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SubjectRe: [PATCH 2/2] tty: serial: qcom-geni-serial: check for valid size before starting dma
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On 07/03/2023 16:20, Konrad Dybcio wrote:
>
>
> On 7.03.2023 16:55, Srinivas Kandagatla wrote:
>> Check if there are valid length of bytes to transfer before starting dma.
>>
>> without this check we can see below kernel warning when we try to map a zero size buffers.
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 0 PID: 0 at drivers/iommu/dma-iommu.c:1046 iommu_dma_unmap_page+0xe0/0xfc
>> Modules linked in:
>> CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W 6.3.0-rc1-dirty #347
>> Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT)
>> pstate: 804000c5 (Nzcv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>> pc : iommu_dma_unmap_page+0xe0/0xfc
>> lr : iommu_dma_unmap_page+0x38/0xfc
>> ...
>> Call trace:
>> iommu_dma_unmap_page+0xe0/0xfc
>> dma_unmap_page_attrs+0x30/0x1ec
>> geni_se_tx_dma_unprep+0x58/0x80
>> qcom_geni_serial_isr+0x350/0x750
>> __handle_irq_event_percpu+0x58/0x148
>> handle_irq_event_percpu+0x18/0x4c
>> handle_irq_event+0x48/0x88
>> handle_fasteoi_irq+0xb0/0x130
>> generic_handle_domain_irq+0x2c/0x44
>> gic_handle_irq+0xd4/0x140
>> call_on_irq_stack+0x24/0x4c
>> do_interrupt_handler+0x80/0x84
>> el1_interrupt+0x38/0x6c
>> el1h_64_irq_handler+0x18/0x24
>> el1h_64_irq+0x64/0x68
>> cpuidle_enter_state+0x1e4/0x310
>> cpuidle_enter+0x3c/0x54
>> call_cpuidle+0x1c/0x40
>> do_idle+0x204/0x260
>> cpu_startup_entry+0x28/0x2c
>> kernel_init+0x0/0x12c
>> arch_post_acpi_subsys_init+0x0/0x8
>> start_kernel+0x3cc/0x74c
>> __primary_switched+0xbc/0xc4
>>
>> Fixes: 2aaa43c70778 ("tty: serial: qcom-geni-serial: add support for serial engine DMA")
>> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
> S-o-b but no C-d-b? Weird..
>
Yes, I did mess up this part.
thanks for spotting this, Will fix this in next spin!

--srini
>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>> ---
> Anyway, the change is good!
>
> Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
>
> Konrad
>> drivers/tty/serial/qcom_geni_serial.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
>> index 5972b5c317d3..bb63a00f4c07 100644
>> --- a/drivers/tty/serial/qcom_geni_serial.c
>> +++ b/drivers/tty/serial/qcom_geni_serial.c
>> @@ -637,6 +637,9 @@ static void qcom_geni_serial_start_tx_dma(struct uart_port *uport)
>>
>> xmit_size = CIRC_CNT_TO_END(xmit->head, xmit->tail, UART_XMIT_SIZE);
>>
>> + if (!xmit_size)
>> + return;
>> +
>> qcom_geni_serial_setup_tx(uport, xmit_size);
>>
>> ret = geni_se_tx_dma_prep(&port->se, &xmit->buf[xmit->tail],

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