| Message ID | 20201008155154.3.I646736d3969dc47de8daceb379c6ba85993de9f4@changeid (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | i2c: i2c-qcom-geni: More properly fix the DMA race | expand |
Quoting Douglas Anderson (2020-10-08 15:52:35) > diff --git a/drivers/soc/qcom/qcom-geni-se.c b/drivers/soc/qcom/qcom-geni-se.c > index 751a49f6534f..746854745b15 100644 > --- a/drivers/soc/qcom/qcom-geni-se.c > +++ b/drivers/soc/qcom/qcom-geni-se.c > @@ -266,49 +266,53 @@ EXPORT_SYMBOL(geni_se_init); > static void geni_se_select_fifo_mode(struct geni_se *se) > { > u32 proto = geni_se_read_proto(se); > - u32 val; > + u32 val, val_old; > > geni_se_irq_clear(se); > > - val = readl_relaxed(se->base + SE_GENI_M_IRQ_EN); > if (proto != GENI_SE_UART) { > + val_old = val = readl_relaxed(se->base + SE_GENI_M_IRQ_EN); > val |= M_CMD_DONE_EN | M_TX_FIFO_WATERMARK_EN; > val |= M_RX_FIFO_WATERMARK_EN | M_RX_FIFO_LAST_EN; > - } > - writel_relaxed(val, se->base + SE_GENI_M_IRQ_EN); > + if (val != val_old) > + writel_relaxed(val, se->base + SE_GENI_M_IRQ_EN); > > - val = readl_relaxed(se->base + SE_GENI_S_IRQ_EN); > - if (proto != GENI_SE_UART) > - val |= S_CMD_DONE_EN; > - writel_relaxed(val, se->base + SE_GENI_S_IRQ_EN); > + val = readl_relaxed(se->base + SE_GENI_S_IRQ_EN); Can we use the val_old trick here too? > + if (!(val & S_CMD_DONE_EN)) > + writel_relaxed(val | S_CMD_DONE_EN, Because this val | S_CMD_DONE_EN thing is just hard to read :/ > + se->base + SE_GENI_S_IRQ_EN); > + } > > val = readl_relaxed(se->base + SE_GENI_DMA_MODE_EN); > - val &= ~GENI_DMA_MODE_EN; > - writel_relaxed(val, se->base + SE_GENI_DMA_MODE_EN); > + if (val & GENI_DMA_MODE_EN) > + writel_relaxed(val & ~GENI_DMA_MODE_EN, > + se->base + SE_GENI_DMA_MODE_EN); > } >
Hi, On Fri, Oct 9, 2020 at 5:32 PM Stephen Boyd <swboyd@chromium.org> wrote: > > Quoting Douglas Anderson (2020-10-08 15:52:35) > > diff --git a/drivers/soc/qcom/qcom-geni-se.c b/drivers/soc/qcom/qcom-geni-se.c > > index 751a49f6534f..746854745b15 100644 > > --- a/drivers/soc/qcom/qcom-geni-se.c > > +++ b/drivers/soc/qcom/qcom-geni-se.c > > @@ -266,49 +266,53 @@ EXPORT_SYMBOL(geni_se_init); > > static void geni_se_select_fifo_mode(struct geni_se *se) > > { > > u32 proto = geni_se_read_proto(se); > > - u32 val; > > + u32 val, val_old; > > > > geni_se_irq_clear(se); > > > > - val = readl_relaxed(se->base + SE_GENI_M_IRQ_EN); > > if (proto != GENI_SE_UART) { > > + val_old = val = readl_relaxed(se->base + SE_GENI_M_IRQ_EN); > > val |= M_CMD_DONE_EN | M_TX_FIFO_WATERMARK_EN; > > val |= M_RX_FIFO_WATERMARK_EN | M_RX_FIFO_LAST_EN; > > - } > > - writel_relaxed(val, se->base + SE_GENI_M_IRQ_EN); > > + if (val != val_old) > > + writel_relaxed(val, se->base + SE_GENI_M_IRQ_EN); > > > > - val = readl_relaxed(se->base + SE_GENI_S_IRQ_EN); > > - if (proto != GENI_SE_UART) > > - val |= S_CMD_DONE_EN; > > - writel_relaxed(val, se->base + SE_GENI_S_IRQ_EN); > > + val = readl_relaxed(se->base + SE_GENI_S_IRQ_EN); > > Can we use the val_old trick here too? > > > + if (!(val & S_CMD_DONE_EN)) > > + writel_relaxed(val | S_CMD_DONE_EN, > > Because this val | S_CMD_DONE_EN thing is just hard to read :/ This is done in v2. Thanks for your review! -Doug
