a fixed > >>> and well-predefined duration to wait until its managed SRAM can be allowed > >>> to access by all functions running on the top. > >>> > >>> v1 -> v2: > >>> - use MTK_SCPD_FWAIT_SRAM flag as an indication requiring force waiting. > >>> > >>> Signed-off-by: Sean Wang <sean.wang@mediatek.com> > >>> Cc: Matthias Brugger <matthias.bgg@gmail.com> > >>> Cc: Ulf Hansson <ulf.hansson@linaro.org> > >>> Cc: Weiyi Lu <weiyi.lu@mediatek.com> > >>> --- > >>> drivers/soc/mediatek/mtk-scpsys.c | 24 ++++++++++++++++++------ > >>> 1 file changed, 18 insertions(+), 6 deletions(-) > >>> > >>> diff --git a/drivers/soc/mediatek/mtk-scpsys.c b/drivers/soc/mediatek/mtk-scpsys.c > >>> index b1b45e4..d4f1a63 100644 > >>> --- a/drivers/soc/mediatek/mtk-scpsys.c > >>> +++ b/drivers/soc/mediatek/mtk-scpsys.c > >>> @@ -32,6 +32,7 @@ > >>> #define MTK_POLL_TIMEOUT (jiffies_to_usecs(HZ)) > >>> > >>> #define MTK_SCPD_ACTIVE_WAKEUP BIT(0) > >>> +#define MTK_SCPD_FWAIT_SRAM BIT(1) > >>> #define MTK_SCPD_CAPS(_scpd, _x) ((_scpd)->data->caps & (_x)) > >>> > >>> #define SPM_VDE_PWR_CON 0x0210 > >>> @@ -237,11 +238,22 @@ static int scpsys_power_on(struct generic_pm_domain *genpd) > >>> val &= ~scpd->data->sram_pdn_bits; > >>> writel(val, ctl_addr); > >>> > >>> - /* wait until SRAM_PDN_ACK all 0 */ > >>> - ret = readl_poll_timeout(ctl_addr, tmp, (tmp & pdn_ack) == 0, > >>> - MTK_POLL_DELAY_US, MTK_POLL_TIMEOUT); > >>> - if (ret < 0) > >>> - goto err_pwr_ack; > >>> + /* Either wait until SRAM_PDN_ACK all 0 or have a force wait */ > >>> + if (!MTK_SCPD_CAPS(scpd, MTK_SCPD_FWAIT_SRAM)) { > > After having another look on the patch, could you change the order of the if: > So that we check for the existence of the MTK_SCPD_FWAIT_SRAM and sleep and in > the else branch we to the readl_poll_timeout. > > I think in the future this will make the code easier to understand as you can > easily oversee the '!' negation in the if. > > Regards, > Matthias >
Initial thought on the patch is that I would like to save a branch instruction for a most possibly executed block. Or would it be better to add a compiler to branch prediction information? something like that
/* Either wait until SRAM_PDN_ACK all 0 or have a force wait */ if (unlikely(MTK_SCPD_CAPS(scpd, MTK_SCPD_FWAIT_SRAM))) { /* * Currently, MTK_SCPD_FWAIT_SRAM is necessary only for * MT7622_POWER_DOMAIN_WB and thus just a trivial setup is * applied here. */ usleep_range(12000, 12100); ...
> > >>> + ret = readl_poll_timeout(ctl_addr, tmp, (tmp & pdn_ack) == 0, > >>> + MTK_POLL_DELAY_US, MTK_POLL_TIMEOUT); > >>> + if (ret < 0) > >>> + goto err_pwr_ack; > >>> + } else { > >>> + /* > >>> + * Currently, MTK_SCPD_FWAIT_SRAM is necessary only for > >>> + * MT7622_POWER_DOMAIN_WB and thus just a trivial setup is > >>> + * applied here. If there're more domains which need to force > >>> + * waiting for its own pre-defined value, the duration should > >>> + * be coded in the caps field. > >>> + */ > >> > >> I would say, if necessary in the future we can add a switch statement here. > >> Other then that the patches look good. If you are OK, I'll just delete the last > >> sentence when applying the patch. > >> > > > > yes, it's okay for me. > > > >> Regards, > >> Matthias > >> > >>> + usleep_range(12000, 12100); > >>> + }; > >>> > >>> if (scpd->data->bus_prot_mask) { > >>> ret = mtk_infracfg_clear_bus_protection(scp->infracfg, > >>> @@ -785,7 +797,7 @@ static const struct scp_domain_data scp_domain_data_mt7622[] = { > >>> .sram_pdn_ack_bits = 0, > >>> .clk_id = {CLK_NONE}, > >>> .bus_prot_mask = MT7622_TOP_AXI_PROT_EN_WB, > >>> - .caps = MTK_SCPD_ACTIVE_WAKEUP, > >>> + .caps = MTK_SCPD_ACTIVE_WAKEUP | MTK_SCPD_FWAIT_SRAM, > >>> }, > >>> }; > >>> > >>> > > > >
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