diff --git a/drivers/soc/qcom/qcom-geni-se.c b/drivers/soc/qcom/qcom-geni-se.c index 751a49f6534f..746854745b15 100644 --- a/drivers/soc/qcom/qcom-geni-se.c +++ b/drivers/soc/qcom/qcom-geni-se.c @@ -266,49 +266,53 @@ EXPORT_SYMBOL(geni_se_init); static void geni_se_select_fifo_mode(struct geni_se *se) { u32 proto = geni_se_read_proto(se); - u32 val; + u32 val, val_old; geni_se_irq_clear(se); - val = readl_relaxed(se->base + SE_GENI_M_IRQ_EN); if (proto != GENI_SE_UART) { + val_old = val = readl_relaxed(se->base + SE_GENI_M_IRQ_EN); val |= M_CMD_DONE_EN | M_TX_FIFO_WATERMARK_EN; val |= M_RX_FIFO_WATERMARK_EN | M_RX_FIFO_LAST_EN; - } - writel_relaxed(val, se->base + SE_GENI_M_IRQ_EN); + if (val != val_old) + writel_relaxed(val, se->base + SE_GENI_M_IRQ_EN); - val = readl_relaxed(se->base + SE_GENI_S_IRQ_EN); - if (proto != GENI_SE_UART) - val |= S_CMD_DONE_EN; - writel_relaxed(val, se->base + SE_GENI_S_IRQ_EN); + val = readl_relaxed(se->base + SE_GENI_S_IRQ_EN); + if (!(val & S_CMD_DONE_EN)) + writel_relaxed(val | S_CMD_DONE_EN, + se->base + SE_GENI_S_IRQ_EN); + } val = readl_relaxed(se->base + SE_GENI_DMA_MODE_EN); - val &= ~GENI_DMA_MODE_EN; - writel_relaxed(val, se->base + SE_GENI_DMA_MODE_EN); + if (val & GENI_DMA_MODE_EN) + writel_relaxed(val & ~GENI_DMA_MODE_EN, + se->base + SE_GENI_DMA_MODE_EN); } static void geni_se_select_dma_mode(struct geni_se *se) { u32 proto = geni_se_read_proto(se); - u32 val; + u32 val, val_old; geni_se_irq_clear(se); - val = readl_relaxed(se->base + SE_GENI_M_IRQ_EN); if (proto != GENI_SE_UART) { + val_old = val = readl_relaxed(se->base + SE_GENI_M_IRQ_EN); val &= ~(M_CMD_DONE_EN | M_TX_FIFO_WATERMARK_EN); val &= ~(M_RX_FIFO_WATERMARK_EN | M_RX_FIFO_LAST_EN); - } - writel_relaxed(val, se->base + SE_GENI_M_IRQ_EN); + if (val != val_old) + writel_relaxed(val, se->base + SE_GENI_M_IRQ_EN); - val = readl_relaxed(se->base + SE_GENI_S_IRQ_EN); - if (proto != GENI_SE_UART) - val &= ~S_CMD_DONE_EN; - writel_relaxed(val, se->base + SE_GENI_S_IRQ_EN); + val = readl_relaxed(se->base + SE_GENI_S_IRQ_EN); + if (val & S_CMD_DONE_EN) + writel_relaxed(val & ~S_CMD_DONE_EN, + se->base + SE_GENI_S_IRQ_EN); + } val = readl_relaxed(se->base + SE_GENI_DMA_MODE_EN); - val |= GENI_DMA_MODE_EN; - writel_relaxed(val, se->base + SE_GENI_DMA_MODE_EN); + if (!(val & GENI_DMA_MODE_EN)) + writel_relaxed(val | GENI_DMA_MODE_EN, + se->base + SE_GENI_DMA_MODE_EN); } /**
The functions geni_se_select_fifo_mode() and geni_se_select_fifo_mode() are a little funny. They read/write a bunch of memory mapped registers even if they don't change or aren't relevant for the current protocol. Let's make them a little more sane. NOTE: there is no evidence at all that this makes any performance difference and it fixes no bugs. However, it seems (to me) like it makes the functions a little easier to understand. Decreasing the amount of times we read/write memory mapped registers is also nice, even if we are using "relaxed" variants. Signed-off-by: Douglas Anderson <dianders@chromium.org> --- drivers/soc/qcom/qcom-geni-se.c | 44 ++++++++++++++++++--------------- 1 file changed, 24 insertions(+), 20 deletions(-)